src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java
changeset 47216 71c04702a3d5
parent 45910 c7092e4591b2
child 47248 22d665f53a4a
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,3941 @@
+/*
+ * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package com.sun.tools.javac.comp;
+
+import java.util.*;
+
+import javax.tools.JavaFileManager;
+
+import com.sun.tools.javac.code.*;
+import com.sun.tools.javac.code.Attribute.Compound;
+import com.sun.tools.javac.code.Directive.ExportsDirective;
+import com.sun.tools.javac.code.Directive.RequiresDirective;
+import com.sun.tools.javac.comp.Annotate.AnnotationTypeMetadata;
+import com.sun.tools.javac.jvm.*;
+import com.sun.tools.javac.resources.CompilerProperties.Errors;
+import com.sun.tools.javac.resources.CompilerProperties.Fragments;
+import com.sun.tools.javac.resources.CompilerProperties.Warnings;
+import com.sun.tools.javac.tree.*;
+import com.sun.tools.javac.util.*;
+import com.sun.tools.javac.util.JCDiagnostic.DiagnosticFlag;
+import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
+import com.sun.tools.javac.util.JCDiagnostic.Fragment;
+import com.sun.tools.javac.util.List;
+
+import com.sun.tools.javac.code.Lint;
+import com.sun.tools.javac.code.Lint.LintCategory;
+import com.sun.tools.javac.code.Scope.WriteableScope;
+import com.sun.tools.javac.code.Type.*;
+import com.sun.tools.javac.code.Symbol.*;
+import com.sun.tools.javac.comp.DeferredAttr.DeferredAttrContext;
+import com.sun.tools.javac.comp.Infer.FreeTypeListener;
+import com.sun.tools.javac.tree.JCTree.*;
+
+import static com.sun.tools.javac.code.Flags.*;
+import static com.sun.tools.javac.code.Flags.ANNOTATION;
+import static com.sun.tools.javac.code.Flags.SYNCHRONIZED;
+import static com.sun.tools.javac.code.Kinds.*;
+import static com.sun.tools.javac.code.Kinds.Kind.*;
+import static com.sun.tools.javac.code.Scope.LookupKind.NON_RECURSIVE;
+import static com.sun.tools.javac.code.TypeTag.*;
+import static com.sun.tools.javac.code.TypeTag.WILDCARD;
+
+import static com.sun.tools.javac.tree.JCTree.Tag.*;
+
+/** Type checking helper class for the attribution phase.
+ *
+ *  <p><b>This is NOT part of any supported API.
+ *  If you write code that depends on this, you do so at your own risk.
+ *  This code and its internal interfaces are subject to change or
+ *  deletion without notice.</b>
+ */
+public class Check {
+    protected static final Context.Key<Check> checkKey = new Context.Key<>();
+
+    private final Names names;
+    private final Log log;
+    private final Resolve rs;
+    private final Symtab syms;
+    private final Enter enter;
+    private final DeferredAttr deferredAttr;
+    private final Infer infer;
+    private final Types types;
+    private final TypeAnnotations typeAnnotations;
+    private final JCDiagnostic.Factory diags;
+    private final JavaFileManager fileManager;
+    private final Source source;
+    private final Profile profile;
+    private final boolean warnOnAnyAccessToMembers;
+
+    // The set of lint options currently in effect. It is initialized
+    // from the context, and then is set/reset as needed by Attr as it
+    // visits all the various parts of the trees during attribution.
+    private Lint lint;
+
+    // The method being analyzed in Attr - it is set/reset as needed by
+    // Attr as it visits new method declarations.
+    private MethodSymbol method;
+
+    public static Check instance(Context context) {
+        Check instance = context.get(checkKey);
+        if (instance == null)
+            instance = new Check(context);
+        return instance;
+    }
+
+    protected Check(Context context) {
+        context.put(checkKey, this);
+
+        names = Names.instance(context);
+        dfltTargetMeta = new Name[] { names.PACKAGE, names.TYPE,
+            names.FIELD, names.METHOD, names.CONSTRUCTOR,
+            names.ANNOTATION_TYPE, names.LOCAL_VARIABLE, names.PARAMETER};
+        log = Log.instance(context);
+        rs = Resolve.instance(context);
+        syms = Symtab.instance(context);
+        enter = Enter.instance(context);
+        deferredAttr = DeferredAttr.instance(context);
+        infer = Infer.instance(context);
+        types = Types.instance(context);
+        typeAnnotations = TypeAnnotations.instance(context);
+        diags = JCDiagnostic.Factory.instance(context);
+        Options options = Options.instance(context);
+        lint = Lint.instance(context);
+        fileManager = context.get(JavaFileManager.class);
+
+        source = Source.instance(context);
+        allowSimplifiedVarargs = source.allowSimplifiedVarargs();
+        allowDefaultMethods = source.allowDefaultMethods();
+        allowStrictMethodClashCheck = source.allowStrictMethodClashCheck();
+        allowPrivateSafeVarargs = source.allowPrivateSafeVarargs();
+        allowDiamondWithAnonymousClassCreation = source.allowDiamondWithAnonymousClassCreation();
+        warnOnAnyAccessToMembers = options.isSet("warnOnAccessToMembers");
+
+        Target target = Target.instance(context);
+        syntheticNameChar = target.syntheticNameChar();
+
+        profile = Profile.instance(context);
+
+        boolean verboseDeprecated = lint.isEnabled(LintCategory.DEPRECATION);
+        boolean verboseRemoval = lint.isEnabled(LintCategory.REMOVAL);
+        boolean verboseUnchecked = lint.isEnabled(LintCategory.UNCHECKED);
+        boolean enforceMandatoryWarnings = true;
+
+        deprecationHandler = new MandatoryWarningHandler(log, verboseDeprecated,
+                enforceMandatoryWarnings, "deprecated", LintCategory.DEPRECATION);
+        removalHandler = new MandatoryWarningHandler(log, verboseRemoval,
+                enforceMandatoryWarnings, "removal", LintCategory.REMOVAL);
+        uncheckedHandler = new MandatoryWarningHandler(log, verboseUnchecked,
+                enforceMandatoryWarnings, "unchecked", LintCategory.UNCHECKED);
+        sunApiHandler = new MandatoryWarningHandler(log, false,
+                enforceMandatoryWarnings, "sunapi", null);
+
+        deferredLintHandler = DeferredLintHandler.instance(context);
+    }
+
+    /** Switch: simplified varargs enabled?
+     */
+    boolean allowSimplifiedVarargs;
+
+    /** Switch: default methods enabled?
+     */
+    boolean allowDefaultMethods;
+
+    /** Switch: should unrelated return types trigger a method clash?
+     */
+    boolean allowStrictMethodClashCheck;
+
+    /** Switch: can the @SafeVarargs annotation be applied to private methods?
+     */
+    boolean allowPrivateSafeVarargs;
+
+    /** Switch: can diamond inference be used in anonymous instance creation ?
+     */
+    boolean allowDiamondWithAnonymousClassCreation;
+
+    /** Character for synthetic names
+     */
+    char syntheticNameChar;
+
+    /** A table mapping flat names of all compiled classes for each module in this run
+     *  to their symbols; maintained from outside.
+     */
+    private Map<Pair<ModuleSymbol, Name>,ClassSymbol> compiled = new HashMap<>();
+
+    /** A handler for messages about deprecated usage.
+     */
+    private MandatoryWarningHandler deprecationHandler;
+
+    /** A handler for messages about deprecated-for-removal usage.
+     */
+    private MandatoryWarningHandler removalHandler;
+
+    /** A handler for messages about unchecked or unsafe usage.
+     */
+    private MandatoryWarningHandler uncheckedHandler;
+
+    /** A handler for messages about using proprietary API.
+     */
+    private MandatoryWarningHandler sunApiHandler;
+
+    /** A handler for deferred lint warnings.
+     */
+    private DeferredLintHandler deferredLintHandler;
+
+/* *************************************************************************
+ * Errors and Warnings
+ **************************************************************************/
+
+    Lint setLint(Lint newLint) {
+        Lint prev = lint;
+        lint = newLint;
+        return prev;
+    }
+
+    MethodSymbol setMethod(MethodSymbol newMethod) {
+        MethodSymbol prev = method;
+        method = newMethod;
+        return prev;
+    }
+
+    /** Warn about deprecated symbol.
+     *  @param pos        Position to be used for error reporting.
+     *  @param sym        The deprecated symbol.
+     */
+    void warnDeprecated(DiagnosticPosition pos, Symbol sym) {
+        if (sym.isDeprecatedForRemoval()) {
+            if (!lint.isSuppressed(LintCategory.REMOVAL)) {
+                if (sym.kind == MDL) {
+                    removalHandler.report(pos, "has.been.deprecated.for.removal.module", sym);
+                } else {
+                    removalHandler.report(pos, "has.been.deprecated.for.removal", sym, sym.location());
+                }
+            }
+        } else if (!lint.isSuppressed(LintCategory.DEPRECATION)) {
+            if (sym.kind == MDL) {
+                deprecationHandler.report(pos, "has.been.deprecated.module", sym);
+            } else {
+                deprecationHandler.report(pos, "has.been.deprecated", sym, sym.location());
+            }
+        }
+    }
+
+    /** Warn about unchecked operation.
+     *  @param pos        Position to be used for error reporting.
+     *  @param msg        A string describing the problem.
+     */
+    public void warnUnchecked(DiagnosticPosition pos, String msg, Object... args) {
+        if (!lint.isSuppressed(LintCategory.UNCHECKED))
+            uncheckedHandler.report(pos, msg, args);
+    }
+
+    /** Warn about unsafe vararg method decl.
+     *  @param pos        Position to be used for error reporting.
+     */
+    void warnUnsafeVararg(DiagnosticPosition pos, String key, Object... args) {
+        if (lint.isEnabled(LintCategory.VARARGS) && allowSimplifiedVarargs)
+            log.warning(LintCategory.VARARGS, pos, key, args);
+    }
+
+    public void warnStatic(DiagnosticPosition pos, String msg, Object... args) {
+        if (lint.isEnabled(LintCategory.STATIC))
+            log.warning(LintCategory.STATIC, pos, msg, args);
+    }
+
+    /** Warn about division by integer constant zero.
+     *  @param pos        Position to be used for error reporting.
+     */
+    void warnDivZero(DiagnosticPosition pos) {
+        if (lint.isEnabled(LintCategory.DIVZERO))
+            log.warning(LintCategory.DIVZERO, pos, Warnings.DivZero);
+    }
+
+    /**
+     * Report any deferred diagnostics.
+     */
+    public void reportDeferredDiagnostics() {
+        deprecationHandler.reportDeferredDiagnostic();
+        removalHandler.reportDeferredDiagnostic();
+        uncheckedHandler.reportDeferredDiagnostic();
+        sunApiHandler.reportDeferredDiagnostic();
+    }
+
+
+    /** Report a failure to complete a class.
+     *  @param pos        Position to be used for error reporting.
+     *  @param ex         The failure to report.
+     */
+    public Type completionError(DiagnosticPosition pos, CompletionFailure ex) {
+        log.error(JCDiagnostic.DiagnosticFlag.NON_DEFERRABLE, pos, Errors.CantAccess(ex.sym, ex.getDetailValue()));
+        return syms.errType;
+    }
+
+    /** Report an error that wrong type tag was found.
+     *  @param pos        Position to be used for error reporting.
+     *  @param required   An internationalized string describing the type tag
+     *                    required.
+     *  @param found      The type that was found.
+     */
+    Type typeTagError(DiagnosticPosition pos, JCDiagnostic required, Object found) {
+        // this error used to be raised by the parser,
+        // but has been delayed to this point:
+        if (found instanceof Type && ((Type)found).hasTag(VOID)) {
+            log.error(pos, Errors.IllegalStartOfType);
+            return syms.errType;
+        }
+        log.error(pos, Errors.TypeFoundReq(found, required));
+        return types.createErrorType(found instanceof Type ? (Type)found : syms.errType);
+    }
+
+    /** Report an error that symbol cannot be referenced before super
+     *  has been called.
+     *  @param pos        Position to be used for error reporting.
+     *  @param sym        The referenced symbol.
+     */
+    void earlyRefError(DiagnosticPosition pos, Symbol sym) {
+        log.error(pos, Errors.CantRefBeforeCtorCalled(sym));
+    }
+
+    /** Report duplicate declaration error.
+     */
+    void duplicateError(DiagnosticPosition pos, Symbol sym) {
+        if (!sym.type.isErroneous()) {
+            Symbol location = sym.location();
+            if (location.kind == MTH &&
+                    ((MethodSymbol)location).isStaticOrInstanceInit()) {
+                log.error(pos,
+                          Errors.AlreadyDefinedInClinit(kindName(sym),
+                                                        sym,
+                                                        kindName(sym.location()),
+                                                        kindName(sym.location().enclClass()),
+                                                        sym.location().enclClass()));
+            } else {
+                log.error(pos,
+                          Errors.AlreadyDefined(kindName(sym),
+                                                sym,
+                                                kindName(sym.location()),
+                                                sym.location()));
+            }
+        }
+    }
+
+    /** Report array/varargs duplicate declaration
+     */
+    void varargsDuplicateError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
+        if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
+            log.error(pos, Errors.ArrayAndVarargs(sym1, sym2, sym2.location()));
+        }
+    }
+
+/* ************************************************************************
+ * duplicate declaration checking
+ *************************************************************************/
+
+    /** Check that variable does not hide variable with same name in
+     *  immediately enclosing local scope.
+     *  @param pos           Position for error reporting.
+     *  @param v             The symbol.
+     *  @param s             The scope.
+     */
+    void checkTransparentVar(DiagnosticPosition pos, VarSymbol v, Scope s) {
+        for (Symbol sym : s.getSymbolsByName(v.name)) {
+            if (sym.owner != v.owner) break;
+            if (sym.kind == VAR &&
+                sym.owner.kind.matches(KindSelector.VAL_MTH) &&
+                v.name != names.error) {
+                duplicateError(pos, sym);
+                return;
+            }
+        }
+    }
+
+    /** Check that a class or interface does not hide a class or
+     *  interface with same name in immediately enclosing local scope.
+     *  @param pos           Position for error reporting.
+     *  @param c             The symbol.
+     *  @param s             The scope.
+     */
+    void checkTransparentClass(DiagnosticPosition pos, ClassSymbol c, Scope s) {
+        for (Symbol sym : s.getSymbolsByName(c.name)) {
+            if (sym.owner != c.owner) break;
+            if (sym.kind == TYP && !sym.type.hasTag(TYPEVAR) &&
+                sym.owner.kind.matches(KindSelector.VAL_MTH) &&
+                c.name != names.error) {
+                duplicateError(pos, sym);
+                return;
+            }
+        }
+    }
+
+    /** Check that class does not have the same name as one of
+     *  its enclosing classes, or as a class defined in its enclosing scope.
+     *  return true if class is unique in its enclosing scope.
+     *  @param pos           Position for error reporting.
+     *  @param name          The class name.
+     *  @param s             The enclosing scope.
+     */
+    boolean checkUniqueClassName(DiagnosticPosition pos, Name name, Scope s) {
+        for (Symbol sym : s.getSymbolsByName(name, NON_RECURSIVE)) {
+            if (sym.kind == TYP && sym.name != names.error) {
+                duplicateError(pos, sym);
+                return false;
+            }
+        }
+        for (Symbol sym = s.owner; sym != null; sym = sym.owner) {
+            if (sym.kind == TYP && sym.name == name && sym.name != names.error) {
+                duplicateError(pos, sym);
+                return true;
+            }
+        }
+        return true;
+    }
+
+/* *************************************************************************
+ * Class name generation
+ **************************************************************************/
+
+
+    private Map<Pair<Name, Name>, Integer> localClassNameIndexes = new HashMap<>();
+
+    /** Return name of local class.
+     *  This is of the form   {@code <enclClass> $ n <classname> }
+     *  where
+     *    enclClass is the flat name of the enclosing class,
+     *    classname is the simple name of the local class
+     */
+    Name localClassName(ClassSymbol c) {
+        Name enclFlatname = c.owner.enclClass().flatname;
+        String enclFlatnameStr = enclFlatname.toString();
+        Pair<Name, Name> key = new Pair<>(enclFlatname, c.name);
+        Integer index = localClassNameIndexes.get(key);
+        for (int i = (index == null) ? 1 : index; ; i++) {
+            Name flatname = names.fromString(enclFlatnameStr
+                    + syntheticNameChar + i + c.name);
+            if (getCompiled(c.packge().modle, flatname) == null) {
+                localClassNameIndexes.put(key, i + 1);
+                return flatname;
+            }
+        }
+    }
+
+    void clearLocalClassNameIndexes(ClassSymbol c) {
+        if (c.owner != null && c.owner.kind != NIL) {
+            localClassNameIndexes.remove(new Pair<>(
+                    c.owner.enclClass().flatname, c.name));
+        }
+    }
+
+    public void newRound() {
+        compiled.clear();
+        localClassNameIndexes.clear();
+    }
+
+    public void putCompiled(ClassSymbol csym) {
+        compiled.put(Pair.of(csym.packge().modle, csym.flatname), csym);
+    }
+
+    public ClassSymbol getCompiled(ClassSymbol csym) {
+        return compiled.get(Pair.of(csym.packge().modle, csym.flatname));
+    }
+
+    public ClassSymbol getCompiled(ModuleSymbol msym, Name flatname) {
+        return compiled.get(Pair.of(msym, flatname));
+    }
+
+    public void removeCompiled(ClassSymbol csym) {
+        compiled.remove(Pair.of(csym.packge().modle, csym.flatname));
+    }
+
+/* *************************************************************************
+ * Type Checking
+ **************************************************************************/
+
+    /**
+     * A check context is an object that can be used to perform compatibility
+     * checks - depending on the check context, meaning of 'compatibility' might
+     * vary significantly.
+     */
+    public interface CheckContext {
+        /**
+         * Is type 'found' compatible with type 'req' in given context
+         */
+        boolean compatible(Type found, Type req, Warner warn);
+        /**
+         * Report a check error
+         */
+        void report(DiagnosticPosition pos, JCDiagnostic details);
+        /**
+         * Obtain a warner for this check context
+         */
+        public Warner checkWarner(DiagnosticPosition pos, Type found, Type req);
+
+        public InferenceContext inferenceContext();
+
+        public DeferredAttr.DeferredAttrContext deferredAttrContext();
+    }
+
+    /**
+     * This class represent a check context that is nested within another check
+     * context - useful to check sub-expressions. The default behavior simply
+     * redirects all method calls to the enclosing check context leveraging
+     * the forwarding pattern.
+     */
+    static class NestedCheckContext implements CheckContext {
+        CheckContext enclosingContext;
+
+        NestedCheckContext(CheckContext enclosingContext) {
+            this.enclosingContext = enclosingContext;
+        }
+
+        public boolean compatible(Type found, Type req, Warner warn) {
+            return enclosingContext.compatible(found, req, warn);
+        }
+
+        public void report(DiagnosticPosition pos, JCDiagnostic details) {
+            enclosingContext.report(pos, details);
+        }
+
+        public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
+            return enclosingContext.checkWarner(pos, found, req);
+        }
+
+        public InferenceContext inferenceContext() {
+            return enclosingContext.inferenceContext();
+        }
+
+        public DeferredAttrContext deferredAttrContext() {
+            return enclosingContext.deferredAttrContext();
+        }
+    }
+
+    /**
+     * Check context to be used when evaluating assignment/return statements
+     */
+    CheckContext basicHandler = new CheckContext() {
+        public void report(DiagnosticPosition pos, JCDiagnostic details) {
+            log.error(pos, Errors.ProbFoundReq(details));
+        }
+        public boolean compatible(Type found, Type req, Warner warn) {
+            return types.isAssignable(found, req, warn);
+        }
+
+        public Warner checkWarner(DiagnosticPosition pos, Type found, Type req) {
+            return convertWarner(pos, found, req);
+        }
+
+        public InferenceContext inferenceContext() {
+            return infer.emptyContext;
+        }
+
+        public DeferredAttrContext deferredAttrContext() {
+            return deferredAttr.emptyDeferredAttrContext;
+        }
+
+        @Override
+        public String toString() {
+            return "CheckContext: basicHandler";
+        }
+    };
+
+    /** Check that a given type is assignable to a given proto-type.
+     *  If it is, return the type, otherwise return errType.
+     *  @param pos        Position to be used for error reporting.
+     *  @param found      The type that was found.
+     *  @param req        The type that was required.
+     */
+    public Type checkType(DiagnosticPosition pos, Type found, Type req) {
+        return checkType(pos, found, req, basicHandler);
+    }
+
+    Type checkType(final DiagnosticPosition pos, final Type found, final Type req, final CheckContext checkContext) {
+        final InferenceContext inferenceContext = checkContext.inferenceContext();
+        if (inferenceContext.free(req) || inferenceContext.free(found)) {
+            inferenceContext.addFreeTypeListener(List.of(req, found),
+                    solvedContext -> checkType(pos, solvedContext.asInstType(found), solvedContext.asInstType(req), checkContext));
+        }
+        if (req.hasTag(ERROR))
+            return req;
+        if (req.hasTag(NONE))
+            return found;
+        if (checkContext.compatible(found, req, checkContext.checkWarner(pos, found, req))) {
+            return found;
+        } else {
+            if (found.isNumeric() && req.isNumeric()) {
+                checkContext.report(pos, diags.fragment(Fragments.PossibleLossOfPrecision(found, req)));
+                return types.createErrorType(found);
+            }
+            checkContext.report(pos, diags.fragment(Fragments.InconvertibleTypes(found, req)));
+            return types.createErrorType(found);
+        }
+    }
+
+    /** Check that a given type can be cast to a given target type.
+     *  Return the result of the cast.
+     *  @param pos        Position to be used for error reporting.
+     *  @param found      The type that is being cast.
+     *  @param req        The target type of the cast.
+     */
+    Type checkCastable(DiagnosticPosition pos, Type found, Type req) {
+        return checkCastable(pos, found, req, basicHandler);
+    }
+    Type checkCastable(DiagnosticPosition pos, Type found, Type req, CheckContext checkContext) {
+        if (types.isCastable(found, req, castWarner(pos, found, req))) {
+            return req;
+        } else {
+            checkContext.report(pos, diags.fragment(Fragments.InconvertibleTypes(found, req)));
+            return types.createErrorType(found);
+        }
+    }
+
+    /** Check for redundant casts (i.e. where source type is a subtype of target type)
+     * The problem should only be reported for non-292 cast
+     */
+    public void checkRedundantCast(Env<AttrContext> env, final JCTypeCast tree) {
+        if (!tree.type.isErroneous()
+                && types.isSameType(tree.expr.type, tree.clazz.type)
+                && !(ignoreAnnotatedCasts && TreeInfo.containsTypeAnnotation(tree.clazz))
+                && !is292targetTypeCast(tree)) {
+            deferredLintHandler.report(() -> {
+                if (lint.isEnabled(LintCategory.CAST))
+                    log.warning(LintCategory.CAST,
+                            tree.pos(), Warnings.RedundantCast(tree.clazz.type));
+            });
+        }
+    }
+    //where
+        private boolean is292targetTypeCast(JCTypeCast tree) {
+            boolean is292targetTypeCast = false;
+            JCExpression expr = TreeInfo.skipParens(tree.expr);
+            if (expr.hasTag(APPLY)) {
+                JCMethodInvocation apply = (JCMethodInvocation)expr;
+                Symbol sym = TreeInfo.symbol(apply.meth);
+                is292targetTypeCast = sym != null &&
+                    sym.kind == MTH &&
+                    (sym.flags() & HYPOTHETICAL) != 0;
+            }
+            return is292targetTypeCast;
+        }
+
+        private static final boolean ignoreAnnotatedCasts = true;
+
+    /** Check that a type is within some bounds.
+     *
+     *  Used in TypeApply to verify that, e.g., X in {@code V<X>} is a valid
+     *  type argument.
+     *  @param a             The type that should be bounded by bs.
+     *  @param bound         The bound.
+     */
+    private boolean checkExtends(Type a, Type bound) {
+         if (a.isUnbound()) {
+             return true;
+         } else if (!a.hasTag(WILDCARD)) {
+             a = types.cvarUpperBound(a);
+             return types.isSubtype(a, bound);
+         } else if (a.isExtendsBound()) {
+             return types.isCastable(bound, types.wildUpperBound(a), types.noWarnings);
+         } else if (a.isSuperBound()) {
+             return !types.notSoftSubtype(types.wildLowerBound(a), bound);
+         }
+         return true;
+     }
+
+    /** Check that type is different from 'void'.
+     *  @param pos           Position to be used for error reporting.
+     *  @param t             The type to be checked.
+     */
+    Type checkNonVoid(DiagnosticPosition pos, Type t) {
+        if (t.hasTag(VOID)) {
+            log.error(pos, Errors.VoidNotAllowedHere);
+            return types.createErrorType(t);
+        } else {
+            return t;
+        }
+    }
+
+    Type checkClassOrArrayType(DiagnosticPosition pos, Type t) {
+        if (!t.hasTag(CLASS) && !t.hasTag(ARRAY) && !t.hasTag(ERROR)) {
+            return typeTagError(pos,
+                                diags.fragment(Fragments.TypeReqClassArray),
+                                asTypeParam(t));
+        } else {
+            return t;
+        }
+    }
+
+    /** Check that type is a class or interface type.
+     *  @param pos           Position to be used for error reporting.
+     *  @param t             The type to be checked.
+     */
+    Type checkClassType(DiagnosticPosition pos, Type t) {
+        if (!t.hasTag(CLASS) && !t.hasTag(ERROR)) {
+            return typeTagError(pos,
+                                diags.fragment(Fragments.TypeReqClass),
+                                asTypeParam(t));
+        } else {
+            return t;
+        }
+    }
+    //where
+        private Object asTypeParam(Type t) {
+            return (t.hasTag(TYPEVAR))
+                                    ? diags.fragment(Fragments.TypeParameter(t))
+                                    : t;
+        }
+
+    /** Check that type is a valid qualifier for a constructor reference expression
+     */
+    Type checkConstructorRefType(DiagnosticPosition pos, Type t) {
+        t = checkClassOrArrayType(pos, t);
+        if (t.hasTag(CLASS)) {
+            if ((t.tsym.flags() & (ABSTRACT | INTERFACE)) != 0) {
+                log.error(pos, Errors.AbstractCantBeInstantiated(t.tsym));
+                t = types.createErrorType(t);
+            } else if ((t.tsym.flags() & ENUM) != 0) {
+                log.error(pos, Errors.EnumCantBeInstantiated);
+                t = types.createErrorType(t);
+            } else {
+                t = checkClassType(pos, t, true);
+            }
+        } else if (t.hasTag(ARRAY)) {
+            if (!types.isReifiable(((ArrayType)t).elemtype)) {
+                log.error(pos, Errors.GenericArrayCreation);
+                t = types.createErrorType(t);
+            }
+        }
+        return t;
+    }
+
+    /** Check that type is a class or interface type.
+     *  @param pos           Position to be used for error reporting.
+     *  @param t             The type to be checked.
+     *  @param noBounds    True if type bounds are illegal here.
+     */
+    Type checkClassType(DiagnosticPosition pos, Type t, boolean noBounds) {
+        t = checkClassType(pos, t);
+        if (noBounds && t.isParameterized()) {
+            List<Type> args = t.getTypeArguments();
+            while (args.nonEmpty()) {
+                if (args.head.hasTag(WILDCARD))
+                    return typeTagError(pos,
+                                        diags.fragment(Fragments.TypeReqExact),
+                                        args.head);
+                args = args.tail;
+            }
+        }
+        return t;
+    }
+
+    /** Check that type is a reference type, i.e. a class, interface or array type
+     *  or a type variable.
+     *  @param pos           Position to be used for error reporting.
+     *  @param t             The type to be checked.
+     */
+    Type checkRefType(DiagnosticPosition pos, Type t) {
+        if (t.isReference())
+            return t;
+        else
+            return typeTagError(pos,
+                                diags.fragment(Fragments.TypeReqRef),
+                                t);
+    }
+
+    /** Check that each type is a reference type, i.e. a class, interface or array type
+     *  or a type variable.
+     *  @param trees         Original trees, used for error reporting.
+     *  @param types         The types to be checked.
+     */
+    List<Type> checkRefTypes(List<JCExpression> trees, List<Type> types) {
+        List<JCExpression> tl = trees;
+        for (List<Type> l = types; l.nonEmpty(); l = l.tail) {
+            l.head = checkRefType(tl.head.pos(), l.head);
+            tl = tl.tail;
+        }
+        return types;
+    }
+
+    /** Check that type is a null or reference type.
+     *  @param pos           Position to be used for error reporting.
+     *  @param t             The type to be checked.
+     */
+    Type checkNullOrRefType(DiagnosticPosition pos, Type t) {
+        if (t.isReference() || t.hasTag(BOT))
+            return t;
+        else
+            return typeTagError(pos,
+                                diags.fragment(Fragments.TypeReqRef),
+                                t);
+    }
+
+    /** Check that flag set does not contain elements of two conflicting sets. s
+     *  Return true if it doesn't.
+     *  @param pos           Position to be used for error reporting.
+     *  @param flags         The set of flags to be checked.
+     *  @param set1          Conflicting flags set #1.
+     *  @param set2          Conflicting flags set #2.
+     */
+    boolean checkDisjoint(DiagnosticPosition pos, long flags, long set1, long set2) {
+        if ((flags & set1) != 0 && (flags & set2) != 0) {
+            log.error(pos,
+                      Errors.IllegalCombinationOfModifiers(asFlagSet(TreeInfo.firstFlag(flags & set1)),
+                                                           asFlagSet(TreeInfo.firstFlag(flags & set2))));
+            return false;
+        } else
+            return true;
+    }
+
+    /** Check that usage of diamond operator is correct (i.e. diamond should not
+     * be used with non-generic classes or in anonymous class creation expressions)
+     */
+    Type checkDiamond(JCNewClass tree, Type t) {
+        if (!TreeInfo.isDiamond(tree) ||
+                t.isErroneous()) {
+            return checkClassType(tree.clazz.pos(), t, true);
+        } else {
+            if (tree.def != null && !allowDiamondWithAnonymousClassCreation) {
+                log.error(DiagnosticFlag.SOURCE_LEVEL, tree.clazz.pos(),
+                        Errors.CantApplyDiamond1(t, Fragments.DiamondAndAnonClassNotSupportedInSource(source.name)));
+            }
+            if (t.tsym.type.getTypeArguments().isEmpty()) {
+                log.error(tree.clazz.pos(),
+                          Errors.CantApplyDiamond1(t,
+                                                   Fragments.DiamondNonGeneric(t)));
+                return types.createErrorType(t);
+            } else if (tree.typeargs != null &&
+                    tree.typeargs.nonEmpty()) {
+                log.error(tree.clazz.pos(),
+                          Errors.CantApplyDiamond1(t,
+                                                   Fragments.DiamondAndExplicitParams(t)));
+                return types.createErrorType(t);
+            } else {
+                return t;
+            }
+        }
+    }
+
+    /** Check that the type inferred using the diamond operator does not contain
+     *  non-denotable types such as captured types or intersection types.
+     *  @param t the type inferred using the diamond operator
+     *  @return  the (possibly empty) list of non-denotable types.
+     */
+    List<Type> checkDiamondDenotable(ClassType t) {
+        ListBuffer<Type> buf = new ListBuffer<>();
+        for (Type arg : t.allparams()) {
+            if (!diamondTypeChecker.visit(arg, null)) {
+                buf.append(arg);
+            }
+        }
+        return buf.toList();
+    }
+        // where
+
+        /** diamondTypeChecker: A type visitor that descends down the given type looking for non-denotable
+         *  types. The visit methods return false as soon as a non-denotable type is encountered and true
+         *  otherwise.
+         */
+        private static final Types.SimpleVisitor<Boolean, Void> diamondTypeChecker = new Types.SimpleVisitor<Boolean, Void>() {
+            @Override
+            public Boolean visitType(Type t, Void s) {
+                return true;
+            }
+            @Override
+            public Boolean visitClassType(ClassType t, Void s) {
+                if (t.isCompound()) {
+                    return false;
+                }
+                for (Type targ : t.allparams()) {
+                    if (!visit(targ, s)) {
+                        return false;
+                    }
+                }
+                return true;
+            }
+
+            @Override
+            public Boolean visitTypeVar(TypeVar t, Void s) {
+                /* Any type variable mentioned in the inferred type must have been declared as a type parameter
+                  (i.e cannot have been produced by inference (18.4))
+                */
+                return t.tsym.owner.type.getTypeArguments().contains(t);
+            }
+
+            @Override
+            public Boolean visitCapturedType(CapturedType t, Void s) {
+                /* Any type variable mentioned in the inferred type must have been declared as a type parameter
+                  (i.e cannot have been produced by capture conversion (5.1.10))
+                */
+                return false;
+            }
+
+            @Override
+            public Boolean visitArrayType(ArrayType t, Void s) {
+                return visit(t.elemtype, s);
+            }
+
+            @Override
+            public Boolean visitWildcardType(WildcardType t, Void s) {
+                return visit(t.type, s);
+            }
+        };
+
+    void checkVarargsMethodDecl(Env<AttrContext> env, JCMethodDecl tree) {
+        MethodSymbol m = tree.sym;
+        if (!allowSimplifiedVarargs) return;
+        boolean hasTrustMeAnno = m.attribute(syms.trustMeType.tsym) != null;
+        Type varargElemType = null;
+        if (m.isVarArgs()) {
+            varargElemType = types.elemtype(tree.params.last().type);
+        }
+        if (hasTrustMeAnno && !isTrustMeAllowedOnMethod(m)) {
+            if (varargElemType != null) {
+                JCDiagnostic msg = allowPrivateSafeVarargs ?
+                        diags.fragment(Fragments.VarargsTrustmeOnVirtualVarargs(m)) :
+                        diags.fragment(Fragments.VarargsTrustmeOnVirtualVarargsFinalOnly(m));
+                log.error(tree,
+                          Errors.VarargsInvalidTrustmeAnno(syms.trustMeType.tsym,
+                                                           msg));
+            } else {
+                log.error(tree,
+                          Errors.VarargsInvalidTrustmeAnno(syms.trustMeType.tsym,
+                                                           Fragments.VarargsTrustmeOnNonVarargsMeth(m)));
+            }
+        } else if (hasTrustMeAnno && varargElemType != null &&
+                            types.isReifiable(varargElemType)) {
+            warnUnsafeVararg(tree,
+                            "varargs.redundant.trustme.anno",
+                            syms.trustMeType.tsym,
+                            diags.fragment(Fragments.VarargsTrustmeOnReifiableVarargs(varargElemType)));
+        }
+        else if (!hasTrustMeAnno && varargElemType != null &&
+                !types.isReifiable(varargElemType)) {
+            warnUnchecked(tree.params.head.pos(), "unchecked.varargs.non.reifiable.type", varargElemType);
+        }
+    }
+    //where
+        private boolean isTrustMeAllowedOnMethod(Symbol s) {
+            return (s.flags() & VARARGS) != 0 &&
+                (s.isConstructor() ||
+                    (s.flags() & (STATIC | FINAL |
+                                  (allowPrivateSafeVarargs ? PRIVATE : 0) )) != 0);
+        }
+
+    Type checkMethod(final Type mtype,
+            final Symbol sym,
+            final Env<AttrContext> env,
+            final List<JCExpression> argtrees,
+            final List<Type> argtypes,
+            final boolean useVarargs,
+            InferenceContext inferenceContext) {
+        // System.out.println("call   : " + env.tree);
+        // System.out.println("method : " + owntype);
+        // System.out.println("actuals: " + argtypes);
+        if (inferenceContext.free(mtype)) {
+            inferenceContext.addFreeTypeListener(List.of(mtype),
+                    solvedContext -> checkMethod(solvedContext.asInstType(mtype), sym, env, argtrees, argtypes, useVarargs, solvedContext));
+            return mtype;
+        }
+        Type owntype = mtype;
+        List<Type> formals = owntype.getParameterTypes();
+        List<Type> nonInferred = sym.type.getParameterTypes();
+        if (nonInferred.length() != formals.length()) nonInferred = formals;
+        Type last = useVarargs ? formals.last() : null;
+        if (sym.name == names.init && sym.owner == syms.enumSym) {
+            formals = formals.tail.tail;
+            nonInferred = nonInferred.tail.tail;
+        }
+        List<JCExpression> args = argtrees;
+        if (args != null) {
+            //this is null when type-checking a method reference
+            while (formals.head != last) {
+                JCTree arg = args.head;
+                Warner warn = convertWarner(arg.pos(), arg.type, nonInferred.head);
+                assertConvertible(arg, arg.type, formals.head, warn);
+                args = args.tail;
+                formals = formals.tail;
+                nonInferred = nonInferred.tail;
+            }
+            if (useVarargs) {
+                Type varArg = types.elemtype(last);
+                while (args.tail != null) {
+                    JCTree arg = args.head;
+                    Warner warn = convertWarner(arg.pos(), arg.type, varArg);
+                    assertConvertible(arg, arg.type, varArg, warn);
+                    args = args.tail;
+                }
+            } else if ((sym.flags() & (VARARGS | SIGNATURE_POLYMORPHIC)) == VARARGS) {
+                // non-varargs call to varargs method
+                Type varParam = owntype.getParameterTypes().last();
+                Type lastArg = argtypes.last();
+                if (types.isSubtypeUnchecked(lastArg, types.elemtype(varParam)) &&
+                    !types.isSameType(types.erasure(varParam), types.erasure(lastArg)))
+                    log.warning(argtrees.last().pos(),
+                                Warnings.InexactNonVarargsCall(types.elemtype(varParam),varParam));
+            }
+        }
+        if (useVarargs) {
+            Type argtype = owntype.getParameterTypes().last();
+            if (!types.isReifiable(argtype) &&
+                (!allowSimplifiedVarargs ||
+                 sym.baseSymbol().attribute(syms.trustMeType.tsym) == null ||
+                 !isTrustMeAllowedOnMethod(sym))) {
+                warnUnchecked(env.tree.pos(),
+                                  "unchecked.generic.array.creation",
+                                  argtype);
+            }
+            if ((sym.baseSymbol().flags() & SIGNATURE_POLYMORPHIC) == 0) {
+                TreeInfo.setVarargsElement(env.tree, types.elemtype(argtype));
+            }
+         }
+         return owntype;
+    }
+    //where
+    private void assertConvertible(JCTree tree, Type actual, Type formal, Warner warn) {
+        if (types.isConvertible(actual, formal, warn))
+            return;
+
+        if (formal.isCompound()
+            && types.isSubtype(actual, types.supertype(formal))
+            && types.isSubtypeUnchecked(actual, types.interfaces(formal), warn))
+            return;
+    }
+
+    /**
+     * Check that type 't' is a valid instantiation of a generic class
+     * (see JLS 4.5)
+     *
+     * @param t class type to be checked
+     * @return true if 't' is well-formed
+     */
+    public boolean checkValidGenericType(Type t) {
+        return firstIncompatibleTypeArg(t) == null;
+    }
+    //WHERE
+        private Type firstIncompatibleTypeArg(Type type) {
+            List<Type> formals = type.tsym.type.allparams();
+            List<Type> actuals = type.allparams();
+            List<Type> args = type.getTypeArguments();
+            List<Type> forms = type.tsym.type.getTypeArguments();
+            ListBuffer<Type> bounds_buf = new ListBuffer<>();
+
+            // For matching pairs of actual argument types `a' and
+            // formal type parameters with declared bound `b' ...
+            while (args.nonEmpty() && forms.nonEmpty()) {
+                // exact type arguments needs to know their
+                // bounds (for upper and lower bound
+                // calculations).  So we create new bounds where
+                // type-parameters are replaced with actuals argument types.
+                bounds_buf.append(types.subst(forms.head.getUpperBound(), formals, actuals));
+                args = args.tail;
+                forms = forms.tail;
+            }
+
+            args = type.getTypeArguments();
+            List<Type> tvars_cap = types.substBounds(formals,
+                                      formals,
+                                      types.capture(type).allparams());
+            while (args.nonEmpty() && tvars_cap.nonEmpty()) {
+                // Let the actual arguments know their bound
+                args.head.withTypeVar((TypeVar)tvars_cap.head);
+                args = args.tail;
+                tvars_cap = tvars_cap.tail;
+            }
+
+            args = type.getTypeArguments();
+            List<Type> bounds = bounds_buf.toList();
+
+            while (args.nonEmpty() && bounds.nonEmpty()) {
+                Type actual = args.head;
+                if (!isTypeArgErroneous(actual) &&
+                        !bounds.head.isErroneous() &&
+                        !checkExtends(actual, bounds.head)) {
+                    return args.head;
+                }
+                args = args.tail;
+                bounds = bounds.tail;
+            }
+
+            args = type.getTypeArguments();
+            bounds = bounds_buf.toList();
+
+            for (Type arg : types.capture(type).getTypeArguments()) {
+                if (arg.hasTag(TYPEVAR) &&
+                        arg.getUpperBound().isErroneous() &&
+                        !bounds.head.isErroneous() &&
+                        !isTypeArgErroneous(args.head)) {
+                    return args.head;
+                }
+                bounds = bounds.tail;
+                args = args.tail;
+            }
+
+            return null;
+        }
+        //where
+        boolean isTypeArgErroneous(Type t) {
+            return isTypeArgErroneous.visit(t);
+        }
+
+        Types.UnaryVisitor<Boolean> isTypeArgErroneous = new Types.UnaryVisitor<Boolean>() {
+            public Boolean visitType(Type t, Void s) {
+                return t.isErroneous();
+            }
+            @Override
+            public Boolean visitTypeVar(TypeVar t, Void s) {
+                return visit(t.getUpperBound());
+            }
+            @Override
+            public Boolean visitCapturedType(CapturedType t, Void s) {
+                return visit(t.getUpperBound()) ||
+                        visit(t.getLowerBound());
+            }
+            @Override
+            public Boolean visitWildcardType(WildcardType t, Void s) {
+                return visit(t.type);
+            }
+        };
+
+    /** Check that given modifiers are legal for given symbol and
+     *  return modifiers together with any implicit modifiers for that symbol.
+     *  Warning: we can't use flags() here since this method
+     *  is called during class enter, when flags() would cause a premature
+     *  completion.
+     *  @param pos           Position to be used for error reporting.
+     *  @param flags         The set of modifiers given in a definition.
+     *  @param sym           The defined symbol.
+     */
+    long checkFlags(DiagnosticPosition pos, long flags, Symbol sym, JCTree tree) {
+        long mask;
+        long implicit = 0;
+
+        switch (sym.kind) {
+        case VAR:
+            if (TreeInfo.isReceiverParam(tree))
+                mask = ReceiverParamFlags;
+            else if (sym.owner.kind != TYP)
+                mask = LocalVarFlags;
+            else if ((sym.owner.flags_field & INTERFACE) != 0)
+                mask = implicit = InterfaceVarFlags;
+            else
+                mask = VarFlags;
+            break;
+        case MTH:
+            if (sym.name == names.init) {
+                if ((sym.owner.flags_field & ENUM) != 0) {
+                    // enum constructors cannot be declared public or
+                    // protected and must be implicitly or explicitly
+                    // private
+                    implicit = PRIVATE;
+                    mask = PRIVATE;
+                } else
+                    mask = ConstructorFlags;
+            }  else if ((sym.owner.flags_field & INTERFACE) != 0) {
+                if ((sym.owner.flags_field & ANNOTATION) != 0) {
+                    mask = AnnotationTypeElementMask;
+                    implicit = PUBLIC | ABSTRACT;
+                } else if ((flags & (DEFAULT | STATIC | PRIVATE)) != 0) {
+                    mask = InterfaceMethodMask;
+                    implicit = (flags & PRIVATE) != 0 ? 0 : PUBLIC;
+                    if ((flags & DEFAULT) != 0) {
+                        implicit |= ABSTRACT;
+                    }
+                } else {
+                    mask = implicit = InterfaceMethodFlags;
+                }
+            } else {
+                mask = MethodFlags;
+            }
+            // Imply STRICTFP if owner has STRICTFP set.
+            if (((flags|implicit) & Flags.ABSTRACT) == 0 ||
+                ((flags) & Flags.DEFAULT) != 0)
+                implicit |= sym.owner.flags_field & STRICTFP;
+            break;
+        case TYP:
+            if (sym.isLocal()) {
+                mask = LocalClassFlags;
+                if ((sym.owner.flags_field & STATIC) == 0 &&
+                    (flags & ENUM) != 0)
+                    log.error(pos, Errors.EnumsMustBeStatic);
+            } else if (sym.owner.kind == TYP) {
+                mask = MemberClassFlags;
+                if (sym.owner.owner.kind == PCK ||
+                    (sym.owner.flags_field & STATIC) != 0)
+                    mask |= STATIC;
+                else if ((flags & ENUM) != 0)
+                    log.error(pos, Errors.EnumsMustBeStatic);
+                // Nested interfaces and enums are always STATIC (Spec ???)
+                if ((flags & (INTERFACE | ENUM)) != 0 ) implicit = STATIC;
+            } else {
+                mask = ClassFlags;
+            }
+            // Interfaces are always ABSTRACT
+            if ((flags & INTERFACE) != 0) implicit |= ABSTRACT;
+
+            if ((flags & ENUM) != 0) {
+                // enums can't be declared abstract or final
+                mask &= ~(ABSTRACT | FINAL);
+                implicit |= implicitEnumFinalFlag(tree);
+            }
+            // Imply STRICTFP if owner has STRICTFP set.
+            implicit |= sym.owner.flags_field & STRICTFP;
+            break;
+        default:
+            throw new AssertionError();
+        }
+        long illegal = flags & ExtendedStandardFlags & ~mask;
+        if (illegal != 0) {
+            if ((illegal & INTERFACE) != 0) {
+                log.error(pos, ((flags & ANNOTATION) != 0) ? Errors.AnnotationDeclNotAllowedHere : Errors.IntfNotAllowedHere);
+                mask |= INTERFACE;
+            }
+            else {
+                log.error(pos,
+                          Errors.ModNotAllowedHere(asFlagSet(illegal)));
+            }
+        }
+        else if ((sym.kind == TYP ||
+                  // ISSUE: Disallowing abstract&private is no longer appropriate
+                  // in the presence of inner classes. Should it be deleted here?
+                  checkDisjoint(pos, flags,
+                                ABSTRACT,
+                                PRIVATE | STATIC | DEFAULT))
+                 &&
+                 checkDisjoint(pos, flags,
+                                STATIC | PRIVATE,
+                                DEFAULT)
+                 &&
+                 checkDisjoint(pos, flags,
+                               ABSTRACT | INTERFACE,
+                               FINAL | NATIVE | SYNCHRONIZED)
+                 &&
+                 checkDisjoint(pos, flags,
+                               PUBLIC,
+                               PRIVATE | PROTECTED)
+                 &&
+                 checkDisjoint(pos, flags,
+                               PRIVATE,
+                               PUBLIC | PROTECTED)
+                 &&
+                 checkDisjoint(pos, flags,
+                               FINAL,
+                               VOLATILE)
+                 &&
+                 (sym.kind == TYP ||
+                  checkDisjoint(pos, flags,
+                                ABSTRACT | NATIVE,
+                                STRICTFP))) {
+            // skip
+        }
+        return flags & (mask | ~ExtendedStandardFlags) | implicit;
+    }
+
+
+    /** Determine if this enum should be implicitly final.
+     *
+     *  If the enum has no specialized enum contants, it is final.
+     *
+     *  If the enum does have specialized enum contants, it is
+     *  <i>not</i> final.
+     */
+    private long implicitEnumFinalFlag(JCTree tree) {
+        if (!tree.hasTag(CLASSDEF)) return 0;
+        class SpecialTreeVisitor extends JCTree.Visitor {
+            boolean specialized;
+            SpecialTreeVisitor() {
+                this.specialized = false;
+            }
+
+            @Override
+            public void visitTree(JCTree tree) { /* no-op */ }
+
+            @Override
+            public void visitVarDef(JCVariableDecl tree) {
+                if ((tree.mods.flags & ENUM) != 0) {
+                    if (tree.init instanceof JCNewClass &&
+                        ((JCNewClass) tree.init).def != null) {
+                        specialized = true;
+                    }
+                }
+            }
+        }
+
+        SpecialTreeVisitor sts = new SpecialTreeVisitor();
+        JCClassDecl cdef = (JCClassDecl) tree;
+        for (JCTree defs: cdef.defs) {
+            defs.accept(sts);
+            if (sts.specialized) return 0;
+        }
+        return FINAL;
+    }
+
+/* *************************************************************************
+ * Type Validation
+ **************************************************************************/
+
+    /** Validate a type expression. That is,
+     *  check that all type arguments of a parametric type are within
+     *  their bounds. This must be done in a second phase after type attribution
+     *  since a class might have a subclass as type parameter bound. E.g:
+     *
+     *  <pre>{@code
+     *  class B<A extends C> { ... }
+     *  class C extends B<C> { ... }
+     *  }</pre>
+     *
+     *  and we can't make sure that the bound is already attributed because
+     *  of possible cycles.
+     *
+     * Visitor method: Validate a type expression, if it is not null, catching
+     *  and reporting any completion failures.
+     */
+    void validate(JCTree tree, Env<AttrContext> env) {
+        validate(tree, env, true);
+    }
+    void validate(JCTree tree, Env<AttrContext> env, boolean checkRaw) {
+        new Validator(env).validateTree(tree, checkRaw, true);
+    }
+
+    /** Visitor method: Validate a list of type expressions.
+     */
+    void validate(List<? extends JCTree> trees, Env<AttrContext> env) {
+        for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
+            validate(l.head, env);
+    }
+
+    /** A visitor class for type validation.
+     */
+    class Validator extends JCTree.Visitor {
+
+        boolean checkRaw;
+        boolean isOuter;
+        Env<AttrContext> env;
+
+        Validator(Env<AttrContext> env) {
+            this.env = env;
+        }
+
+        @Override
+        public void visitTypeArray(JCArrayTypeTree tree) {
+            validateTree(tree.elemtype, checkRaw, isOuter);
+        }
+
+        @Override
+        public void visitTypeApply(JCTypeApply tree) {
+            if (tree.type.hasTag(CLASS)) {
+                List<JCExpression> args = tree.arguments;
+                List<Type> forms = tree.type.tsym.type.getTypeArguments();
+
+                Type incompatibleArg = firstIncompatibleTypeArg(tree.type);
+                if (incompatibleArg != null) {
+                    for (JCTree arg : tree.arguments) {
+                        if (arg.type == incompatibleArg) {
+                            log.error(arg, Errors.NotWithinBounds(incompatibleArg, forms.head));
+                        }
+                        forms = forms.tail;
+                     }
+                 }
+
+                forms = tree.type.tsym.type.getTypeArguments();
+
+                boolean is_java_lang_Class = tree.type.tsym.flatName() == names.java_lang_Class;
+
+                // For matching pairs of actual argument types `a' and
+                // formal type parameters with declared bound `b' ...
+                while (args.nonEmpty() && forms.nonEmpty()) {
+                    validateTree(args.head,
+                            !(isOuter && is_java_lang_Class),
+                            false);
+                    args = args.tail;
+                    forms = forms.tail;
+                }
+
+                // Check that this type is either fully parameterized, or
+                // not parameterized at all.
+                if (tree.type.getEnclosingType().isRaw())
+                    log.error(tree.pos(), Errors.ImproperlyFormedTypeInnerRawParam);
+                if (tree.clazz.hasTag(SELECT))
+                    visitSelectInternal((JCFieldAccess)tree.clazz);
+            }
+        }
+
+        @Override
+        public void visitTypeParameter(JCTypeParameter tree) {
+            validateTrees(tree.bounds, true, isOuter);
+            checkClassBounds(tree.pos(), tree.type);
+        }
+
+        @Override
+        public void visitWildcard(JCWildcard tree) {
+            if (tree.inner != null)
+                validateTree(tree.inner, true, isOuter);
+        }
+
+        @Override
+        public void visitSelect(JCFieldAccess tree) {
+            if (tree.type.hasTag(CLASS)) {
+                visitSelectInternal(tree);
+
+                // Check that this type is either fully parameterized, or
+                // not parameterized at all.
+                if (tree.selected.type.isParameterized() && tree.type.tsym.type.getTypeArguments().nonEmpty())
+                    log.error(tree.pos(), Errors.ImproperlyFormedTypeParamMissing);
+            }
+        }
+
+        public void visitSelectInternal(JCFieldAccess tree) {
+            if (tree.type.tsym.isStatic() &&
+                tree.selected.type.isParameterized()) {
+                // The enclosing type is not a class, so we are
+                // looking at a static member type.  However, the
+                // qualifying expression is parameterized.
+                log.error(tree.pos(), Errors.CantSelectStaticClassFromParamType);
+            } else {
+                // otherwise validate the rest of the expression
+                tree.selected.accept(this);
+            }
+        }
+
+        @Override
+        public void visitAnnotatedType(JCAnnotatedType tree) {
+            tree.underlyingType.accept(this);
+        }
+
+        @Override
+        public void visitTypeIdent(JCPrimitiveTypeTree that) {
+            if (that.type.hasTag(TypeTag.VOID)) {
+                log.error(that.pos(), Errors.VoidNotAllowedHere);
+            }
+            super.visitTypeIdent(that);
+        }
+
+        /** Default visitor method: do nothing.
+         */
+        @Override
+        public void visitTree(JCTree tree) {
+        }
+
+        public void validateTree(JCTree tree, boolean checkRaw, boolean isOuter) {
+            if (tree != null) {
+                boolean prevCheckRaw = this.checkRaw;
+                this.checkRaw = checkRaw;
+                this.isOuter = isOuter;
+
+                try {
+                    tree.accept(this);
+                    if (checkRaw)
+                        checkRaw(tree, env);
+                } catch (CompletionFailure ex) {
+                    completionError(tree.pos(), ex);
+                } finally {
+                    this.checkRaw = prevCheckRaw;
+                }
+            }
+        }
+
+        public void validateTrees(List<? extends JCTree> trees, boolean checkRaw, boolean isOuter) {
+            for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
+                validateTree(l.head, checkRaw, isOuter);
+        }
+    }
+
+    void checkRaw(JCTree tree, Env<AttrContext> env) {
+        if (lint.isEnabled(LintCategory.RAW) &&
+            tree.type.hasTag(CLASS) &&
+            !TreeInfo.isDiamond(tree) &&
+            !withinAnonConstr(env) &&
+            tree.type.isRaw()) {
+            log.warning(LintCategory.RAW,
+                    tree.pos(), Warnings.RawClassUse(tree.type, tree.type.tsym.type));
+        }
+    }
+    //where
+        private boolean withinAnonConstr(Env<AttrContext> env) {
+            return env.enclClass.name.isEmpty() &&
+                    env.enclMethod != null && env.enclMethod.name == names.init;
+        }
+
+/* *************************************************************************
+ * Exception checking
+ **************************************************************************/
+
+    /* The following methods treat classes as sets that contain
+     * the class itself and all their subclasses
+     */
+
+    /** Is given type a subtype of some of the types in given list?
+     */
+    boolean subset(Type t, List<Type> ts) {
+        for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
+            if (types.isSubtype(t, l.head)) return true;
+        return false;
+    }
+
+    /** Is given type a subtype or supertype of
+     *  some of the types in given list?
+     */
+    boolean intersects(Type t, List<Type> ts) {
+        for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
+            if (types.isSubtype(t, l.head) || types.isSubtype(l.head, t)) return true;
+        return false;
+    }
+
+    /** Add type set to given type list, unless it is a subclass of some class
+     *  in the list.
+     */
+    List<Type> incl(Type t, List<Type> ts) {
+        return subset(t, ts) ? ts : excl(t, ts).prepend(t);
+    }
+
+    /** Remove type set from type set list.
+     */
+    List<Type> excl(Type t, List<Type> ts) {
+        if (ts.isEmpty()) {
+            return ts;
+        } else {
+            List<Type> ts1 = excl(t, ts.tail);
+            if (types.isSubtype(ts.head, t)) return ts1;
+            else if (ts1 == ts.tail) return ts;
+            else return ts1.prepend(ts.head);
+        }
+    }
+
+    /** Form the union of two type set lists.
+     */
+    List<Type> union(List<Type> ts1, List<Type> ts2) {
+        List<Type> ts = ts1;
+        for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
+            ts = incl(l.head, ts);
+        return ts;
+    }
+
+    /** Form the difference of two type lists.
+     */
+    List<Type> diff(List<Type> ts1, List<Type> ts2) {
+        List<Type> ts = ts1;
+        for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
+            ts = excl(l.head, ts);
+        return ts;
+    }
+
+    /** Form the intersection of two type lists.
+     */
+    public List<Type> intersect(List<Type> ts1, List<Type> ts2) {
+        List<Type> ts = List.nil();
+        for (List<Type> l = ts1; l.nonEmpty(); l = l.tail)
+            if (subset(l.head, ts2)) ts = incl(l.head, ts);
+        for (List<Type> l = ts2; l.nonEmpty(); l = l.tail)
+            if (subset(l.head, ts1)) ts = incl(l.head, ts);
+        return ts;
+    }
+
+    /** Is exc an exception symbol that need not be declared?
+     */
+    boolean isUnchecked(ClassSymbol exc) {
+        return
+            exc.kind == ERR ||
+            exc.isSubClass(syms.errorType.tsym, types) ||
+            exc.isSubClass(syms.runtimeExceptionType.tsym, types);
+    }
+
+    /** Is exc an exception type that need not be declared?
+     */
+    boolean isUnchecked(Type exc) {
+        return
+            (exc.hasTag(TYPEVAR)) ? isUnchecked(types.supertype(exc)) :
+            (exc.hasTag(CLASS)) ? isUnchecked((ClassSymbol)exc.tsym) :
+            exc.hasTag(BOT);
+    }
+
+    boolean isChecked(Type exc) {
+        return !isUnchecked(exc);
+    }
+
+    /** Same, but handling completion failures.
+     */
+    boolean isUnchecked(DiagnosticPosition pos, Type exc) {
+        try {
+            return isUnchecked(exc);
+        } catch (CompletionFailure ex) {
+            completionError(pos, ex);
+            return true;
+        }
+    }
+
+    /** Is exc handled by given exception list?
+     */
+    boolean isHandled(Type exc, List<Type> handled) {
+        return isUnchecked(exc) || subset(exc, handled);
+    }
+
+    /** Return all exceptions in thrown list that are not in handled list.
+     *  @param thrown     The list of thrown exceptions.
+     *  @param handled    The list of handled exceptions.
+     */
+    List<Type> unhandled(List<Type> thrown, List<Type> handled) {
+        List<Type> unhandled = List.nil();
+        for (List<Type> l = thrown; l.nonEmpty(); l = l.tail)
+            if (!isHandled(l.head, handled)) unhandled = unhandled.prepend(l.head);
+        return unhandled;
+    }
+
+/* *************************************************************************
+ * Overriding/Implementation checking
+ **************************************************************************/
+
+    /** The level of access protection given by a flag set,
+     *  where PRIVATE is highest and PUBLIC is lowest.
+     */
+    static int protection(long flags) {
+        switch ((short)(flags & AccessFlags)) {
+        case PRIVATE: return 3;
+        case PROTECTED: return 1;
+        default:
+        case PUBLIC: return 0;
+        case 0: return 2;
+        }
+    }
+
+    /** A customized "cannot override" error message.
+     *  @param m      The overriding method.
+     *  @param other  The overridden method.
+     *  @return       An internationalized string.
+     */
+    Fragment cannotOverride(MethodSymbol m, MethodSymbol other) {
+        Symbol mloc = m.location();
+        Symbol oloc = other.location();
+
+        if ((other.owner.flags() & INTERFACE) == 0)
+            return Fragments.CantOverride(m, mloc, other, oloc);
+        else if ((m.owner.flags() & INTERFACE) == 0)
+            return Fragments.CantImplement(m, mloc, other, oloc);
+        else
+            return Fragments.ClashesWith(m, mloc, other, oloc);
+    }
+
+    /** A customized "override" warning message.
+     *  @param m      The overriding method.
+     *  @param other  The overridden method.
+     *  @return       An internationalized string.
+     */
+    Fragment uncheckedOverrides(MethodSymbol m, MethodSymbol other) {
+        Symbol mloc = m.location();
+        Symbol oloc = other.location();
+
+        if ((other.owner.flags() & INTERFACE) == 0)
+            return Fragments.UncheckedOverride(m, mloc, other, oloc);
+        else if ((m.owner.flags() & INTERFACE) == 0)
+            return Fragments.UncheckedImplement(m, mloc, other, oloc);
+        else
+            return Fragments.UncheckedClashWith(m, mloc, other, oloc);
+    }
+
+    /** A customized "override" warning message.
+     *  @param m      The overriding method.
+     *  @param other  The overridden method.
+     *  @return       An internationalized string.
+     */
+    Fragment varargsOverrides(MethodSymbol m, MethodSymbol other) {
+        Symbol mloc = m.location();
+        Symbol oloc = other.location();
+
+        if ((other.owner.flags() & INTERFACE) == 0)
+            return Fragments.VarargsOverride(m, mloc, other, oloc);
+        else  if ((m.owner.flags() & INTERFACE) == 0)
+            return Fragments.VarargsImplement(m, mloc, other, oloc);
+        else
+            return Fragments.VarargsClashWith(m, mloc, other, oloc);
+    }
+
+    /** Check that this method conforms with overridden method 'other'.
+     *  where `origin' is the class where checking started.
+     *  Complications:
+     *  (1) Do not check overriding of synthetic methods
+     *      (reason: they might be final).
+     *      todo: check whether this is still necessary.
+     *  (2) Admit the case where an interface proxy throws fewer exceptions
+     *      than the method it implements. Augment the proxy methods with the
+     *      undeclared exceptions in this case.
+     *  (3) When generics are enabled, admit the case where an interface proxy
+     *      has a result type
+     *      extended by the result type of the method it implements.
+     *      Change the proxies result type to the smaller type in this case.
+     *
+     *  @param tree         The tree from which positions
+     *                      are extracted for errors.
+     *  @param m            The overriding method.
+     *  @param other        The overridden method.
+     *  @param origin       The class of which the overriding method
+     *                      is a member.
+     */
+    void checkOverride(JCTree tree,
+                       MethodSymbol m,
+                       MethodSymbol other,
+                       ClassSymbol origin) {
+        // Don't check overriding of synthetic methods or by bridge methods.
+        if ((m.flags() & (SYNTHETIC|BRIDGE)) != 0 || (other.flags() & SYNTHETIC) != 0) {
+            return;
+        }
+
+        // Error if static method overrides instance method (JLS 8.4.6.2).
+        if ((m.flags() & STATIC) != 0 &&
+                   (other.flags() & STATIC) == 0) {
+            log.error(TreeInfo.diagnosticPositionFor(m, tree),
+                      Errors.OverrideStatic(cannotOverride(m, other)));
+            m.flags_field |= BAD_OVERRIDE;
+            return;
+        }
+
+        // Error if instance method overrides static or final
+        // method (JLS 8.4.6.1).
+        if ((other.flags() & FINAL) != 0 ||
+                 (m.flags() & STATIC) == 0 &&
+                 (other.flags() & STATIC) != 0) {
+            log.error(TreeInfo.diagnosticPositionFor(m, tree),
+                      Errors.OverrideMeth(cannotOverride(m, other),
+                                          asFlagSet(other.flags() & (FINAL | STATIC))));
+            m.flags_field |= BAD_OVERRIDE;
+            return;
+        }
+
+        if ((m.owner.flags() & ANNOTATION) != 0) {
+            // handled in validateAnnotationMethod
+            return;
+        }
+
+        // Error if overriding method has weaker access (JLS 8.4.6.3).
+        if (protection(m.flags()) > protection(other.flags())) {
+            log.error(TreeInfo.diagnosticPositionFor(m, tree),
+                      (other.flags() & AccessFlags) == 0 ?
+                              Errors.OverrideWeakerAccess(cannotOverride(m, other),
+                                                          "package") :
+                              Errors.OverrideWeakerAccess(cannotOverride(m, other),
+                                                          asFlagSet(other.flags() & AccessFlags)));
+            m.flags_field |= BAD_OVERRIDE;
+            return;
+        }
+
+        Type mt = types.memberType(origin.type, m);
+        Type ot = types.memberType(origin.type, other);
+        // Error if overriding result type is different
+        // (or, in the case of generics mode, not a subtype) of
+        // overridden result type. We have to rename any type parameters
+        // before comparing types.
+        List<Type> mtvars = mt.getTypeArguments();
+        List<Type> otvars = ot.getTypeArguments();
+        Type mtres = mt.getReturnType();
+        Type otres = types.subst(ot.getReturnType(), otvars, mtvars);
+
+        overrideWarner.clear();
+        boolean resultTypesOK =
+            types.returnTypeSubstitutable(mt, ot, otres, overrideWarner);
+        if (!resultTypesOK) {
+            if ((m.flags() & STATIC) != 0 && (other.flags() & STATIC) != 0) {
+                log.error(TreeInfo.diagnosticPositionFor(m, tree),
+                          Errors.OverrideIncompatibleRet(Fragments.CantHide(m, m.location(), other,
+                                        other.location()), mtres, otres));
+                m.flags_field |= BAD_OVERRIDE;
+            } else {
+                log.error(TreeInfo.diagnosticPositionFor(m, tree),
+                          Errors.OverrideIncompatibleRet(cannotOverride(m, other), mtres, otres));
+                m.flags_field |= BAD_OVERRIDE;
+            }
+            return;
+        } else if (overrideWarner.hasNonSilentLint(LintCategory.UNCHECKED)) {
+            warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
+                    "override.unchecked.ret",
+                    uncheckedOverrides(m, other),
+                    mtres, otres);
+        }
+
+        // Error if overriding method throws an exception not reported
+        // by overridden method.
+        List<Type> otthrown = types.subst(ot.getThrownTypes(), otvars, mtvars);
+        List<Type> unhandledErased = unhandled(mt.getThrownTypes(), types.erasure(otthrown));
+        List<Type> unhandledUnerased = unhandled(mt.getThrownTypes(), otthrown);
+        if (unhandledErased.nonEmpty()) {
+            log.error(TreeInfo.diagnosticPositionFor(m, tree),
+                      Errors.OverrideMethDoesntThrow(cannotOverride(m, other), unhandledUnerased.head));
+            m.flags_field |= BAD_OVERRIDE;
+            return;
+        }
+        else if (unhandledUnerased.nonEmpty()) {
+            warnUnchecked(TreeInfo.diagnosticPositionFor(m, tree),
+                          "override.unchecked.thrown",
+                         cannotOverride(m, other),
+                         unhandledUnerased.head);
+            return;
+        }
+
+        // Optional warning if varargs don't agree
+        if ((((m.flags() ^ other.flags()) & Flags.VARARGS) != 0)
+            && lint.isEnabled(LintCategory.OVERRIDES)) {
+            log.warning(TreeInfo.diagnosticPositionFor(m, tree),
+                        ((m.flags() & Flags.VARARGS) != 0)
+                        ? Warnings.OverrideVarargsMissing(varargsOverrides(m, other))
+                        : Warnings.OverrideVarargsExtra(varargsOverrides(m, other)));
+        }
+
+        // Warn if instance method overrides bridge method (compiler spec ??)
+        if ((other.flags() & BRIDGE) != 0) {
+            log.warning(TreeInfo.diagnosticPositionFor(m, tree),
+                        Warnings.OverrideBridge(uncheckedOverrides(m, other)));
+        }
+
+        // Warn if a deprecated method overridden by a non-deprecated one.
+        if (!isDeprecatedOverrideIgnorable(other, origin)) {
+            Lint prevLint = setLint(lint.augment(m));
+            try {
+                checkDeprecated(TreeInfo.diagnosticPositionFor(m, tree), m, other);
+            } finally {
+                setLint(prevLint);
+            }
+        }
+    }
+    // where
+        private boolean isDeprecatedOverrideIgnorable(MethodSymbol m, ClassSymbol origin) {
+            // If the method, m, is defined in an interface, then ignore the issue if the method
+            // is only inherited via a supertype and also implemented in the supertype,
+            // because in that case, we will rediscover the issue when examining the method
+            // in the supertype.
+            // If the method, m, is not defined in an interface, then the only time we need to
+            // address the issue is when the method is the supertype implemementation: any other
+            // case, we will have dealt with when examining the supertype classes
+            ClassSymbol mc = m.enclClass();
+            Type st = types.supertype(origin.type);
+            if (!st.hasTag(CLASS))
+                return true;
+            MethodSymbol stimpl = m.implementation((ClassSymbol)st.tsym, types, false);
+
+            if (mc != null && ((mc.flags() & INTERFACE) != 0)) {
+                List<Type> intfs = types.interfaces(origin.type);
+                return (intfs.contains(mc.type) ? false : (stimpl != null));
+            }
+            else
+                return (stimpl != m);
+        }
+
+
+    // used to check if there were any unchecked conversions
+    Warner overrideWarner = new Warner();
+
+    /** Check that a class does not inherit two concrete methods
+     *  with the same signature.
+     *  @param pos          Position to be used for error reporting.
+     *  @param site         The class type to be checked.
+     */
+    public void checkCompatibleConcretes(DiagnosticPosition pos, Type site) {
+        Type sup = types.supertype(site);
+        if (!sup.hasTag(CLASS)) return;
+
+        for (Type t1 = sup;
+             t1.hasTag(CLASS) && t1.tsym.type.isParameterized();
+             t1 = types.supertype(t1)) {
+            for (Symbol s1 : t1.tsym.members().getSymbols(NON_RECURSIVE)) {
+                if (s1.kind != MTH ||
+                    (s1.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
+                    !s1.isInheritedIn(site.tsym, types) ||
+                    ((MethodSymbol)s1).implementation(site.tsym,
+                                                      types,
+                                                      true) != s1)
+                    continue;
+                Type st1 = types.memberType(t1, s1);
+                int s1ArgsLength = st1.getParameterTypes().length();
+                if (st1 == s1.type) continue;
+
+                for (Type t2 = sup;
+                     t2.hasTag(CLASS);
+                     t2 = types.supertype(t2)) {
+                    for (Symbol s2 : t2.tsym.members().getSymbolsByName(s1.name)) {
+                        if (s2 == s1 ||
+                            s2.kind != MTH ||
+                            (s2.flags() & (STATIC|SYNTHETIC|BRIDGE)) != 0 ||
+                            s2.type.getParameterTypes().length() != s1ArgsLength ||
+                            !s2.isInheritedIn(site.tsym, types) ||
+                            ((MethodSymbol)s2).implementation(site.tsym,
+                                                              types,
+                                                              true) != s2)
+                            continue;
+                        Type st2 = types.memberType(t2, s2);
+                        if (types.overrideEquivalent(st1, st2))
+                            log.error(pos,
+                                      Errors.ConcreteInheritanceConflict(s1, t1, s2, t2, sup));
+                    }
+                }
+            }
+        }
+    }
+
+    /** Check that classes (or interfaces) do not each define an abstract
+     *  method with same name and arguments but incompatible return types.
+     *  @param pos          Position to be used for error reporting.
+     *  @param t1           The first argument type.
+     *  @param t2           The second argument type.
+     */
+    public boolean checkCompatibleAbstracts(DiagnosticPosition pos,
+                                            Type t1,
+                                            Type t2,
+                                            Type site) {
+        if ((site.tsym.flags() & COMPOUND) != 0) {
+            // special case for intersections: need to eliminate wildcards in supertypes
+            t1 = types.capture(t1);
+            t2 = types.capture(t2);
+        }
+        return firstIncompatibility(pos, t1, t2, site) == null;
+    }
+
+    /** Return the first method which is defined with same args
+     *  but different return types in two given interfaces, or null if none
+     *  exists.
+     *  @param t1     The first type.
+     *  @param t2     The second type.
+     *  @param site   The most derived type.
+     *  @returns symbol from t2 that conflicts with one in t1.
+     */
+    private Symbol firstIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
+        Map<TypeSymbol,Type> interfaces1 = new HashMap<>();
+        closure(t1, interfaces1);
+        Map<TypeSymbol,Type> interfaces2;
+        if (t1 == t2)
+            interfaces2 = interfaces1;
+        else
+            closure(t2, interfaces1, interfaces2 = new HashMap<>());
+
+        for (Type t3 : interfaces1.values()) {
+            for (Type t4 : interfaces2.values()) {
+                Symbol s = firstDirectIncompatibility(pos, t3, t4, site);
+                if (s != null) return s;
+            }
+        }
+        return null;
+    }
+
+    /** Compute all the supertypes of t, indexed by type symbol. */
+    private void closure(Type t, Map<TypeSymbol,Type> typeMap) {
+        if (!t.hasTag(CLASS)) return;
+        if (typeMap.put(t.tsym, t) == null) {
+            closure(types.supertype(t), typeMap);
+            for (Type i : types.interfaces(t))
+                closure(i, typeMap);
+        }
+    }
+
+    /** Compute all the supertypes of t, indexed by type symbol (except thise in typesSkip). */
+    private void closure(Type t, Map<TypeSymbol,Type> typesSkip, Map<TypeSymbol,Type> typeMap) {
+        if (!t.hasTag(CLASS)) return;
+        if (typesSkip.get(t.tsym) != null) return;
+        if (typeMap.put(t.tsym, t) == null) {
+            closure(types.supertype(t), typesSkip, typeMap);
+            for (Type i : types.interfaces(t))
+                closure(i, typesSkip, typeMap);
+        }
+    }
+
+    /** Return the first method in t2 that conflicts with a method from t1. */
+    private Symbol firstDirectIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
+        for (Symbol s1 : t1.tsym.members().getSymbols(NON_RECURSIVE)) {
+            Type st1 = null;
+            if (s1.kind != MTH || !s1.isInheritedIn(site.tsym, types) ||
+                    (s1.flags() & SYNTHETIC) != 0) continue;
+            Symbol impl = ((MethodSymbol)s1).implementation(site.tsym, types, false);
+            if (impl != null && (impl.flags() & ABSTRACT) == 0) continue;
+            for (Symbol s2 : t2.tsym.members().getSymbolsByName(s1.name)) {
+                if (s1 == s2) continue;
+                if (s2.kind != MTH || !s2.isInheritedIn(site.tsym, types) ||
+                        (s2.flags() & SYNTHETIC) != 0) continue;
+                if (st1 == null) st1 = types.memberType(t1, s1);
+                Type st2 = types.memberType(t2, s2);
+                if (types.overrideEquivalent(st1, st2)) {
+                    List<Type> tvars1 = st1.getTypeArguments();
+                    List<Type> tvars2 = st2.getTypeArguments();
+                    Type rt1 = st1.getReturnType();
+                    Type rt2 = types.subst(st2.getReturnType(), tvars2, tvars1);
+                    boolean compat =
+                        types.isSameType(rt1, rt2) ||
+                        !rt1.isPrimitiveOrVoid() &&
+                        !rt2.isPrimitiveOrVoid() &&
+                        (types.covariantReturnType(rt1, rt2, types.noWarnings) ||
+                         types.covariantReturnType(rt2, rt1, types.noWarnings)) ||
+                         checkCommonOverriderIn(s1,s2,site);
+                    if (!compat) {
+                        log.error(pos, Errors.TypesIncompatibleDiffRet(t1, t2, s2.name +
+                                "(" + types.memberType(t2, s2).getParameterTypes() + ")"));
+                        return s2;
+                    }
+                } else if (checkNameClash((ClassSymbol)site.tsym, s1, s2) &&
+                        !checkCommonOverriderIn(s1, s2, site)) {
+                    log.error(pos, Errors.NameClashSameErasureNoOverride(
+                            s1.name, types.memberType(site, s1).asMethodType().getParameterTypes(), s1.location(),
+                            s2.name, types.memberType(site, s2).asMethodType().getParameterTypes(), s2.location()));
+                    return s2;
+                }
+            }
+        }
+        return null;
+    }
+    //WHERE
+    boolean checkCommonOverriderIn(Symbol s1, Symbol s2, Type site) {
+        Map<TypeSymbol,Type> supertypes = new HashMap<>();
+        Type st1 = types.memberType(site, s1);
+        Type st2 = types.memberType(site, s2);
+        closure(site, supertypes);
+        for (Type t : supertypes.values()) {
+            for (Symbol s3 : t.tsym.members().getSymbolsByName(s1.name)) {
+                if (s3 == s1 || s3 == s2 || s3.kind != MTH || (s3.flags() & (BRIDGE|SYNTHETIC)) != 0) continue;
+                Type st3 = types.memberType(site,s3);
+                if (types.overrideEquivalent(st3, st1) &&
+                        types.overrideEquivalent(st3, st2) &&
+                        types.returnTypeSubstitutable(st3, st1) &&
+                        types.returnTypeSubstitutable(st3, st2)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    /** Check that a given method conforms with any method it overrides.
+     *  @param tree         The tree from which positions are extracted
+     *                      for errors.
+     *  @param m            The overriding method.
+     */
+    void checkOverride(Env<AttrContext> env, JCMethodDecl tree, MethodSymbol m) {
+        ClassSymbol origin = (ClassSymbol)m.owner;
+        if ((origin.flags() & ENUM) != 0 && names.finalize.equals(m.name))
+            if (m.overrides(syms.enumFinalFinalize, origin, types, false)) {
+                log.error(tree.pos(), Errors.EnumNoFinalize);
+                return;
+            }
+        for (Type t = origin.type; t.hasTag(CLASS);
+             t = types.supertype(t)) {
+            if (t != origin.type) {
+                checkOverride(tree, t, origin, m);
+            }
+            for (Type t2 : types.interfaces(t)) {
+                checkOverride(tree, t2, origin, m);
+            }
+        }
+
+        final boolean explicitOverride = m.attribute(syms.overrideType.tsym) != null;
+        // Check if this method must override a super method due to being annotated with @Override
+        // or by virtue of being a member of a diamond inferred anonymous class. Latter case is to
+        // be treated "as if as they were annotated" with @Override.
+        boolean mustOverride = explicitOverride ||
+                (env.info.isAnonymousDiamond && !m.isConstructor() && !m.isPrivate());
+        if (mustOverride && !isOverrider(m)) {
+            DiagnosticPosition pos = tree.pos();
+            for (JCAnnotation a : tree.getModifiers().annotations) {
+                if (a.annotationType.type.tsym == syms.overrideType.tsym) {
+                    pos = a.pos();
+                    break;
+                }
+            }
+            log.error(pos,
+                      explicitOverride ? (m.isStatic() ? Errors.StaticMethodsCannotBeAnnotatedWithOverride : Errors.MethodDoesNotOverrideSuperclass) :
+                                Errors.AnonymousDiamondMethodDoesNotOverrideSuperclass(Fragments.DiamondAnonymousMethodsImplicitlyOverride));
+        }
+    }
+
+    void checkOverride(JCTree tree, Type site, ClassSymbol origin, MethodSymbol m) {
+        TypeSymbol c = site.tsym;
+        for (Symbol sym : c.members().getSymbolsByName(m.name)) {
+            if (m.overrides(sym, origin, types, false)) {
+                if ((sym.flags() & ABSTRACT) == 0) {
+                    checkOverride(tree, m, (MethodSymbol)sym, origin);
+                }
+            }
+        }
+    }
+
+    private Filter<Symbol> equalsHasCodeFilter = s -> MethodSymbol.implementation_filter.accepts(s) &&
+            (s.flags() & BAD_OVERRIDE) == 0;
+
+    public void checkClassOverrideEqualsAndHashIfNeeded(DiagnosticPosition pos,
+            ClassSymbol someClass) {
+        /* At present, annotations cannot possibly have a method that is override
+         * equivalent with Object.equals(Object) but in any case the condition is
+         * fine for completeness.
+         */
+        if (someClass == (ClassSymbol)syms.objectType.tsym ||
+            someClass.isInterface() || someClass.isEnum() ||
+            (someClass.flags() & ANNOTATION) != 0 ||
+            (someClass.flags() & ABSTRACT) != 0) return;
+        //anonymous inner classes implementing interfaces need especial treatment
+        if (someClass.isAnonymous()) {
+            List<Type> interfaces =  types.interfaces(someClass.type);
+            if (interfaces != null && !interfaces.isEmpty() &&
+                interfaces.head.tsym == syms.comparatorType.tsym) return;
+        }
+        checkClassOverrideEqualsAndHash(pos, someClass);
+    }
+
+    private void checkClassOverrideEqualsAndHash(DiagnosticPosition pos,
+            ClassSymbol someClass) {
+        if (lint.isEnabled(LintCategory.OVERRIDES)) {
+            MethodSymbol equalsAtObject = (MethodSymbol)syms.objectType
+                    .tsym.members().findFirst(names.equals);
+            MethodSymbol hashCodeAtObject = (MethodSymbol)syms.objectType
+                    .tsym.members().findFirst(names.hashCode);
+            boolean overridesEquals = types.implementation(equalsAtObject,
+                someClass, false, equalsHasCodeFilter).owner == someClass;
+            boolean overridesHashCode = types.implementation(hashCodeAtObject,
+                someClass, false, equalsHasCodeFilter) != hashCodeAtObject;
+
+            if (overridesEquals && !overridesHashCode) {
+                log.warning(LintCategory.OVERRIDES, pos,
+                            Warnings.OverrideEqualsButNotHashcode(someClass));
+            }
+        }
+    }
+
+    public void checkModuleName (JCModuleDecl tree) {
+        Name moduleName = tree.sym.name;
+        Assert.checkNonNull(moduleName);
+        if (lint.isEnabled(LintCategory.MODULE)) {
+            JCExpression qualId = tree.qualId;
+            while (qualId != null) {
+                Name componentName;
+                DiagnosticPosition pos;
+                switch (qualId.getTag()) {
+                    case SELECT:
+                        JCFieldAccess selectNode = ((JCFieldAccess) qualId);
+                        componentName = selectNode.name;
+                        pos = selectNode.pos();
+                        qualId = selectNode.selected;
+                        break;
+                    case IDENT:
+                        componentName = ((JCIdent) qualId).name;
+                        pos = qualId.pos();
+                        qualId = null;
+                        break;
+                    default:
+                        throw new AssertionError("Unexpected qualified identifier: " + qualId.toString());
+                }
+                if (componentName != null) {
+                    String moduleNameComponentString = componentName.toString();
+                    int nameLength = moduleNameComponentString.length();
+                    if (nameLength > 0 && Character.isDigit(moduleNameComponentString.charAt(nameLength - 1))) {
+                        log.warning(Lint.LintCategory.MODULE, pos, Warnings.PoorChoiceForModuleName(componentName));
+                    }
+                }
+            }
+        }
+    }
+
+    private boolean checkNameClash(ClassSymbol origin, Symbol s1, Symbol s2) {
+        ClashFilter cf = new ClashFilter(origin.type);
+        return (cf.accepts(s1) &&
+                cf.accepts(s2) &&
+                types.hasSameArgs(s1.erasure(types), s2.erasure(types)));
+    }
+
+
+    /** Check that all abstract members of given class have definitions.
+     *  @param pos          Position to be used for error reporting.
+     *  @param c            The class.
+     */
+    void checkAllDefined(DiagnosticPosition pos, ClassSymbol c) {
+        MethodSymbol undef = types.firstUnimplementedAbstract(c);
+        if (undef != null) {
+            MethodSymbol undef1 =
+                new MethodSymbol(undef.flags(), undef.name,
+                                 types.memberType(c.type, undef), undef.owner);
+            log.error(pos,
+                      Errors.DoesNotOverrideAbstract(c, undef1, undef1.location()));
+        }
+    }
+
+    void checkNonCyclicDecl(JCClassDecl tree) {
+        CycleChecker cc = new CycleChecker();
+        cc.scan(tree);
+        if (!cc.errorFound && !cc.partialCheck) {
+            tree.sym.flags_field |= ACYCLIC;
+        }
+    }
+
+    class CycleChecker extends TreeScanner {
+
+        List<Symbol> seenClasses = List.nil();
+        boolean errorFound = false;
+        boolean partialCheck = false;
+
+        private void checkSymbol(DiagnosticPosition pos, Symbol sym) {
+            if (sym != null && sym.kind == TYP) {
+                Env<AttrContext> classEnv = enter.getEnv((TypeSymbol)sym);
+                if (classEnv != null) {
+                    DiagnosticSource prevSource = log.currentSource();
+                    try {
+                        log.useSource(classEnv.toplevel.sourcefile);
+                        scan(classEnv.tree);
+                    }
+                    finally {
+                        log.useSource(prevSource.getFile());
+                    }
+                } else if (sym.kind == TYP) {
+                    checkClass(pos, sym, List.nil());
+                }
+            } else {
+                //not completed yet
+                partialCheck = true;
+            }
+        }
+
+        @Override
+        public void visitSelect(JCFieldAccess tree) {
+            super.visitSelect(tree);
+            checkSymbol(tree.pos(), tree.sym);
+        }
+
+        @Override
+        public void visitIdent(JCIdent tree) {
+            checkSymbol(tree.pos(), tree.sym);
+        }
+
+        @Override
+        public void visitTypeApply(JCTypeApply tree) {
+            scan(tree.clazz);
+        }
+
+        @Override
+        public void visitTypeArray(JCArrayTypeTree tree) {
+            scan(tree.elemtype);
+        }
+
+        @Override
+        public void visitClassDef(JCClassDecl tree) {
+            List<JCTree> supertypes = List.nil();
+            if (tree.getExtendsClause() != null) {
+                supertypes = supertypes.prepend(tree.getExtendsClause());
+            }
+            if (tree.getImplementsClause() != null) {
+                for (JCTree intf : tree.getImplementsClause()) {
+                    supertypes = supertypes.prepend(intf);
+                }
+            }
+            checkClass(tree.pos(), tree.sym, supertypes);
+        }
+
+        void checkClass(DiagnosticPosition pos, Symbol c, List<JCTree> supertypes) {
+            if ((c.flags_field & ACYCLIC) != 0)
+                return;
+            if (seenClasses.contains(c)) {
+                errorFound = true;
+                noteCyclic(pos, (ClassSymbol)c);
+            } else if (!c.type.isErroneous()) {
+                try {
+                    seenClasses = seenClasses.prepend(c);
+                    if (c.type.hasTag(CLASS)) {
+                        if (supertypes.nonEmpty()) {
+                            scan(supertypes);
+                        }
+                        else {
+                            ClassType ct = (ClassType)c.type;
+                            if (ct.supertype_field == null ||
+                                    ct.interfaces_field == null) {
+                                //not completed yet
+                                partialCheck = true;
+                                return;
+                            }
+                            checkSymbol(pos, ct.supertype_field.tsym);
+                            for (Type intf : ct.interfaces_field) {
+                                checkSymbol(pos, intf.tsym);
+                            }
+                        }
+                        if (c.owner.kind == TYP) {
+                            checkSymbol(pos, c.owner);
+                        }
+                    }
+                } finally {
+                    seenClasses = seenClasses.tail;
+                }
+            }
+        }
+    }
+
+    /** Check for cyclic references. Issue an error if the
+     *  symbol of the type referred to has a LOCKED flag set.
+     *
+     *  @param pos      Position to be used for error reporting.
+     *  @param t        The type referred to.
+     */
+    void checkNonCyclic(DiagnosticPosition pos, Type t) {
+        checkNonCyclicInternal(pos, t);
+    }
+
+
+    void checkNonCyclic(DiagnosticPosition pos, TypeVar t) {
+        checkNonCyclic1(pos, t, List.nil());
+    }
+
+    private void checkNonCyclic1(DiagnosticPosition pos, Type t, List<TypeVar> seen) {
+        final TypeVar tv;
+        if  (t.hasTag(TYPEVAR) && (t.tsym.flags() & UNATTRIBUTED) != 0)
+            return;
+        if (seen.contains(t)) {
+            tv = (TypeVar)t;
+            tv.bound = types.createErrorType(t);
+            log.error(pos, Errors.CyclicInheritance(t));
+        } else if (t.hasTag(TYPEVAR)) {
+            tv = (TypeVar)t;
+            seen = seen.prepend(tv);
+            for (Type b : types.getBounds(tv))
+                checkNonCyclic1(pos, b, seen);
+        }
+    }
+
+    /** Check for cyclic references. Issue an error if the
+     *  symbol of the type referred to has a LOCKED flag set.
+     *
+     *  @param pos      Position to be used for error reporting.
+     *  @param t        The type referred to.
+     *  @returns        True if the check completed on all attributed classes
+     */
+    private boolean checkNonCyclicInternal(DiagnosticPosition pos, Type t) {
+        boolean complete = true; // was the check complete?
+        //- System.err.println("checkNonCyclicInternal("+t+");");//DEBUG
+        Symbol c = t.tsym;
+        if ((c.flags_field & ACYCLIC) != 0) return true;
+
+        if ((c.flags_field & LOCKED) != 0) {
+            noteCyclic(pos, (ClassSymbol)c);
+        } else if (!c.type.isErroneous()) {
+            try {
+                c.flags_field |= LOCKED;
+                if (c.type.hasTag(CLASS)) {
+                    ClassType clazz = (ClassType)c.type;
+                    if (clazz.interfaces_field != null)
+                        for (List<Type> l=clazz.interfaces_field; l.nonEmpty(); l=l.tail)
+                            complete &= checkNonCyclicInternal(pos, l.head);
+                    if (clazz.supertype_field != null) {
+                        Type st = clazz.supertype_field;
+                        if (st != null && st.hasTag(CLASS))
+                            complete &= checkNonCyclicInternal(pos, st);
+                    }
+                    if (c.owner.kind == TYP)
+                        complete &= checkNonCyclicInternal(pos, c.owner.type);
+                }
+            } finally {
+                c.flags_field &= ~LOCKED;
+            }
+        }
+        if (complete)
+            complete = ((c.flags_field & UNATTRIBUTED) == 0) && c.isCompleted();
+        if (complete) c.flags_field |= ACYCLIC;
+        return complete;
+    }
+
+    /** Note that we found an inheritance cycle. */
+    private void noteCyclic(DiagnosticPosition pos, ClassSymbol c) {
+        log.error(pos, Errors.CyclicInheritance(c));
+        for (List<Type> l=types.interfaces(c.type); l.nonEmpty(); l=l.tail)
+            l.head = types.createErrorType((ClassSymbol)l.head.tsym, Type.noType);
+        Type st = types.supertype(c.type);
+        if (st.hasTag(CLASS))
+            ((ClassType)c.type).supertype_field = types.createErrorType((ClassSymbol)st.tsym, Type.noType);
+        c.type = types.createErrorType(c, c.type);
+        c.flags_field |= ACYCLIC;
+    }
+
+    /** Check that all methods which implement some
+     *  method conform to the method they implement.
+     *  @param tree         The class definition whose members are checked.
+     */
+    void checkImplementations(JCClassDecl tree) {
+        checkImplementations(tree, tree.sym, tree.sym);
+    }
+    //where
+        /** Check that all methods which implement some
+         *  method in `ic' conform to the method they implement.
+         */
+        void checkImplementations(JCTree tree, ClassSymbol origin, ClassSymbol ic) {
+            for (List<Type> l = types.closure(ic.type); l.nonEmpty(); l = l.tail) {
+                ClassSymbol lc = (ClassSymbol)l.head.tsym;
+                if ((lc.flags() & ABSTRACT) != 0) {
+                    for (Symbol sym : lc.members().getSymbols(NON_RECURSIVE)) {
+                        if (sym.kind == MTH &&
+                            (sym.flags() & (STATIC|ABSTRACT)) == ABSTRACT) {
+                            MethodSymbol absmeth = (MethodSymbol)sym;
+                            MethodSymbol implmeth = absmeth.implementation(origin, types, false);
+                            if (implmeth != null && implmeth != absmeth &&
+                                (implmeth.owner.flags() & INTERFACE) ==
+                                (origin.flags() & INTERFACE)) {
+                                // don't check if implmeth is in a class, yet
+                                // origin is an interface. This case arises only
+                                // if implmeth is declared in Object. The reason is
+                                // that interfaces really don't inherit from
+                                // Object it's just that the compiler represents
+                                // things that way.
+                                checkOverride(tree, implmeth, absmeth, origin);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+    /** Check that all abstract methods implemented by a class are
+     *  mutually compatible.
+     *  @param pos          Position to be used for error reporting.
+     *  @param c            The class whose interfaces are checked.
+     */
+    void checkCompatibleSupertypes(DiagnosticPosition pos, Type c) {
+        List<Type> supertypes = types.interfaces(c);
+        Type supertype = types.supertype(c);
+        if (supertype.hasTag(CLASS) &&
+            (supertype.tsym.flags() & ABSTRACT) != 0)
+            supertypes = supertypes.prepend(supertype);
+        for (List<Type> l = supertypes; l.nonEmpty(); l = l.tail) {
+            if (!l.head.getTypeArguments().isEmpty() &&
+                !checkCompatibleAbstracts(pos, l.head, l.head, c))
+                return;
+            for (List<Type> m = supertypes; m != l; m = m.tail)
+                if (!checkCompatibleAbstracts(pos, l.head, m.head, c))
+                    return;
+        }
+        checkCompatibleConcretes(pos, c);
+    }
+
+    void checkConflicts(DiagnosticPosition pos, Symbol sym, TypeSymbol c) {
+        for (Type ct = c.type; ct != Type.noType ; ct = types.supertype(ct)) {
+            for (Symbol sym2 : ct.tsym.members().getSymbolsByName(sym.name, NON_RECURSIVE)) {
+                // VM allows methods and variables with differing types
+                if (sym.kind == sym2.kind &&
+                    types.isSameType(types.erasure(sym.type), types.erasure(sym2.type)) &&
+                    sym != sym2 &&
+                    (sym.flags() & Flags.SYNTHETIC) != (sym2.flags() & Flags.SYNTHETIC) &&
+                    (sym.flags() & BRIDGE) == 0 && (sym2.flags() & BRIDGE) == 0) {
+                    syntheticError(pos, (sym2.flags() & SYNTHETIC) == 0 ? sym2 : sym);
+                    return;
+                }
+            }
+        }
+    }
+
+    /** Check that all non-override equivalent methods accessible from 'site'
+     *  are mutually compatible (JLS 8.4.8/9.4.1).
+     *
+     *  @param pos  Position to be used for error reporting.
+     *  @param site The class whose methods are checked.
+     *  @param sym  The method symbol to be checked.
+     */
+    void checkOverrideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
+         ClashFilter cf = new ClashFilter(site);
+        //for each method m1 that is overridden (directly or indirectly)
+        //by method 'sym' in 'site'...
+
+        List<MethodSymbol> potentiallyAmbiguousList = List.nil();
+        boolean overridesAny = false;
+        for (Symbol m1 : types.membersClosure(site, false).getSymbolsByName(sym.name, cf)) {
+            if (!sym.overrides(m1, site.tsym, types, false)) {
+                if (m1 == sym) {
+                    continue;
+                }
+
+                if (!overridesAny) {
+                    potentiallyAmbiguousList = potentiallyAmbiguousList.prepend((MethodSymbol)m1);
+                }
+                continue;
+            }
+
+            if (m1 != sym) {
+                overridesAny = true;
+                potentiallyAmbiguousList = List.nil();
+            }
+
+            //...check each method m2 that is a member of 'site'
+            for (Symbol m2 : types.membersClosure(site, false).getSymbolsByName(sym.name, cf)) {
+                if (m2 == m1) continue;
+                //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
+                //a member of 'site') and (ii) m1 has the same erasure as m2, issue an error
+                if (!types.isSubSignature(sym.type, types.memberType(site, m2), allowStrictMethodClashCheck) &&
+                        types.hasSameArgs(m2.erasure(types), m1.erasure(types))) {
+                    sym.flags_field |= CLASH;
+                    if (m1 == sym) {
+                        log.error(pos, Errors.NameClashSameErasureNoOverride(
+                            m1.name, types.memberType(site, m1).asMethodType().getParameterTypes(), m1.location(),
+                            m2.name, types.memberType(site, m2).asMethodType().getParameterTypes(), m2.location()));
+                    } else {
+                        ClassType ct = (ClassType)site;
+                        String kind = ct.isInterface() ? "interface" : "class";
+                        log.error(pos, Errors.NameClashSameErasureNoOverride1(
+                            kind,
+                            ct.tsym.name,
+                            m1.name,
+                            types.memberType(site, m1).asMethodType().getParameterTypes(),
+                            m1.location(),
+                            m2.name,
+                            types.memberType(site, m2).asMethodType().getParameterTypes(),
+                            m2.location()));
+                    }
+                    return;
+                }
+            }
+        }
+
+        if (!overridesAny) {
+            for (MethodSymbol m: potentiallyAmbiguousList) {
+                checkPotentiallyAmbiguousOverloads(pos, site, sym, m);
+            }
+        }
+    }
+
+    /** Check that all static methods accessible from 'site' are
+     *  mutually compatible (JLS 8.4.8).
+     *
+     *  @param pos  Position to be used for error reporting.
+     *  @param site The class whose methods are checked.
+     *  @param sym  The method symbol to be checked.
+     */
+    void checkHideClashes(DiagnosticPosition pos, Type site, MethodSymbol sym) {
+        ClashFilter cf = new ClashFilter(site);
+        //for each method m1 that is a member of 'site'...
+        for (Symbol s : types.membersClosure(site, true).getSymbolsByName(sym.name, cf)) {
+            //if (i) the signature of 'sym' is not a subsignature of m1 (seen as
+            //a member of 'site') and (ii) 'sym' has the same erasure as m1, issue an error
+            if (!types.isSubSignature(sym.type, types.memberType(site, s), allowStrictMethodClashCheck)) {
+                if (types.hasSameArgs(s.erasure(types), sym.erasure(types))) {
+                    log.error(pos,
+                              Errors.NameClashSameErasureNoHide(sym, sym.location(), s, s.location()));
+                    return;
+                } else {
+                    checkPotentiallyAmbiguousOverloads(pos, site, sym, (MethodSymbol)s);
+                }
+            }
+         }
+     }
+
+     //where
+     private class ClashFilter implements Filter<Symbol> {
+
+         Type site;
+
+         ClashFilter(Type site) {
+             this.site = site;
+         }
+
+         boolean shouldSkip(Symbol s) {
+             return (s.flags() & CLASH) != 0 &&
+                s.owner == site.tsym;
+         }
+
+         public boolean accepts(Symbol s) {
+             return s.kind == MTH &&
+                     (s.flags() & SYNTHETIC) == 0 &&
+                     !shouldSkip(s) &&
+                     s.isInheritedIn(site.tsym, types) &&
+                     !s.isConstructor();
+         }
+     }
+
+    void checkDefaultMethodClashes(DiagnosticPosition pos, Type site) {
+        DefaultMethodClashFilter dcf = new DefaultMethodClashFilter(site);
+        for (Symbol m : types.membersClosure(site, false).getSymbols(dcf)) {
+            Assert.check(m.kind == MTH);
+            List<MethodSymbol> prov = types.interfaceCandidates(site, (MethodSymbol)m);
+            if (prov.size() > 1) {
+                ListBuffer<Symbol> abstracts = new ListBuffer<>();
+                ListBuffer<Symbol> defaults = new ListBuffer<>();
+                for (MethodSymbol provSym : prov) {
+                    if ((provSym.flags() & DEFAULT) != 0) {
+                        defaults = defaults.append(provSym);
+                    } else if ((provSym.flags() & ABSTRACT) != 0) {
+                        abstracts = abstracts.append(provSym);
+                    }
+                    if (defaults.nonEmpty() && defaults.size() + abstracts.size() >= 2) {
+                        //strong semantics - issue an error if two sibling interfaces
+                        //have two override-equivalent defaults - or if one is abstract
+                        //and the other is default
+                        String errKey;
+                        Symbol s1 = defaults.first();
+                        Symbol s2;
+                        if (defaults.size() > 1) {
+                            errKey = "types.incompatible.unrelated.defaults";
+                            s2 = defaults.toList().tail.head;
+                        } else {
+                            errKey = "types.incompatible.abstract.default";
+                            s2 = abstracts.first();
+                        }
+                        log.error(pos, errKey,
+                                Kinds.kindName(site.tsym), site,
+                                m.name, types.memberType(site, m).getParameterTypes(),
+                                s1.location(), s2.location());
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    //where
+     private class DefaultMethodClashFilter implements Filter<Symbol> {
+
+         Type site;
+
+         DefaultMethodClashFilter(Type site) {
+             this.site = site;
+         }
+
+         public boolean accepts(Symbol s) {
+             return s.kind == MTH &&
+                     (s.flags() & DEFAULT) != 0 &&
+                     s.isInheritedIn(site.tsym, types) &&
+                     !s.isConstructor();
+         }
+     }
+
+    /**
+      * Report warnings for potentially ambiguous method declarations. Two declarations
+      * are potentially ambiguous if they feature two unrelated functional interface
+      * in same argument position (in which case, a call site passing an implicit
+      * lambda would be ambiguous).
+      */
+    void checkPotentiallyAmbiguousOverloads(DiagnosticPosition pos, Type site,
+            MethodSymbol msym1, MethodSymbol msym2) {
+        if (msym1 != msym2 &&
+                allowDefaultMethods &&
+                lint.isEnabled(LintCategory.OVERLOADS) &&
+                (msym1.flags() & POTENTIALLY_AMBIGUOUS) == 0 &&
+                (msym2.flags() & POTENTIALLY_AMBIGUOUS) == 0) {
+            Type mt1 = types.memberType(site, msym1);
+            Type mt2 = types.memberType(site, msym2);
+            //if both generic methods, adjust type variables
+            if (mt1.hasTag(FORALL) && mt2.hasTag(FORALL) &&
+                    types.hasSameBounds((ForAll)mt1, (ForAll)mt2)) {
+                mt2 = types.subst(mt2, ((ForAll)mt2).tvars, ((ForAll)mt1).tvars);
+            }
+            //expand varargs methods if needed
+            int maxLength = Math.max(mt1.getParameterTypes().length(), mt2.getParameterTypes().length());
+            List<Type> args1 = rs.adjustArgs(mt1.getParameterTypes(), msym1, maxLength, true);
+            List<Type> args2 = rs.adjustArgs(mt2.getParameterTypes(), msym2, maxLength, true);
+            //if arities don't match, exit
+            if (args1.length() != args2.length()) return;
+            boolean potentiallyAmbiguous = false;
+            while (args1.nonEmpty() && args2.nonEmpty()) {
+                Type s = args1.head;
+                Type t = args2.head;
+                if (!types.isSubtype(t, s) && !types.isSubtype(s, t)) {
+                    if (types.isFunctionalInterface(s) && types.isFunctionalInterface(t) &&
+                            types.findDescriptorType(s).getParameterTypes().length() > 0 &&
+                            types.findDescriptorType(s).getParameterTypes().length() ==
+                            types.findDescriptorType(t).getParameterTypes().length()) {
+                        potentiallyAmbiguous = true;
+                    } else {
+                        break;
+                    }
+                }
+                args1 = args1.tail;
+                args2 = args2.tail;
+            }
+            if (potentiallyAmbiguous) {
+                //we found two incompatible functional interfaces with same arity
+                //this means a call site passing an implicit lambda would be ambigiuous
+                msym1.flags_field |= POTENTIALLY_AMBIGUOUS;
+                msym2.flags_field |= POTENTIALLY_AMBIGUOUS;
+                log.warning(LintCategory.OVERLOADS, pos,
+                            Warnings.PotentiallyAmbiguousOverload(msym1, msym1.location(),
+                                                                  msym2, msym2.location()));
+                return;
+            }
+        }
+    }
+
+    void checkAccessFromSerializableElement(final JCTree tree, boolean isLambda) {
+        if (warnOnAnyAccessToMembers ||
+            (lint.isEnabled(LintCategory.SERIAL) &&
+            !lint.isSuppressed(LintCategory.SERIAL) &&
+            isLambda)) {
+            Symbol sym = TreeInfo.symbol(tree);
+            if (!sym.kind.matches(KindSelector.VAL_MTH)) {
+                return;
+            }
+
+            if (sym.kind == VAR) {
+                if ((sym.flags() & PARAMETER) != 0 ||
+                    sym.isLocal() ||
+                    sym.name == names._this ||
+                    sym.name == names._super) {
+                    return;
+                }
+            }
+
+            if (!types.isSubtype(sym.owner.type, syms.serializableType) &&
+                isEffectivelyNonPublic(sym)) {
+                if (isLambda) {
+                    if (belongsToRestrictedPackage(sym)) {
+                        log.warning(LintCategory.SERIAL, tree.pos(),
+                                    Warnings.AccessToMemberFromSerializableLambda(sym));
+                    }
+                } else {
+                    log.warning(tree.pos(),
+                                Warnings.AccessToMemberFromSerializableElement(sym));
+                }
+            }
+        }
+    }
+
+    private boolean isEffectivelyNonPublic(Symbol sym) {
+        if (sym.packge() == syms.rootPackage) {
+            return false;
+        }
+
+        while (sym.kind != PCK) {
+            if ((sym.flags() & PUBLIC) == 0) {
+                return true;
+            }
+            sym = sym.owner;
+        }
+        return false;
+    }
+
+    private boolean belongsToRestrictedPackage(Symbol sym) {
+        String fullName = sym.packge().fullname.toString();
+        return fullName.startsWith("java.") ||
+                fullName.startsWith("javax.") ||
+                fullName.startsWith("sun.") ||
+                fullName.contains(".internal.");
+    }
+
+    /** Report a conflict between a user symbol and a synthetic symbol.
+     */
+    private void syntheticError(DiagnosticPosition pos, Symbol sym) {
+        if (!sym.type.isErroneous()) {
+            log.error(pos, Errors.SyntheticNameConflict(sym, sym.location()));
+        }
+    }
+
+    /** Check that class c does not implement directly or indirectly
+     *  the same parameterized interface with two different argument lists.
+     *  @param pos          Position to be used for error reporting.
+     *  @param type         The type whose interfaces are checked.
+     */
+    void checkClassBounds(DiagnosticPosition pos, Type type) {
+        checkClassBounds(pos, new HashMap<TypeSymbol,Type>(), type);
+    }
+//where
+        /** Enter all interfaces of type `type' into the hash table `seensofar'
+         *  with their class symbol as key and their type as value. Make
+         *  sure no class is entered with two different types.
+         */
+        void checkClassBounds(DiagnosticPosition pos,
+                              Map<TypeSymbol,Type> seensofar,
+                              Type type) {
+            if (type.isErroneous()) return;
+            for (List<Type> l = types.interfaces(type); l.nonEmpty(); l = l.tail) {
+                Type it = l.head;
+                Type oldit = seensofar.put(it.tsym, it);
+                if (oldit != null) {
+                    List<Type> oldparams = oldit.allparams();
+                    List<Type> newparams = it.allparams();
+                    if (!types.containsTypeEquivalent(oldparams, newparams))
+                        log.error(pos,
+                                  Errors.CantInheritDiffArg(it.tsym,
+                                                            Type.toString(oldparams),
+                                                            Type.toString(newparams)));
+                }
+                checkClassBounds(pos, seensofar, it);
+            }
+            Type st = types.supertype(type);
+            if (st != Type.noType) checkClassBounds(pos, seensofar, st);
+        }
+
+    /** Enter interface into into set.
+     *  If it existed already, issue a "repeated interface" error.
+     */
+    void checkNotRepeated(DiagnosticPosition pos, Type it, Set<Type> its) {
+        if (its.contains(it))
+            log.error(pos, Errors.RepeatedInterface);
+        else {
+            its.add(it);
+        }
+    }
+
+/* *************************************************************************
+ * Check annotations
+ **************************************************************************/
+
+    /**
+     * Recursively validate annotations values
+     */
+    void validateAnnotationTree(JCTree tree) {
+        class AnnotationValidator extends TreeScanner {
+            @Override
+            public void visitAnnotation(JCAnnotation tree) {
+                if (!tree.type.isErroneous()) {
+                    super.visitAnnotation(tree);
+                    validateAnnotation(tree);
+                }
+            }
+        }
+        tree.accept(new AnnotationValidator());
+    }
+
+    /**
+     *  {@literal
+     *  Annotation types are restricted to primitives, String, an
+     *  enum, an annotation, Class, Class<?>, Class<? extends
+     *  Anything>, arrays of the preceding.
+     *  }
+     */
+    void validateAnnotationType(JCTree restype) {
+        // restype may be null if an error occurred, so don't bother validating it
+        if (restype != null) {
+            validateAnnotationType(restype.pos(), restype.type);
+        }
+    }
+
+    void validateAnnotationType(DiagnosticPosition pos, Type type) {
+        if (type.isPrimitive()) return;
+        if (types.isSameType(type, syms.stringType)) return;
+        if ((type.tsym.flags() & Flags.ENUM) != 0) return;
+        if ((type.tsym.flags() & Flags.ANNOTATION) != 0) return;
+        if (types.cvarLowerBound(type).tsym == syms.classType.tsym) return;
+        if (types.isArray(type) && !types.isArray(types.elemtype(type))) {
+            validateAnnotationType(pos, types.elemtype(type));
+            return;
+        }
+        log.error(pos, Errors.InvalidAnnotationMemberType);
+    }
+
+    /**
+     * "It is also a compile-time error if any method declared in an
+     * annotation type has a signature that is override-equivalent to
+     * that of any public or protected method declared in class Object
+     * or in the interface annotation.Annotation."
+     *
+     * @jls 9.6 Annotation Types
+     */
+    void validateAnnotationMethod(DiagnosticPosition pos, MethodSymbol m) {
+        for (Type sup = syms.annotationType; sup.hasTag(CLASS); sup = types.supertype(sup)) {
+            Scope s = sup.tsym.members();
+            for (Symbol sym : s.getSymbolsByName(m.name)) {
+                if (sym.kind == MTH &&
+                    (sym.flags() & (PUBLIC | PROTECTED)) != 0 &&
+                    types.overrideEquivalent(m.type, sym.type))
+                    log.error(pos, Errors.IntfAnnotationMemberClash(sym, sup));
+            }
+        }
+    }
+
+    /** Check the annotations of a symbol.
+     */
+    public void validateAnnotations(List<JCAnnotation> annotations, Symbol s) {
+        for (JCAnnotation a : annotations)
+            validateAnnotation(a, s);
+    }
+
+    /** Check the type annotations.
+     */
+    public void validateTypeAnnotations(List<JCAnnotation> annotations, boolean isTypeParameter) {
+        for (JCAnnotation a : annotations)
+            validateTypeAnnotation(a, isTypeParameter);
+    }
+
+    /** Check an annotation of a symbol.
+     */
+    private void validateAnnotation(JCAnnotation a, Symbol s) {
+        validateAnnotationTree(a);
+
+        if (a.type.tsym.isAnnotationType() && !annotationApplicable(a, s))
+            log.error(a.pos(), Errors.AnnotationTypeNotApplicable);
+
+        if (a.annotationType.type.tsym == syms.functionalInterfaceType.tsym) {
+            if (s.kind != TYP) {
+                log.error(a.pos(), Errors.BadFunctionalIntfAnno);
+            } else if (!s.isInterface() || (s.flags() & ANNOTATION) != 0) {
+                log.error(a.pos(), Errors.BadFunctionalIntfAnno1(Fragments.NotAFunctionalIntf(s)));
+            }
+        }
+    }
+
+    public void validateTypeAnnotation(JCAnnotation a, boolean isTypeParameter) {
+        Assert.checkNonNull(a.type);
+        validateAnnotationTree(a);
+
+        if (a.hasTag(TYPE_ANNOTATION) &&
+                !a.annotationType.type.isErroneous() &&
+                !isTypeAnnotation(a, isTypeParameter)) {
+            log.error(a.pos(), Errors.AnnotationTypeNotApplicableToType(a.type));
+        }
+    }
+
+    /**
+     * Validate the proposed container 'repeatable' on the
+     * annotation type symbol 's'. Report errors at position
+     * 'pos'.
+     *
+     * @param s The (annotation)type declaration annotated with a @Repeatable
+     * @param repeatable the @Repeatable on 's'
+     * @param pos where to report errors
+     */
+    public void validateRepeatable(TypeSymbol s, Attribute.Compound repeatable, DiagnosticPosition pos) {
+        Assert.check(types.isSameType(repeatable.type, syms.repeatableType));
+
+        Type t = null;
+        List<Pair<MethodSymbol,Attribute>> l = repeatable.values;
+        if (!l.isEmpty()) {
+            Assert.check(l.head.fst.name == names.value);
+            t = ((Attribute.Class)l.head.snd).getValue();
+        }
+
+        if (t == null) {
+            // errors should already have been reported during Annotate
+            return;
+        }
+
+        validateValue(t.tsym, s, pos);
+        validateRetention(t.tsym, s, pos);
+        validateDocumented(t.tsym, s, pos);
+        validateInherited(t.tsym, s, pos);
+        validateTarget(t.tsym, s, pos);
+        validateDefault(t.tsym, pos);
+    }
+
+    private void validateValue(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
+        Symbol sym = container.members().findFirst(names.value);
+        if (sym != null && sym.kind == MTH) {
+            MethodSymbol m = (MethodSymbol) sym;
+            Type ret = m.getReturnType();
+            if (!(ret.hasTag(ARRAY) && types.isSameType(((ArrayType)ret).elemtype, contained.type))) {
+                log.error(pos,
+                          Errors.InvalidRepeatableAnnotationValueReturn(container,
+                                                                        ret,
+                                                                        types.makeArrayType(contained.type)));
+            }
+        } else {
+            log.error(pos, Errors.InvalidRepeatableAnnotationNoValue(container));
+        }
+    }
+
+    private void validateRetention(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
+        Attribute.RetentionPolicy containerRetention = types.getRetention(container);
+        Attribute.RetentionPolicy containedRetention = types.getRetention(contained);
+
+        boolean error = false;
+        switch (containedRetention) {
+        case RUNTIME:
+            if (containerRetention != Attribute.RetentionPolicy.RUNTIME) {
+                error = true;
+            }
+            break;
+        case CLASS:
+            if (containerRetention == Attribute.RetentionPolicy.SOURCE)  {
+                error = true;
+            }
+        }
+        if (error ) {
+            log.error(pos,
+                      Errors.InvalidRepeatableAnnotationRetention(container,
+                                                                  containerRetention.name(),
+                                                                  contained,
+                                                                  containedRetention.name()));
+        }
+    }
+
+    private void validateDocumented(Symbol container, Symbol contained, DiagnosticPosition pos) {
+        if (contained.attribute(syms.documentedType.tsym) != null) {
+            if (container.attribute(syms.documentedType.tsym) == null) {
+                log.error(pos, Errors.InvalidRepeatableAnnotationNotDocumented(container, contained));
+            }
+        }
+    }
+
+    private void validateInherited(Symbol container, Symbol contained, DiagnosticPosition pos) {
+        if (contained.attribute(syms.inheritedType.tsym) != null) {
+            if (container.attribute(syms.inheritedType.tsym) == null) {
+                log.error(pos, Errors.InvalidRepeatableAnnotationNotInherited(container, contained));
+            }
+        }
+    }
+
+    private void validateTarget(TypeSymbol container, TypeSymbol contained, DiagnosticPosition pos) {
+        // The set of targets the container is applicable to must be a subset
+        // (with respect to annotation target semantics) of the set of targets
+        // the contained is applicable to. The target sets may be implicit or
+        // explicit.
+
+        Set<Name> containerTargets;
+        Attribute.Array containerTarget = getAttributeTargetAttribute(container);
+        if (containerTarget == null) {
+            containerTargets = getDefaultTargetSet();
+        } else {
+            containerTargets = new HashSet<>();
+            for (Attribute app : containerTarget.values) {
+                if (!(app instanceof Attribute.Enum)) {
+                    continue; // recovery
+                }
+                Attribute.Enum e = (Attribute.Enum)app;
+                containerTargets.add(e.value.name);
+            }
+        }
+
+        Set<Name> containedTargets;
+        Attribute.Array containedTarget = getAttributeTargetAttribute(contained);
+        if (containedTarget == null) {
+            containedTargets = getDefaultTargetSet();
+        } else {
+            containedTargets = new HashSet<>();
+            for (Attribute app : containedTarget.values) {
+                if (!(app instanceof Attribute.Enum)) {
+                    continue; // recovery
+                }
+                Attribute.Enum e = (Attribute.Enum)app;
+                containedTargets.add(e.value.name);
+            }
+        }
+
+        if (!isTargetSubsetOf(containerTargets, containedTargets)) {
+            log.error(pos, Errors.InvalidRepeatableAnnotationIncompatibleTarget(container, contained));
+        }
+    }
+
+    /* get a set of names for the default target */
+    private Set<Name> getDefaultTargetSet() {
+        if (defaultTargets == null) {
+            Set<Name> targets = new HashSet<>();
+            targets.add(names.ANNOTATION_TYPE);
+            targets.add(names.CONSTRUCTOR);
+            targets.add(names.FIELD);
+            targets.add(names.LOCAL_VARIABLE);
+            targets.add(names.METHOD);
+            targets.add(names.PACKAGE);
+            targets.add(names.PARAMETER);
+            targets.add(names.TYPE);
+
+            defaultTargets = java.util.Collections.unmodifiableSet(targets);
+        }
+
+        return defaultTargets;
+    }
+    private Set<Name> defaultTargets;
+
+
+    /** Checks that s is a subset of t, with respect to ElementType
+     * semantics, specifically {ANNOTATION_TYPE} is a subset of {TYPE},
+     * and {TYPE_USE} covers the set {ANNOTATION_TYPE, TYPE, TYPE_USE,
+     * TYPE_PARAMETER}.
+     */
+    private boolean isTargetSubsetOf(Set<Name> s, Set<Name> t) {
+        // Check that all elements in s are present in t
+        for (Name n2 : s) {
+            boolean currentElementOk = false;
+            for (Name n1 : t) {
+                if (n1 == n2) {
+                    currentElementOk = true;
+                    break;
+                } else if (n1 == names.TYPE && n2 == names.ANNOTATION_TYPE) {
+                    currentElementOk = true;
+                    break;
+                } else if (n1 == names.TYPE_USE &&
+                        (n2 == names.TYPE ||
+                         n2 == names.ANNOTATION_TYPE ||
+                         n2 == names.TYPE_PARAMETER)) {
+                    currentElementOk = true;
+                    break;
+                }
+            }
+            if (!currentElementOk)
+                return false;
+        }
+        return true;
+    }
+
+    private void validateDefault(Symbol container, DiagnosticPosition pos) {
+        // validate that all other elements of containing type has defaults
+        Scope scope = container.members();
+        for(Symbol elm : scope.getSymbols()) {
+            if (elm.name != names.value &&
+                elm.kind == MTH &&
+                ((MethodSymbol)elm).defaultValue == null) {
+                log.error(pos,
+                          Errors.InvalidRepeatableAnnotationElemNondefault(container, elm));
+            }
+        }
+    }
+
+    /** Is s a method symbol that overrides a method in a superclass? */
+    boolean isOverrider(Symbol s) {
+        if (s.kind != MTH || s.isStatic())
+            return false;
+        MethodSymbol m = (MethodSymbol)s;
+        TypeSymbol owner = (TypeSymbol)m.owner;
+        for (Type sup : types.closure(owner.type)) {
+            if (sup == owner.type)
+                continue; // skip "this"
+            Scope scope = sup.tsym.members();
+            for (Symbol sym : scope.getSymbolsByName(m.name)) {
+                if (!sym.isStatic() && m.overrides(sym, owner, types, true))
+                    return true;
+            }
+        }
+        return false;
+    }
+
+    /** Is the annotation applicable to types? */
+    protected boolean isTypeAnnotation(JCAnnotation a, boolean isTypeParameter) {
+        List<Attribute> targets = typeAnnotations.annotationTargets(a.annotationType.type.tsym);
+        return (targets == null) ?
+                false :
+                targets.stream()
+                        .anyMatch(attr -> isTypeAnnotation(attr, isTypeParameter));
+    }
+    //where
+        boolean isTypeAnnotation(Attribute a, boolean isTypeParameter) {
+            Attribute.Enum e = (Attribute.Enum)a;
+            return (e.value.name == names.TYPE_USE ||
+                    (isTypeParameter && e.value.name == names.TYPE_PARAMETER));
+        }
+
+    /** Is the annotation applicable to the symbol? */
+    boolean annotationApplicable(JCAnnotation a, Symbol s) {
+        Attribute.Array arr = getAttributeTargetAttribute(a.annotationType.type.tsym);
+        Name[] targets;
+
+        if (arr == null) {
+            targets = defaultTargetMetaInfo(a, s);
+        } else {
+            // TODO: can we optimize this?
+            targets = new Name[arr.values.length];
+            for (int i=0; i<arr.values.length; ++i) {
+                Attribute app = arr.values[i];
+                if (!(app instanceof Attribute.Enum)) {
+                    return true; // recovery
+                }
+                Attribute.Enum e = (Attribute.Enum) app;
+                targets[i] = e.value.name;
+            }
+        }
+        for (Name target : targets) {
+            if (target == names.TYPE) {
+                if (s.kind == TYP)
+                    return true;
+            } else if (target == names.FIELD) {
+                if (s.kind == VAR && s.owner.kind != MTH)
+                    return true;
+            } else if (target == names.METHOD) {
+                if (s.kind == MTH && !s.isConstructor())
+                    return true;
+            } else if (target == names.PARAMETER) {
+                if (s.kind == VAR && s.owner.kind == MTH &&
+                      (s.flags() & PARAMETER) != 0) {
+                    return true;
+                }
+            } else if (target == names.CONSTRUCTOR) {
+                if (s.kind == MTH && s.isConstructor())
+                    return true;
+            } else if (target == names.LOCAL_VARIABLE) {
+                if (s.kind == VAR && s.owner.kind == MTH &&
+                      (s.flags() & PARAMETER) == 0) {
+                    return true;
+                }
+            } else if (target == names.ANNOTATION_TYPE) {
+                if (s.kind == TYP && (s.flags() & ANNOTATION) != 0) {
+                    return true;
+                }
+            } else if (target == names.PACKAGE) {
+                if (s.kind == PCK)
+                    return true;
+            } else if (target == names.TYPE_USE) {
+                if (s.kind == TYP || s.kind == VAR ||
+                        (s.kind == MTH && !s.isConstructor() &&
+                                !s.type.getReturnType().hasTag(VOID)) ||
+                        (s.kind == MTH && s.isConstructor())) {
+                    return true;
+                }
+            } else if (target == names.TYPE_PARAMETER) {
+                if (s.kind == TYP && s.type.hasTag(TYPEVAR))
+                    return true;
+            } else
+                return true; // Unknown ElementType. This should be an error at declaration site,
+                             // assume applicable.
+        }
+        return false;
+    }
+
+
+    Attribute.Array getAttributeTargetAttribute(TypeSymbol s) {
+        Attribute.Compound atTarget = s.getAnnotationTypeMetadata().getTarget();
+        if (atTarget == null) return null; // ok, is applicable
+        Attribute atValue = atTarget.member(names.value);
+        if (!(atValue instanceof Attribute.Array)) return null; // error recovery
+        return (Attribute.Array) atValue;
+    }
+
+    private final Name[] dfltTargetMeta;
+    private Name[] defaultTargetMetaInfo(JCAnnotation a, Symbol s) {
+        return dfltTargetMeta;
+    }
+
+    /** Check an annotation value.
+     *
+     * @param a The annotation tree to check
+     * @return true if this annotation tree is valid, otherwise false
+     */
+    public boolean validateAnnotationDeferErrors(JCAnnotation a) {
+        boolean res = false;
+        final Log.DiagnosticHandler diagHandler = new Log.DiscardDiagnosticHandler(log);
+        try {
+            res = validateAnnotation(a);
+        } finally {
+            log.popDiagnosticHandler(diagHandler);
+        }
+        return res;
+    }
+
+    private boolean validateAnnotation(JCAnnotation a) {
+        boolean isValid = true;
+        AnnotationTypeMetadata metadata = a.annotationType.type.tsym.getAnnotationTypeMetadata();
+
+        // collect an inventory of the annotation elements
+        Set<MethodSymbol> elements = metadata.getAnnotationElements();
+
+        // remove the ones that are assigned values
+        for (JCTree arg : a.args) {
+            if (!arg.hasTag(ASSIGN)) continue; // recovery
+            JCAssign assign = (JCAssign)arg;
+            Symbol m = TreeInfo.symbol(assign.lhs);
+            if (m == null || m.type.isErroneous()) continue;
+            if (!elements.remove(m)) {
+                isValid = false;
+                log.error(assign.lhs.pos(),
+                          Errors.DuplicateAnnotationMemberValue(m.name, a.type));
+            }
+        }
+
+        // all the remaining ones better have default values
+        List<Name> missingDefaults = List.nil();
+        Set<MethodSymbol> membersWithDefault = metadata.getAnnotationElementsWithDefault();
+        for (MethodSymbol m : elements) {
+            if (m.type.isErroneous())
+                continue;
+
+            if (!membersWithDefault.contains(m))
+                missingDefaults = missingDefaults.append(m.name);
+        }
+        missingDefaults = missingDefaults.reverse();
+        if (missingDefaults.nonEmpty()) {
+            isValid = false;
+            String key = (missingDefaults.size() > 1)
+                    ? "annotation.missing.default.value.1"
+                    : "annotation.missing.default.value";
+            log.error(a.pos(), key, a.type, missingDefaults);
+        }
+
+        return isValid && validateTargetAnnotationValue(a);
+    }
+
+    /* Validate the special java.lang.annotation.Target annotation */
+    boolean validateTargetAnnotationValue(JCAnnotation a) {
+        // special case: java.lang.annotation.Target must not have
+        // repeated values in its value member
+        if (a.annotationType.type.tsym != syms.annotationTargetType.tsym ||
+                a.args.tail == null)
+            return true;
+
+        boolean isValid = true;
+        if (!a.args.head.hasTag(ASSIGN)) return false; // error recovery
+        JCAssign assign = (JCAssign) a.args.head;
+        Symbol m = TreeInfo.symbol(assign.lhs);
+        if (m.name != names.value) return false;
+        JCTree rhs = assign.rhs;
+        if (!rhs.hasTag(NEWARRAY)) return false;
+        JCNewArray na = (JCNewArray) rhs;
+        Set<Symbol> targets = new HashSet<>();
+        for (JCTree elem : na.elems) {
+            if (!targets.add(TreeInfo.symbol(elem))) {
+                isValid = false;
+                log.error(elem.pos(), Errors.RepeatedAnnotationTarget);
+            }
+        }
+        return isValid;
+    }
+
+    void checkDeprecatedAnnotation(DiagnosticPosition pos, Symbol s) {
+        if (lint.isEnabled(LintCategory.DEP_ANN) && s.isDeprecatableViaAnnotation() &&
+            (s.flags() & DEPRECATED) != 0 &&
+            !syms.deprecatedType.isErroneous() &&
+            s.attribute(syms.deprecatedType.tsym) == null) {
+            log.warning(LintCategory.DEP_ANN,
+                    pos, Warnings.MissingDeprecatedAnnotation);
+        }
+        // Note: @Deprecated has no effect on local variables, parameters and package decls.
+        if (lint.isEnabled(LintCategory.DEPRECATION) && !s.isDeprecatableViaAnnotation()) {
+            if (!syms.deprecatedType.isErroneous() && s.attribute(syms.deprecatedType.tsym) != null) {
+                log.warning(LintCategory.DEPRECATION, pos,
+                            Warnings.DeprecatedAnnotationHasNoEffect(Kinds.kindName(s)));
+            }
+        }
+    }
+
+    void checkDeprecated(final DiagnosticPosition pos, final Symbol other, final Symbol s) {
+        if ( (s.isDeprecatedForRemoval()
+                || s.isDeprecated() && !other.isDeprecated())
+                && (s.outermostClass() != other.outermostClass() || s.outermostClass() == null)) {
+            deferredLintHandler.report(() -> warnDeprecated(pos, s));
+        }
+    }
+
+    void checkSunAPI(final DiagnosticPosition pos, final Symbol s) {
+        if ((s.flags() & PROPRIETARY) != 0) {
+            deferredLintHandler.report(() -> {
+                log.mandatoryWarning(pos, Warnings.SunProprietary(s));
+            });
+        }
+    }
+
+    void checkProfile(final DiagnosticPosition pos, final Symbol s) {
+        if (profile != Profile.DEFAULT && (s.flags() & NOT_IN_PROFILE) != 0) {
+            log.error(pos, Errors.NotInProfile(s, profile));
+        }
+    }
+
+/* *************************************************************************
+ * Check for recursive annotation elements.
+ **************************************************************************/
+
+    /** Check for cycles in the graph of annotation elements.
+     */
+    void checkNonCyclicElements(JCClassDecl tree) {
+        if ((tree.sym.flags_field & ANNOTATION) == 0) return;
+        Assert.check((tree.sym.flags_field & LOCKED) == 0);
+        try {
+            tree.sym.flags_field |= LOCKED;
+            for (JCTree def : tree.defs) {
+                if (!def.hasTag(METHODDEF)) continue;
+                JCMethodDecl meth = (JCMethodDecl)def;
+                checkAnnotationResType(meth.pos(), meth.restype.type);
+            }
+        } finally {
+            tree.sym.flags_field &= ~LOCKED;
+            tree.sym.flags_field |= ACYCLIC_ANN;
+        }
+    }
+
+    void checkNonCyclicElementsInternal(DiagnosticPosition pos, TypeSymbol tsym) {
+        if ((tsym.flags_field & ACYCLIC_ANN) != 0)
+            return;
+        if ((tsym.flags_field & LOCKED) != 0) {
+            log.error(pos, Errors.CyclicAnnotationElement(tsym));
+            return;
+        }
+        try {
+            tsym.flags_field |= LOCKED;
+            for (Symbol s : tsym.members().getSymbols(NON_RECURSIVE)) {
+                if (s.kind != MTH)
+                    continue;
+                checkAnnotationResType(pos, ((MethodSymbol)s).type.getReturnType());
+            }
+        } finally {
+            tsym.flags_field &= ~LOCKED;
+            tsym.flags_field |= ACYCLIC_ANN;
+        }
+    }
+
+    void checkAnnotationResType(DiagnosticPosition pos, Type type) {
+        switch (type.getTag()) {
+        case CLASS:
+            if ((type.tsym.flags() & ANNOTATION) != 0)
+                checkNonCyclicElementsInternal(pos, type.tsym);
+            break;
+        case ARRAY:
+            checkAnnotationResType(pos, types.elemtype(type));
+            break;
+        default:
+            break; // int etc
+        }
+    }
+
+/* *************************************************************************
+ * Check for cycles in the constructor call graph.
+ **************************************************************************/
+
+    /** Check for cycles in the graph of constructors calling other
+     *  constructors.
+     */
+    void checkCyclicConstructors(JCClassDecl tree) {
+        Map<Symbol,Symbol> callMap = new HashMap<>();
+
+        // enter each constructor this-call into the map
+        for (List<JCTree> l = tree.defs; l.nonEmpty(); l = l.tail) {
+            JCMethodInvocation app = TreeInfo.firstConstructorCall(l.head);
+            if (app == null) continue;
+            JCMethodDecl meth = (JCMethodDecl) l.head;
+            if (TreeInfo.name(app.meth) == names._this) {
+                callMap.put(meth.sym, TreeInfo.symbol(app.meth));
+            } else {
+                meth.sym.flags_field |= ACYCLIC;
+            }
+        }
+
+        // Check for cycles in the map
+        Symbol[] ctors = new Symbol[0];
+        ctors = callMap.keySet().toArray(ctors);
+        for (Symbol caller : ctors) {
+            checkCyclicConstructor(tree, caller, callMap);
+        }
+    }
+
+    /** Look in the map to see if the given constructor is part of a
+     *  call cycle.
+     */
+    private void checkCyclicConstructor(JCClassDecl tree, Symbol ctor,
+                                        Map<Symbol,Symbol> callMap) {
+        if (ctor != null && (ctor.flags_field & ACYCLIC) == 0) {
+            if ((ctor.flags_field & LOCKED) != 0) {
+                log.error(TreeInfo.diagnosticPositionFor(ctor, tree),
+                          Errors.RecursiveCtorInvocation);
+            } else {
+                ctor.flags_field |= LOCKED;
+                checkCyclicConstructor(tree, callMap.remove(ctor), callMap);
+                ctor.flags_field &= ~LOCKED;
+            }
+            ctor.flags_field |= ACYCLIC;
+        }
+    }
+
+/* *************************************************************************
+ * Miscellaneous
+ **************************************************************************/
+
+    /**
+     *  Check for division by integer constant zero
+     *  @param pos           Position for error reporting.
+     *  @param operator      The operator for the expression
+     *  @param operand       The right hand operand for the expression
+     */
+    void checkDivZero(final DiagnosticPosition pos, Symbol operator, Type operand) {
+        if (operand.constValue() != null
+            && operand.getTag().isSubRangeOf(LONG)
+            && ((Number) (operand.constValue())).longValue() == 0) {
+            int opc = ((OperatorSymbol)operator).opcode;
+            if (opc == ByteCodes.idiv || opc == ByteCodes.imod
+                || opc == ByteCodes.ldiv || opc == ByteCodes.lmod) {
+                deferredLintHandler.report(() -> warnDivZero(pos));
+            }
+        }
+    }
+
+    /**
+     * Check for empty statements after if
+     */
+    void checkEmptyIf(JCIf tree) {
+        if (tree.thenpart.hasTag(SKIP) && tree.elsepart == null &&
+                lint.isEnabled(LintCategory.EMPTY))
+            log.warning(LintCategory.EMPTY, tree.thenpart.pos(), Warnings.EmptyIf);
+    }
+
+    /** Check that symbol is unique in given scope.
+     *  @param pos           Position for error reporting.
+     *  @param sym           The symbol.
+     *  @param s             The scope.
+     */
+    boolean checkUnique(DiagnosticPosition pos, Symbol sym, Scope s) {
+        if (sym.type.isErroneous())
+            return true;
+        if (sym.owner.name == names.any) return false;
+        for (Symbol byName : s.getSymbolsByName(sym.name, NON_RECURSIVE)) {
+            if (sym != byName &&
+                    (byName.flags() & CLASH) == 0 &&
+                    sym.kind == byName.kind &&
+                    sym.name != names.error &&
+                    (sym.kind != MTH ||
+                     types.hasSameArgs(sym.type, byName.type) ||
+                     types.hasSameArgs(types.erasure(sym.type), types.erasure(byName.type)))) {
+                if ((sym.flags() & VARARGS) != (byName.flags() & VARARGS)) {
+                    varargsDuplicateError(pos, sym, byName);
+                    return true;
+                } else if (sym.kind == MTH && !types.hasSameArgs(sym.type, byName.type, false)) {
+                    duplicateErasureError(pos, sym, byName);
+                    sym.flags_field |= CLASH;
+                    return true;
+                } else {
+                    duplicateError(pos, byName);
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    /** Report duplicate declaration error.
+     */
+    void duplicateErasureError(DiagnosticPosition pos, Symbol sym1, Symbol sym2) {
+        if (!sym1.type.isErroneous() && !sym2.type.isErroneous()) {
+            log.error(pos, Errors.NameClashSameErasure(sym1, sym2));
+        }
+    }
+
+    /**Check that types imported through the ordinary imports don't clash with types imported
+     * by other (static or ordinary) imports. Note that two static imports may import two clashing
+     * types without an error on the imports.
+     * @param toplevel       The toplevel tree for which the test should be performed.
+     */
+    void checkImportsUnique(JCCompilationUnit toplevel) {
+        WriteableScope ordinallyImportedSoFar = WriteableScope.create(toplevel.packge);
+        WriteableScope staticallyImportedSoFar = WriteableScope.create(toplevel.packge);
+        WriteableScope topLevelScope = toplevel.toplevelScope;
+
+        for (JCTree def : toplevel.defs) {
+            if (!def.hasTag(IMPORT))
+                continue;
+
+            JCImport imp = (JCImport) def;
+
+            if (imp.importScope == null)
+                continue;
+
+            for (Symbol sym : imp.importScope.getSymbols(sym -> sym.kind == TYP)) {
+                if (imp.isStatic()) {
+                    checkUniqueImport(imp.pos(), ordinallyImportedSoFar, staticallyImportedSoFar, topLevelScope, sym, true);
+                    staticallyImportedSoFar.enter(sym);
+                } else {
+                    checkUniqueImport(imp.pos(), ordinallyImportedSoFar, staticallyImportedSoFar, topLevelScope, sym, false);
+                    ordinallyImportedSoFar.enter(sym);
+                }
+            }
+
+            imp.importScope = null;
+        }
+    }
+
+    /** Check that single-type import is not already imported or top-level defined,
+     *  but make an exception for two single-type imports which denote the same type.
+     *  @param pos                     Position for error reporting.
+     *  @param ordinallyImportedSoFar  A Scope containing types imported so far through
+     *                                 ordinary imports.
+     *  @param staticallyImportedSoFar A Scope containing types imported so far through
+     *                                 static imports.
+     *  @param topLevelScope           The current file's top-level Scope
+     *  @param sym                     The symbol.
+     *  @param staticImport            Whether or not this was a static import
+     */
+    private boolean checkUniqueImport(DiagnosticPosition pos, Scope ordinallyImportedSoFar,
+                                      Scope staticallyImportedSoFar, Scope topLevelScope,
+                                      Symbol sym, boolean staticImport) {
+        Filter<Symbol> duplicates = candidate -> candidate != sym && !candidate.type.isErroneous();
+        Symbol clashing = ordinallyImportedSoFar.findFirst(sym.name, duplicates);
+        if (clashing == null && !staticImport) {
+            clashing = staticallyImportedSoFar.findFirst(sym.name, duplicates);
+        }
+        if (clashing != null) {
+            if (staticImport)
+                log.error(pos, Errors.AlreadyDefinedStaticSingleImport(clashing));
+            else
+                log.error(pos, Errors.AlreadyDefinedSingleImport(clashing));
+            return false;
+        }
+        clashing = topLevelScope.findFirst(sym.name, duplicates);
+        if (clashing != null) {
+            log.error(pos, Errors.AlreadyDefinedThisUnit(clashing));
+            return false;
+        }
+        return true;
+    }
+
+    /** Check that a qualified name is in canonical form (for import decls).
+     */
+    public void checkCanonical(JCTree tree) {
+        if (!isCanonical(tree))
+            log.error(tree.pos(),
+                      Errors.ImportRequiresCanonical(TreeInfo.symbol(tree)));
+    }
+        // where
+        private boolean isCanonical(JCTree tree) {
+            while (tree.hasTag(SELECT)) {
+                JCFieldAccess s = (JCFieldAccess) tree;
+                if (s.sym.owner.name != TreeInfo.symbol(s.selected).name)
+                    return false;
+                tree = s.selected;
+            }
+            return true;
+        }
+
+    /** Check that an auxiliary class is not accessed from any other file than its own.
+     */
+    void checkForBadAuxiliaryClassAccess(DiagnosticPosition pos, Env<AttrContext> env, ClassSymbol c) {
+        if (lint.isEnabled(Lint.LintCategory.AUXILIARYCLASS) &&
+            (c.flags() & AUXILIARY) != 0 &&
+            rs.isAccessible(env, c) &&
+            !fileManager.isSameFile(c.sourcefile, env.toplevel.sourcefile))
+        {
+            log.warning(pos,
+                        Warnings.AuxiliaryClassAccessedFromOutsideOfItsSourceFile(c, c.sourcefile));
+        }
+    }
+
+    private class ConversionWarner extends Warner {
+        final String uncheckedKey;
+        final Type found;
+        final Type expected;
+        public ConversionWarner(DiagnosticPosition pos, String uncheckedKey, Type found, Type expected) {
+            super(pos);
+            this.uncheckedKey = uncheckedKey;
+            this.found = found;
+            this.expected = expected;
+        }
+
+        @Override
+        public void warn(LintCategory lint) {
+            boolean warned = this.warned;
+            super.warn(lint);
+            if (warned) return; // suppress redundant diagnostics
+            switch (lint) {
+                case UNCHECKED:
+                    Check.this.warnUnchecked(pos(), "prob.found.req", diags.fragment(uncheckedKey), found, expected);
+                    break;
+                case VARARGS:
+                    if (method != null &&
+                            method.attribute(syms.trustMeType.tsym) != null &&
+                            isTrustMeAllowedOnMethod(method) &&
+                            !types.isReifiable(method.type.getParameterTypes().last())) {
+                        Check.this.warnUnsafeVararg(pos(), "varargs.unsafe.use.varargs.param", method.params.last());
+                    }
+                    break;
+                default:
+                    throw new AssertionError("Unexpected lint: " + lint);
+            }
+        }
+    }
+
+    public Warner castWarner(DiagnosticPosition pos, Type found, Type expected) {
+        return new ConversionWarner(pos, "unchecked.cast.to.type", found, expected);
+    }
+
+    public Warner convertWarner(DiagnosticPosition pos, Type found, Type expected) {
+        return new ConversionWarner(pos, "unchecked.assign", found, expected);
+    }
+
+    public void checkFunctionalInterface(JCClassDecl tree, ClassSymbol cs) {
+        Compound functionalType = cs.attribute(syms.functionalInterfaceType.tsym);
+
+        if (functionalType != null) {
+            try {
+                types.findDescriptorSymbol((TypeSymbol)cs);
+            } catch (Types.FunctionDescriptorLookupError ex) {
+                DiagnosticPosition pos = tree.pos();
+                for (JCAnnotation a : tree.getModifiers().annotations) {
+                    if (a.annotationType.type.tsym == syms.functionalInterfaceType.tsym) {
+                        pos = a.pos();
+                        break;
+                    }
+                }
+                log.error(pos, Errors.BadFunctionalIntfAnno1(ex.getDiagnostic()));
+            }
+        }
+    }
+
+    public void checkImportsResolvable(final JCCompilationUnit toplevel) {
+        for (final JCImport imp : toplevel.getImports()) {
+            if (!imp.staticImport || !imp.qualid.hasTag(SELECT))
+                continue;
+            final JCFieldAccess select = (JCFieldAccess) imp.qualid;
+            final Symbol origin;
+            if (select.name == names.asterisk || (origin = TreeInfo.symbol(select.selected)) == null || origin.kind != TYP)
+                continue;
+
+            TypeSymbol site = (TypeSymbol) TreeInfo.symbol(select.selected);
+            if (!checkTypeContainsImportableElement(site, site, toplevel.packge, select.name, new HashSet<Symbol>())) {
+                log.error(imp.pos(),
+                          Errors.CantResolveLocation(KindName.STATIC,
+                                                     select.name,
+                                                     null,
+                                                     null,
+                                                     Fragments.Location(kindName(site),
+                                                                        site,
+                                                                        null)));
+            }
+        }
+    }
+
+    // Check that packages imported are in scope (JLS 7.4.3, 6.3, 6.5.3.1, 6.5.3.2)
+    public void checkImportedPackagesObservable(final JCCompilationUnit toplevel) {
+        OUTER: for (JCImport imp : toplevel.getImports()) {
+            if (!imp.staticImport && TreeInfo.name(imp.qualid) == names.asterisk) {
+                TypeSymbol tsym = ((JCFieldAccess)imp.qualid).selected.type.tsym;
+                if (toplevel.modle.visiblePackages != null) {
+                    //TODO - unclear: selects like javax.* will get resolved from the current module
+                    //(as javax is not an exported package from any module). And as javax in the current
+                    //module typically does not contain any classes or subpackages, we need to go through
+                    //the visible packages to find a sub-package:
+                    for (PackageSymbol known : toplevel.modle.visiblePackages.values()) {
+                        if (Convert.packagePart(known.fullname) == tsym.flatName())
+                            continue OUTER;
+                    }
+                }
+                if (tsym.kind == PCK && tsym.members().isEmpty() && !tsym.exists()) {
+                    log.error(DiagnosticFlag.RESOLVE_ERROR, imp.pos, Errors.DoesntExist(tsym));
+                }
+            }
+        }
+    }
+
+    private boolean checkTypeContainsImportableElement(TypeSymbol tsym, TypeSymbol origin, PackageSymbol packge, Name name, Set<Symbol> processed) {
+        if (tsym == null || !processed.add(tsym))
+            return false;
+
+            // also search through inherited names
+        if (checkTypeContainsImportableElement(types.supertype(tsym.type).tsym, origin, packge, name, processed))
+            return true;
+
+        for (Type t : types.interfaces(tsym.type))
+            if (checkTypeContainsImportableElement(t.tsym, origin, packge, name, processed))
+                return true;
+
+        for (Symbol sym : tsym.members().getSymbolsByName(name)) {
+            if (sym.isStatic() &&
+                importAccessible(sym, packge) &&
+                sym.isMemberOf(origin, types)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    // is the sym accessible everywhere in packge?
+    public boolean importAccessible(Symbol sym, PackageSymbol packge) {
+        try {
+            int flags = (int)(sym.flags() & AccessFlags);
+            switch (flags) {
+            default:
+            case PUBLIC:
+                return true;
+            case PRIVATE:
+                return false;
+            case 0:
+            case PROTECTED:
+                return sym.packge() == packge;
+            }
+        } catch (ClassFinder.BadClassFile err) {
+            throw err;
+        } catch (CompletionFailure ex) {
+            return false;
+        }
+    }
+
+    public void checkLeaksNotAccessible(Env<AttrContext> env, JCClassDecl check) {
+        JCCompilationUnit toplevel = env.toplevel;
+
+        if (   toplevel.modle == syms.unnamedModule
+            || toplevel.modle == syms.noModule
+            || (check.sym.flags() & COMPOUND) != 0) {
+            return ;
+        }
+
+        ExportsDirective currentExport = findExport(toplevel.packge);
+
+        if (   currentExport == null //not exported
+            || currentExport.modules != null) //don't check classes in qualified export
+            return ;
+
+        new TreeScanner() {
+            Lint lint = env.info.lint;
+            boolean inSuperType;
+
+            @Override
+            public void visitBlock(JCBlock tree) {
+            }
+            @Override
+            public void visitMethodDef(JCMethodDecl tree) {
+                if (!isAPISymbol(tree.sym))
+                    return;
+                Lint prevLint = lint;
+                try {
+                    lint = lint.augment(tree.sym);
+                    if (lint.isEnabled(LintCategory.EXPORTS)) {
+                        super.visitMethodDef(tree);
+                    }
+                } finally {
+                    lint = prevLint;
+                }
+            }
+            @Override
+            public void visitVarDef(JCVariableDecl tree) {
+                if (!isAPISymbol(tree.sym) && tree.sym.owner.kind != MTH)
+                    return;
+                Lint prevLint = lint;
+                try {
+                    lint = lint.augment(tree.sym);
+                    if (lint.isEnabled(LintCategory.EXPORTS)) {
+                        scan(tree.mods);
+                        scan(tree.vartype);
+                    }
+                } finally {
+                    lint = prevLint;
+                }
+            }
+            @Override
+            public void visitClassDef(JCClassDecl tree) {
+                if (tree != check)
+                    return ;
+
+                if (!isAPISymbol(tree.sym))
+                    return ;
+
+                Lint prevLint = lint;
+                try {
+                    lint = lint.augment(tree.sym);
+                    if (lint.isEnabled(LintCategory.EXPORTS)) {
+                        scan(tree.mods);
+                        scan(tree.typarams);
+                        try {
+                            inSuperType = true;
+                            scan(tree.extending);
+                            scan(tree.implementing);
+                        } finally {
+                            inSuperType = false;
+                        }
+                        scan(tree.defs);
+                    }
+                } finally {
+                    lint = prevLint;
+                }
+            }
+            @Override
+            public void visitTypeApply(JCTypeApply tree) {
+                scan(tree.clazz);
+                boolean oldInSuperType = inSuperType;
+                try {
+                    inSuperType = false;
+                    scan(tree.arguments);
+                } finally {
+                    inSuperType = oldInSuperType;
+                }
+            }
+            @Override
+            public void visitIdent(JCIdent tree) {
+                Symbol sym = TreeInfo.symbol(tree);
+                if (sym.kind == TYP && !sym.type.hasTag(TYPEVAR)) {
+                    checkVisible(tree.pos(), sym, toplevel.packge, inSuperType);
+                }
+            }
+
+            @Override
+            public void visitSelect(JCFieldAccess tree) {
+                Symbol sym = TreeInfo.symbol(tree);
+                Symbol sitesym = TreeInfo.symbol(tree.selected);
+                if (sym.kind == TYP && sitesym.kind == PCK) {
+                    checkVisible(tree.pos(), sym, toplevel.packge, inSuperType);
+                } else {
+                    super.visitSelect(tree);
+                }
+            }
+
+            @Override
+            public void visitAnnotation(JCAnnotation tree) {
+                if (tree.attribute.type.tsym.getAnnotation(java.lang.annotation.Documented.class) != null)
+                    super.visitAnnotation(tree);
+            }
+
+        }.scan(check);
+    }
+        //where:
+        private ExportsDirective findExport(PackageSymbol pack) {
+            for (ExportsDirective d : pack.modle.exports) {
+                if (d.packge == pack)
+                    return d;
+            }
+
+            return null;
+        }
+        private boolean isAPISymbol(Symbol sym) {
+            while (sym.kind != PCK) {
+                if ((sym.flags() & Flags.PUBLIC) == 0 && (sym.flags() & Flags.PROTECTED) == 0) {
+                    return false;
+                }
+                sym = sym.owner;
+            }
+            return true;
+        }
+        private void checkVisible(DiagnosticPosition pos, Symbol what, PackageSymbol inPackage, boolean inSuperType) {
+            if (!isAPISymbol(what) && !inSuperType) { //package private/private element
+                log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessible(kindName(what), what, what.packge().modle));
+                return ;
+            }
+
+            PackageSymbol whatPackage = what.packge();
+            ExportsDirective whatExport = findExport(whatPackage);
+            ExportsDirective inExport = findExport(inPackage);
+
+            if (whatExport == null) { //package not exported:
+                log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleUnexported(kindName(what), what, what.packge().modle));
+                return ;
+            }
+
+            if (whatExport.modules != null) {
+                if (inExport.modules == null || !whatExport.modules.containsAll(inExport.modules)) {
+                    log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleUnexportedQualified(kindName(what), what, what.packge().modle));
+                }
+            }
+
+            if (whatPackage.modle != inPackage.modle && whatPackage.modle != syms.java_base) {
+                //check that relativeTo.modle requires transitive what.modle, somehow:
+                List<ModuleSymbol> todo = List.of(inPackage.modle);
+
+                while (todo.nonEmpty()) {
+                    ModuleSymbol current = todo.head;
+                    todo = todo.tail;
+                    if (current == whatPackage.modle)
+                        return ; //OK
+                    for (RequiresDirective req : current.requires) {
+                        if (req.isTransitive()) {
+                            todo = todo.prepend(req.module);
+                        }
+                    }
+                }
+
+                log.warning(LintCategory.EXPORTS, pos, Warnings.LeaksNotAccessibleNotRequiredTransitive(kindName(what), what, what.packge().modle));
+            }
+        }
+
+    void checkModuleExists(final DiagnosticPosition pos, ModuleSymbol msym) {
+        if (msym.kind != MDL) {
+            deferredLintHandler.report(() -> {
+                if (lint.isEnabled(LintCategory.MODULE))
+                    log.warning(LintCategory.MODULE, pos, Warnings.ModuleNotFound(msym));
+            });
+        }
+    }
+
+    void checkPackageExistsForOpens(final DiagnosticPosition pos, PackageSymbol packge) {
+        if (packge.members().isEmpty() &&
+            ((packge.flags() & Flags.HAS_RESOURCE) == 0)) {
+            deferredLintHandler.report(() -> {
+                if (lint.isEnabled(LintCategory.OPENS))
+                    log.warning(pos, Warnings.PackageEmptyOrNotFound(packge));
+            });
+        }
+    }
+
+    void checkModuleRequires(final DiagnosticPosition pos, final RequiresDirective rd) {
+        if ((rd.module.flags() & Flags.AUTOMATIC_MODULE) != 0) {
+            deferredLintHandler.report(() -> {
+                if (rd.isTransitive() && lint.isEnabled(LintCategory.REQUIRES_TRANSITIVE_AUTOMATIC)) {
+                    log.warning(pos, Warnings.RequiresTransitiveAutomatic);
+                } else if (lint.isEnabled(LintCategory.REQUIRES_AUTOMATIC)) {
+                    log.warning(pos, Warnings.RequiresAutomatic);
+                }
+            });
+        }
+    }
+
+}