src/jdk.compiler/share/classes/com/sun/tools/javac/model/JavacElements.java
changeset 47216 71c04702a3d5
parent 43857 37614a3b7193
child 48054 702043a4cdeb
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/model/JavacElements.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,779 @@
+/*
+ * Copyright (c) 2005, 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.model;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import javax.lang.model.AnnotatedConstruct;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.*;
+import javax.lang.model.type.DeclaredType;
+import javax.lang.model.util.Elements;
+import javax.tools.JavaFileObject;
+import static javax.lang.model.util.ElementFilter.methodsIn;
+
+import com.sun.source.util.JavacTask;
+import com.sun.tools.javac.api.JavacTaskImpl;
+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.ExportsFlag;
+import com.sun.tools.javac.code.Directive.OpensDirective;
+import com.sun.tools.javac.code.Directive.OpensFlag;
+import com.sun.tools.javac.code.Directive.RequiresDirective;
+import com.sun.tools.javac.code.Directive.RequiresFlag;
+import com.sun.tools.javac.code.Scope.WriteableScope;
+import com.sun.tools.javac.code.Symbol.*;
+import com.sun.tools.javac.comp.AttrContext;
+import com.sun.tools.javac.comp.Enter;
+import com.sun.tools.javac.comp.Env;
+import com.sun.tools.javac.main.JavaCompiler;
+import com.sun.tools.javac.processing.PrintingProcessor;
+import com.sun.tools.javac.tree.JCTree;
+import com.sun.tools.javac.tree.JCTree.*;
+import com.sun.tools.javac.tree.TreeInfo;
+import com.sun.tools.javac.tree.TreeScanner;
+import com.sun.tools.javac.util.*;
+import com.sun.tools.javac.util.DefinedBy.Api;
+import com.sun.tools.javac.util.Name;
+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.CLASS;
+import com.sun.tools.javac.comp.Modules;
+import com.sun.tools.javac.comp.Resolve;
+import com.sun.tools.javac.comp.Resolve.RecoveryLoadClass;
+import com.sun.tools.javac.resources.CompilerProperties.Notes;
+import static com.sun.tools.javac.tree.JCTree.Tag.*;
+
+/**
+ * Utility methods for operating on program elements.
+ *
+ * <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></p>
+ */
+public class JavacElements implements Elements {
+
+    private final JavaCompiler javaCompiler;
+    private final Symtab syms;
+    private final Modules modules;
+    private final Names names;
+    private final Types types;
+    private final Enter enter;
+    private final Resolve resolve;
+    private final JavacTaskImpl javacTaskImpl;
+    private final Log log;
+    private final boolean allowModules;
+
+    public static JavacElements instance(Context context) {
+        JavacElements instance = context.get(JavacElements.class);
+        if (instance == null)
+            instance = new JavacElements(context);
+        return instance;
+    }
+
+    protected JavacElements(Context context) {
+        context.put(JavacElements.class, this);
+        javaCompiler = JavaCompiler.instance(context);
+        syms = Symtab.instance(context);
+        modules = Modules.instance(context);
+        names = Names.instance(context);
+        types = Types.instance(context);
+        enter = Enter.instance(context);
+        resolve = Resolve.instance(context);
+        JavacTask t = context.get(JavacTask.class);
+        javacTaskImpl = t instanceof JavacTaskImpl ? (JavacTaskImpl) t : null;
+        log = Log.instance(context);
+        Source source = Source.instance(context);
+        allowModules = source.allowModules();
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public Set<? extends ModuleElement> getAllModuleElements() {
+        if (allowModules)
+            return Collections.unmodifiableSet(modules.allModules());
+        else
+            return Collections.emptySet();
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public ModuleSymbol getModuleElement(CharSequence name) {
+        ensureEntered("getModuleElement");
+        if (modules.getDefaultModule() == syms.noModule)
+            return null;
+        String strName = name.toString();
+        if (strName.equals(""))
+            return syms.unnamedModule;
+        return modules.getObservableModule(names.fromString(strName));
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public PackageSymbol getPackageElement(CharSequence name) {
+        return doGetPackageElement(null, name);
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public PackageSymbol getPackageElement(ModuleElement module, CharSequence name) {
+        module.getClass();
+        return doGetPackageElement(module, name);
+    }
+
+    private PackageSymbol doGetPackageElement(ModuleElement module, CharSequence name) {
+        ensureEntered("getPackageElement");
+        return doGetElement(module, "getPackageElement", name, PackageSymbol.class);
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public ClassSymbol getTypeElement(CharSequence name) {
+        return doGetTypeElement(null, name);
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public ClassSymbol getTypeElement(ModuleElement module, CharSequence name) {
+        module.getClass();
+
+        return doGetTypeElement(module, name);
+    }
+
+    private ClassSymbol doGetTypeElement(ModuleElement module, CharSequence name) {
+        ensureEntered("getTypeElement");
+        return doGetElement(module, "getTypeElement", name, ClassSymbol.class);
+    }
+
+    private <S extends Symbol> S doGetElement(ModuleElement module, String methodName,
+                                              CharSequence name, Class<S> clazz) {
+        String strName = name.toString();
+        if (!SourceVersion.isName(strName) && (!strName.isEmpty() || clazz == ClassSymbol.class)) {
+            return null;
+        }
+        if (module == null) {
+            return unboundNameToSymbol(methodName, strName, clazz);
+        } else {
+            return nameToSymbol((ModuleSymbol) module, strName, clazz);
+        }
+    }
+
+    private final Set<String> alreadyWarnedDuplicates = new HashSet<>();
+
+    private <S extends Symbol> S unboundNameToSymbol(String methodName,
+                                                     String nameStr,
+                                                     Class<S> clazz) {
+        if (modules.getDefaultModule() == syms.noModule) { //not a modular mode:
+            return nameToSymbol(syms.noModule, nameStr, clazz);
+        }
+
+        Set<S> found = new LinkedHashSet<>();
+
+        for (ModuleSymbol msym : modules.allModules()) {
+            S sym = nameToSymbol(msym, nameStr, clazz);
+
+            if (sym != null) {
+                if (!allowModules || clazz == ClassSymbol.class || !sym.members().isEmpty()) {
+                    //do not add packages without members:
+                    found.add(sym);
+                }
+            }
+        }
+
+        if (found.size() == 1) {
+            return found.iterator().next();
+        } else if (found.size() > 1) {
+            //more than one element found, produce a note:
+            if (alreadyWarnedDuplicates.add(methodName + ":" + nameStr)) {
+                String moduleNames = found.stream()
+                                          .map(s -> s.packge().modle)
+                                          .map(m -> m.toString())
+                                          .collect(Collectors.joining(", "));
+                log.note(Notes.MultipleElements(methodName, nameStr, moduleNames));
+            }
+            return null;
+        } else {
+            //not found, or more than one element found:
+            return null;
+        }
+    }
+
+    /**
+     * Returns a symbol given the type's or package's canonical name,
+     * or null if the name isn't found.
+     */
+    private <S extends Symbol> S nameToSymbol(ModuleSymbol module, String nameStr, Class<S> clazz) {
+        Name name = names.fromString(nameStr);
+        // First check cache.
+        Symbol sym = (clazz == ClassSymbol.class)
+                    ? syms.getClass(module, name)
+                    : syms.lookupPackage(module, name);
+
+        try {
+            if (sym == null)
+                sym = javaCompiler.resolveIdent(module, nameStr);
+
+            sym.complete();
+
+            return (sym.kind != ERR &&
+                    sym.exists() &&
+                    clazz.isInstance(sym) &&
+                    name.equals(sym.getQualifiedName()))
+                ? clazz.cast(sym)
+                : null;
+        } catch (CompletionFailure e) {
+            return null;
+        }
+    }
+
+    /**
+     * Returns the tree for an annotation given the annotated element
+     * and the element's own tree.  Returns null if the tree cannot be found.
+     */
+    private JCTree matchAnnoToTree(AnnotationMirror findme,
+                                   Element e, JCTree tree) {
+        Symbol sym = cast(Symbol.class, e);
+        class Vis extends JCTree.Visitor {
+            List<JCAnnotation> result = null;
+            public void visitPackageDef(JCPackageDecl tree) {
+                result = tree.annotations;
+            }
+            public void visitClassDef(JCClassDecl tree) {
+                result = tree.mods.annotations;
+            }
+            public void visitMethodDef(JCMethodDecl tree) {
+                result = tree.mods.annotations;
+            }
+            public void visitVarDef(JCVariableDecl tree) {
+                result = tree.mods.annotations;
+            }
+            @Override
+            public void visitTypeParameter(JCTypeParameter tree) {
+                result = tree.annotations;
+            }
+        }
+        Vis vis = new Vis();
+        tree.accept(vis);
+        if (vis.result == null)
+            return null;
+
+        List<Attribute.Compound> annos = sym.getAnnotationMirrors();
+        return matchAnnoToTree(cast(Attribute.Compound.class, findme),
+                               annos,
+                               vis.result);
+    }
+
+    /**
+     * Returns the tree for an annotation given a list of annotations
+     * in which to search (recursively) and their corresponding trees.
+     * Returns null if the tree cannot be found.
+     */
+    private JCTree matchAnnoToTree(Attribute.Compound findme,
+                                   List<Attribute.Compound> annos,
+                                   List<JCAnnotation> trees) {
+        for (Attribute.Compound anno : annos) {
+            for (JCAnnotation tree : trees) {
+                if (tree.type.tsym != anno.type.tsym)
+                    continue;
+                JCTree match = matchAttributeToTree(findme, anno, tree);
+                if (match != null)
+                    return match;
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Returns the tree for an attribute given an enclosing attribute to
+     * search (recursively) and the enclosing attribute's corresponding tree.
+     * Returns null if the tree cannot be found.
+     */
+    private JCTree matchAttributeToTree(final Attribute findme,
+                                        final Attribute attr,
+                                        final JCTree tree) {
+        if (attr == findme)
+            return tree;
+
+        class Vis implements Attribute.Visitor {
+            JCTree result = null;
+            public void visitConstant(Attribute.Constant value) {
+            }
+            public void visitClass(Attribute.Class clazz) {
+            }
+            public void visitCompound(Attribute.Compound anno) {
+                for (Pair<MethodSymbol, Attribute> pair : anno.values) {
+                    JCExpression expr = scanForAssign(pair.fst, tree);
+                    if (expr != null) {
+                        JCTree match = matchAttributeToTree(findme, pair.snd, expr);
+                        if (match != null) {
+                            result = match;
+                            return;
+                        }
+                    }
+                }
+            }
+            public void visitArray(Attribute.Array array) {
+                if (tree.hasTag(NEWARRAY)) {
+                    List<JCExpression> elems = ((JCNewArray)tree).elems;
+                    for (Attribute value : array.values) {
+                        JCTree match = matchAttributeToTree(findme, value, elems.head);
+                        if (match != null) {
+                            result = match;
+                            return;
+                        }
+                        elems = elems.tail;
+                    }
+                } else if (array.values.length == 1) {
+                    // the tree may not be a NEWARRAY for single-element array initializers
+                    result = matchAttributeToTree(findme, array.values[0], tree);
+                }
+            }
+            public void visitEnum(Attribute.Enum e) {
+            }
+            public void visitError(Attribute.Error e) {
+            }
+        }
+        Vis vis = new Vis();
+        attr.accept(vis);
+        return vis.result;
+    }
+
+    /**
+     * Scans for a JCAssign node with a LHS matching a given
+     * symbol, and returns its RHS.  Does not scan nested JCAnnotations.
+     */
+    private JCExpression scanForAssign(final MethodSymbol sym,
+                                       final JCTree tree) {
+        class TS extends TreeScanner {
+            JCExpression result = null;
+            public void scan(JCTree t) {
+                if (t != null && result == null)
+                    t.accept(this);
+            }
+            public void visitAnnotation(JCAnnotation t) {
+                if (t == tree)
+                    scan(t.args);
+            }
+            public void visitAssign(JCAssign t) {
+                if (t.lhs.hasTag(IDENT)) {
+                    JCIdent ident = (JCIdent) t.lhs;
+                    if (ident.sym == sym)
+                        result = t.rhs;
+                }
+            }
+        }
+        TS scanner = new TS();
+        tree.accept(scanner);
+        return scanner.result;
+    }
+
+    /**
+     * Returns the tree node corresponding to this element, or null
+     * if none can be found.
+     */
+    public JCTree getTree(Element e) {
+        Pair<JCTree, ?> treeTop = getTreeAndTopLevel(e);
+        return (treeTop != null) ? treeTop.fst : null;
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public String getDocComment(Element e) {
+        // Our doc comment is contained in a map in our toplevel,
+        // indexed by our tree.  Find our enter environment, which gives
+        // us our toplevel.  It also gives us a tree that contains our
+        // tree:  walk it to find our tree.  This is painful.
+        Pair<JCTree, JCCompilationUnit> treeTop = getTreeAndTopLevel(e);
+        if (treeTop == null)
+            return null;
+        JCTree tree = treeTop.fst;
+        JCCompilationUnit toplevel = treeTop.snd;
+        if (toplevel.docComments == null)
+            return null;
+        return toplevel.docComments.getCommentText(tree);
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public PackageElement getPackageOf(Element e) {
+        return cast(Symbol.class, e).packge();
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public ModuleElement getModuleOf(Element e) {
+        Symbol sym = cast(Symbol.class, e);
+        if (modules.getDefaultModule() == syms.noModule)
+            return null;
+        return (sym.kind == MDL) ? ((ModuleElement) e) : sym.packge().modle;
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public boolean isDeprecated(Element e) {
+        Symbol sym = cast(Symbol.class, e);
+        sym.complete();
+        return sym.isDeprecated();
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public Origin getOrigin(Element e) {
+        Symbol sym = cast(Symbol.class, e);
+        if ((sym.flags() & Flags.GENERATEDCONSTR) != 0)
+            return Origin.MANDATED;
+        //TypeElement.getEnclosedElements does not return synthetic elements,
+        //and most synthetic elements are not read from the classfile anyway:
+        return Origin.EXPLICIT;
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public Origin getOrigin(AnnotatedConstruct c, AnnotationMirror a) {
+        Compound ac = cast(Compound.class, a);
+        if (ac.isSynthesized())
+            return Origin.MANDATED;
+        return Origin.EXPLICIT;
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public Origin getOrigin(ModuleElement m, ModuleElement.Directive directive) {
+        switch (directive.getKind()) {
+            case REQUIRES:
+                RequiresDirective rd = cast(RequiresDirective.class, directive);
+                if (rd.flags.contains(RequiresFlag.MANDATED))
+                    return Origin.MANDATED;
+                if (rd.flags.contains(RequiresFlag.SYNTHETIC))
+                    return Origin.SYNTHETIC;
+                return Origin.EXPLICIT;
+            case EXPORTS:
+                ExportsDirective ed = cast(ExportsDirective.class, directive);
+                if (ed.flags.contains(ExportsFlag.MANDATED))
+                    return Origin.MANDATED;
+                if (ed.flags.contains(ExportsFlag.SYNTHETIC))
+                    return Origin.SYNTHETIC;
+                return Origin.EXPLICIT;
+            case OPENS:
+                OpensDirective od = cast(OpensDirective.class, directive);
+                if (od.flags.contains(OpensFlag.MANDATED))
+                    return Origin.MANDATED;
+                if (od.flags.contains(OpensFlag.SYNTHETIC))
+                    return Origin.SYNTHETIC;
+                return Origin.EXPLICIT;
+        }
+        return Origin.EXPLICIT;
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public Name getBinaryName(TypeElement type) {
+        return cast(TypeSymbol.class, type).flatName();
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public Map<MethodSymbol, Attribute> getElementValuesWithDefaults(
+                                                        AnnotationMirror a) {
+        Attribute.Compound anno = cast(Attribute.Compound.class, a);
+        DeclaredType annotype = a.getAnnotationType();
+        Map<MethodSymbol, Attribute> valmap = anno.getElementValues();
+
+        for (ExecutableElement ex :
+                 methodsIn(annotype.asElement().getEnclosedElements())) {
+            MethodSymbol meth = (MethodSymbol) ex;
+            Attribute defaultValue = meth.getDefaultValue();
+            if (defaultValue != null && !valmap.containsKey(meth)) {
+                valmap.put(meth, defaultValue);
+            }
+        }
+        return valmap;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public FilteredMemberList getAllMembers(TypeElement element) {
+        Symbol sym = cast(Symbol.class, element);
+        WriteableScope scope = sym.members().dupUnshared();
+        List<Type> closure = types.closure(sym.asType());
+        for (Type t : closure)
+            addMembers(scope, t);
+        return new FilteredMemberList(scope);
+    }
+    // where
+        private void addMembers(WriteableScope scope, Type type) {
+            members:
+            for (Symbol e : type.asElement().members().getSymbols(NON_RECURSIVE)) {
+                for (Symbol overrider : scope.getSymbolsByName(e.getSimpleName())) {
+                    if (overrider.kind == e.kind && (overrider.flags() & Flags.SYNTHETIC) == 0) {
+                        if (overrider.getKind() == ElementKind.METHOD &&
+                                overrides((ExecutableElement)overrider, (ExecutableElement)e, (TypeElement)type.asElement())) {
+                            continue members;
+                        }
+                    }
+                }
+                boolean derived = e.getEnclosingElement() != scope.owner;
+                ElementKind kind = e.getKind();
+                boolean initializer = kind == ElementKind.CONSTRUCTOR
+                    || kind == ElementKind.INSTANCE_INIT
+                    || kind == ElementKind.STATIC_INIT;
+                if (!derived || (!initializer && e.isInheritedIn(scope.owner, types)))
+                    scope.enter(e);
+            }
+        }
+
+    /**
+     * Returns all annotations of an element, whether
+     * inherited or directly present.
+     *
+     * @param e  the element being examined
+     * @return all annotations of the element
+     */
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public List<Attribute.Compound> getAllAnnotationMirrors(Element e) {
+        Symbol sym = cast(Symbol.class, e);
+        List<Attribute.Compound> annos = sym.getAnnotationMirrors();
+        while (sym.getKind() == ElementKind.CLASS) {
+            Type sup = ((ClassSymbol) sym).getSuperclass();
+            if (!sup.hasTag(CLASS) || sup.isErroneous() ||
+                    sup.tsym == syms.objectType.tsym) {
+                break;
+            }
+            sym = sup.tsym;
+            List<Attribute.Compound> oldAnnos = annos;
+            List<Attribute.Compound> newAnnos = sym.getAnnotationMirrors();
+            for (Attribute.Compound anno : newAnnos) {
+                if (isInherited(anno.type) &&
+                        !containsAnnoOfType(oldAnnos, anno.type)) {
+                    annos = annos.prepend(anno);
+                }
+            }
+        }
+        return annos;
+    }
+
+    /**
+     * Tests whether an annotation type is @Inherited.
+     */
+    private boolean isInherited(Type annotype) {
+        return annotype.tsym.attribute(syms.inheritedType.tsym) != null;
+    }
+
+    /**
+     * Tests whether a list of annotations contains an annotation
+     * of a given type.
+     */
+    private static boolean containsAnnoOfType(List<Attribute.Compound> annos,
+                                              Type type) {
+        for (Attribute.Compound anno : annos) {
+            if (anno.type.tsym == type.tsym)
+                return true;
+        }
+        return false;
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public boolean hides(Element hiderEl, Element hideeEl) {
+        Symbol hider = cast(Symbol.class, hiderEl);
+        Symbol hidee = cast(Symbol.class, hideeEl);
+
+        // Fields only hide fields; methods only methods; types only types.
+        // Names must match.  Nothing hides itself (just try it).
+        if (hider == hidee ||
+                hider.kind != hidee.kind ||
+                hider.name != hidee.name) {
+            return false;
+        }
+
+        // Only static methods can hide other methods.
+        // Methods only hide methods with matching signatures.
+        if (hider.kind == MTH) {
+            if (!hider.isStatic() ||
+                        !types.isSubSignature(hider.type, hidee.type)) {
+                return false;
+            }
+        }
+
+        // Hider must be in a subclass of hidee's class.
+        // Note that if M1 hides M2, and M2 hides M3, and M3 is accessible
+        // in M1's class, then M1 and M2 both hide M3.
+        ClassSymbol hiderClass = hider.owner.enclClass();
+        ClassSymbol hideeClass = hidee.owner.enclClass();
+        if (hiderClass == null || hideeClass == null ||
+                !hiderClass.isSubClass(hideeClass, types)) {
+            return false;
+        }
+
+        // Hidee must be accessible in hider's class.
+        // The method isInheritedIn is poorly named:  it checks only access.
+        return hidee.isInheritedIn(hiderClass, types);
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public boolean overrides(ExecutableElement riderEl,
+                             ExecutableElement rideeEl, TypeElement typeEl) {
+        MethodSymbol rider = cast(MethodSymbol.class, riderEl);
+        MethodSymbol ridee = cast(MethodSymbol.class, rideeEl);
+        ClassSymbol origin = cast(ClassSymbol.class, typeEl);
+
+        return rider.name == ridee.name &&
+
+               // not reflexive as per JLS
+               rider != ridee &&
+
+               // we don't care if ridee is static, though that wouldn't
+               // compile
+               !rider.isStatic() &&
+
+               // Symbol.overrides assumes the following
+               ridee.isMemberOf(origin, types) &&
+
+               // check access and signatures; don't check return types
+               rider.overrides(ridee, origin, types, false);
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public String getConstantExpression(Object value) {
+        return Constants.format(value);
+    }
+
+    /**
+     * Print a representation of the elements to the given writer in
+     * the specified order.  The main purpose of this method is for
+     * diagnostics.  The exact format of the output is <em>not</em>
+     * specified and is subject to change.
+     *
+     * @param w the writer to print the output to
+     * @param elements the elements to print
+     */
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public void printElements(java.io.Writer w, Element... elements) {
+        for (Element element : elements)
+            (new PrintingProcessor.PrintingElementVisitor(w, this)).visit(element).flush();
+    }
+
+    @DefinedBy(Api.LANGUAGE_MODEL)
+    public Name getName(CharSequence cs) {
+        return names.fromString(cs.toString());
+    }
+
+    @Override @DefinedBy(Api.LANGUAGE_MODEL)
+    public boolean isFunctionalInterface(TypeElement element) {
+        if (element.getKind() != ElementKind.INTERFACE)
+            return false;
+        else {
+            TypeSymbol tsym = cast(TypeSymbol.class, element);
+            return types.isFunctionalInterface(tsym);
+        }
+    }
+
+    /**
+     * Returns the tree node and compilation unit corresponding to this
+     * element, or null if they can't be found.
+     */
+    private Pair<JCTree, JCCompilationUnit> getTreeAndTopLevel(Element e) {
+        Symbol sym = cast(Symbol.class, e);
+        Env<AttrContext> enterEnv = getEnterEnv(sym);
+        if (enterEnv == null)
+            return null;
+        JCTree tree = TreeInfo.declarationFor(sym, enterEnv.tree);
+        if (tree == null || enterEnv.toplevel == null)
+            return null;
+        return new Pair<>(tree, enterEnv.toplevel);
+    }
+
+    /**
+     * Returns the best approximation for the tree node and compilation unit
+     * corresponding to the given element, annotation and value.
+     * If the element is null, null is returned.
+     * If the annotation is null or cannot be found, the tree node and
+     * compilation unit for the element is returned.
+     * If the annotation value is null or cannot be found, the tree node and
+     * compilation unit for the annotation is returned.
+     */
+    public Pair<JCTree, JCCompilationUnit> getTreeAndTopLevel(
+                      Element e, AnnotationMirror a, AnnotationValue v) {
+        if (e == null)
+            return null;
+
+        Pair<JCTree, JCCompilationUnit> elemTreeTop = getTreeAndTopLevel(e);
+        if (elemTreeTop == null)
+            return null;
+
+        if (a == null)
+            return elemTreeTop;
+
+        JCTree annoTree = matchAnnoToTree(a, e, elemTreeTop.fst);
+        if (annoTree == null)
+            return elemTreeTop;
+
+        if (v == null)
+            return new Pair<>(annoTree, elemTreeTop.snd);
+
+        JCTree valueTree = matchAttributeToTree(
+                cast(Attribute.class, v), cast(Attribute.class, a), annoTree);
+        if (valueTree == null)
+            return new Pair<>(annoTree, elemTreeTop.snd);
+
+        return new Pair<>(valueTree, elemTreeTop.snd);
+    }
+
+    /**
+     * Returns a symbol's enter environment, or null if it has none.
+     */
+    private Env<AttrContext> getEnterEnv(Symbol sym) {
+        // Get enclosing class of sym, or sym itself if it is a class
+        // package, or module.
+        TypeSymbol ts = null;
+        switch (sym.kind) {
+            case PCK:
+                ts = (PackageSymbol)sym;
+                break;
+            case MDL:
+                ts = (ModuleSymbol)sym;
+                break;
+            default:
+                ts = sym.enclClass();
+        }
+        return (ts != null)
+                ? enter.getEnv(ts)
+                : null;
+    }
+
+    private void ensureEntered(String methodName) {
+        if (javacTaskImpl != null) {
+            javacTaskImpl.ensureEntered();
+        }
+        if (!javaCompiler.isEnterDone()) {
+            throw new IllegalStateException("Cannot use Elements." + methodName + " before the TaskEvent.Kind.ENTER finished event.");
+        }
+    }
+
+    /**
+     * Returns an object cast to the specified type.
+     * @throws NullPointerException if the object is {@code null}
+     * @throws IllegalArgumentException if the object is of the wrong type
+     */
+    private static <T> T cast(Class<T> clazz, Object o) {
+        if (! clazz.isInstance(o))
+            throw new IllegalArgumentException(o.toString());
+        return clazz.cast(o);
+    }
+}