--- a/langtools/src/share/classes/com/sun/tools/javac/comp/Infer.java	Wed Jan 18 18:26:36 2012 -0800
+++ b/langtools/src/share/classes/com/sun/tools/javac/comp/Infer.java	Tue Jan 24 17:52:02 2012 +0000
@@ -34,6 +34,7 @@
 import com.sun.tools.javac.code.Type.*;
 import com.sun.tools.javac.code.Type.ForAll.ConstraintKind;
 import com.sun.tools.javac.code.Symbol.*;
+import com.sun.tools.javac.comp.Resolve.InapplicableMethodException;
 import com.sun.tools.javac.comp.Resolve.VerboseResolutionMode;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
 
@@ -84,7 +85,7 @@
 
     }
 
-    public static class InferenceException extends Resolve.InapplicableMethodException {
+    public static class InferenceException extends InapplicableMethodException {
         private static final long serialVersionUID = 0;
 
         InferenceException(JCDiagnostic.Factory diags) {
@@ -287,6 +288,18 @@
         }
     }
 
+    Type asUndetType(Type t, List<Type> undetvars) {
+        return types.subst(t, inferenceVars(undetvars), undetvars);
+    }
+
+    List<Type> inferenceVars(List<Type> undetvars) {
+        ListBuffer<Type> tvars = ListBuffer.lb();
+        for (Type uv : undetvars) {
+            tvars.append(((UndetVar)uv).qtype);
+        }
+        return tvars.toList();
+    }
+
 /***************************************************************************
  * Exported Methods
  ***************************************************************************/
@@ -372,62 +385,11 @@
                                   final Warner warn) throws InferenceException {
         //-System.err.println("instantiateMethod(" + tvars + ", " + mt + ", " + argtypes + ")"); //DEBUG
         List<Type> undetvars = Type.map(tvars, fromTypeVarFun);
-        List<Type> formals = mt.argtypes;
-        //need to capture exactly once - otherwise subsequent
-        //applicability checks might fail
-        final List<Type> capturedArgs = types.capture(argtypes);
-        List<Type> actuals = capturedArgs;
-        List<Type> actualsNoCapture = argtypes;
-        // instantiate all polymorphic argument types and
-        // set up lower bounds constraints for undetvars
-        Type varargsFormal = useVarargs ? formals.last() : null;
-        if (varargsFormal == null &&
-                actuals.size() != formals.size()) {
-            throw unambiguousNoInstanceException
-                .setMessage("infer.arg.length.mismatch");
-        }
-        while (actuals.nonEmpty() && formals.head != varargsFormal) {
-            Type formal = formals.head;
-            Type actual = actuals.head.baseType();
-            Type actualNoCapture = actualsNoCapture.head.baseType();
-            if (actual.tag == FORALL)
-                actual = instantiateArg((ForAll)actual, formal, tvars, warn);
-            Type undetFormal = types.subst(formal, tvars, undetvars);
-            boolean works = allowBoxing
-                ? types.isConvertible(actual, undetFormal, warn)
-                : types.isSubtypeUnchecked(actual, undetFormal, warn);
-            if (!works) {
-                throw unambiguousNoInstanceException
-                    .setMessage("infer.no.conforming.assignment.exists",
-                                tvars, actualNoCapture, formal);
-            }
-            formals = formals.tail;
-            actuals = actuals.tail;
-            actualsNoCapture = actualsNoCapture.tail;
-        }
+        //final List<Type> capturedArgs = types.capture(argtypes);
 
-        if (formals.head != varargsFormal) // not enough args
-            throw unambiguousNoInstanceException.setMessage("infer.arg.length.mismatch");
-
-        // for varargs arguments as well
-        if (useVarargs) {
-            Type elemType = types.elemtype(varargsFormal);
-            Type elemUndet = types.subst(elemType, tvars, undetvars);
-            while (actuals.nonEmpty()) {
-                Type actual = actuals.head.baseType();
-                Type actualNoCapture = actualsNoCapture.head.baseType();
-                if (actual.tag == FORALL)
-                    actual = instantiateArg((ForAll)actual, elemType, tvars, warn);
-                boolean works = types.isConvertible(actual, elemUndet, warn);
-                if (!works) {
-                    throw unambiguousNoInstanceException
-                        .setMessage("infer.no.conforming.assignment.exists",
-                                    tvars, actualNoCapture, elemType);
-                }
-                actuals = actuals.tail;
-                actualsNoCapture = actualsNoCapture.tail;
-            }
-        }
+        final List<Type> capturedArgs =
+                rs.checkRawArgumentsAcceptable(env, undetvars, argtypes, mt.getParameterTypes(),
+                    allowBoxing, useVarargs, warn, new InferenceCheckHandler(undetvars));
 
         // minimize as yet undetermined type variables
         for (Type t : undetvars)
@@ -503,6 +465,31 @@
     }
     //where
 
+        /** inference check handler **/
+        class InferenceCheckHandler implements Resolve.MethodCheckHandler {
+
+            List<Type> undetvars;
+
+            public InferenceCheckHandler(List<Type> undetvars) {
+                this.undetvars = undetvars;
+            }
+
+            public InapplicableMethodException arityMismatch() {
+                return unambiguousNoInstanceException.setMessage("infer.arg.length.mismatch");
+            }
+            public InapplicableMethodException argumentMismatch(boolean varargs, Type found, Type expected) {
+                String key = varargs ?
+                    "infer.varargs.argument.mismatch" :
+                    "infer.no.conforming.assignment.exists";
+                return unambiguousNoInstanceException.setMessage(key,
+                        inferenceVars(undetvars), found, expected);
+            }
+            public InapplicableMethodException inaccessibleVarargs(Symbol location, Type expected) {
+                return unambiguousNoInstanceException.setMessage("inaccessible.varargs.type",
+                        expected, Kinds.kindName(location), location);
+            }
+        }
+
         /**
          * A delegated type representing a partially uninferred method type.
          * The return type of a partially uninferred method type is a ForAll
@@ -572,7 +559,7 @@
                 rs.checkRawArgumentsAcceptable(env, actuals, formals,
                        allowBoxing, useVarargs, warn);
             }
-            catch (Resolve.InapplicableMethodException ex) {
+            catch (InapplicableMethodException ex) {
                 // inferred method is not applicable
                 throw invalidInstanceException.setMessage(ex.getDiagnostic());
             }

--- a/langtools/src/share/classes/com/sun/tools/javac/comp/Resolve.java	Wed Jan 18 18:26:36 2012 -0800
+++ b/langtools/src/share/classes/com/sun/tools/javac/comp/Resolve.java	Tue Jan 24 17:52:02 2012 +0000
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2012, 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
@@ -474,52 +474,126 @@
             return false;
         }
     }
+    /**
+     * A check handler is used by the main method applicability routine in order
+     * to handle specific method applicability failures. It is assumed that a class
+     * implementing this interface should throw exceptions that are a subtype of
+     * InapplicableMethodException (see below). Such exception will terminate the
+     * method applicability check and propagate important info outwards (for the
+     * purpose of generating better diagnostics).
+     */
+    interface MethodCheckHandler {
+        /* The number of actuals and formals differ */
+        InapplicableMethodException arityMismatch();
+        /* An actual argument type does not conform to the corresponding formal type */
+        InapplicableMethodException argumentMismatch(boolean varargs, Type found, Type expected);
+        /* The element type of a varargs is not accessible in the current context */
+        InapplicableMethodException inaccessibleVarargs(Symbol location, Type expected);
+    }
+
+    /**
+     * Basic method check handler used within Resolve - all methods end up
+     * throwing InapplicableMethodException; a diagnostic fragment that describes
+     * the cause as to why the method is not applicable is set on the exception
+     * before it is thrown.
+     */
+    MethodCheckHandler resolveHandler = new MethodCheckHandler() {
+            public InapplicableMethodException arityMismatch() {
+                return inapplicableMethodException.setMessage("arg.length.mismatch");
+            }
+            public InapplicableMethodException argumentMismatch(boolean varargs, Type found, Type expected) {
+                String key = varargs ?
+                        "varargs.argument.mismatch" :
+                        "no.conforming.assignment.exists";
+                return inapplicableMethodException.setMessage(key,
+                        found, expected);
+            }
+            public InapplicableMethodException inaccessibleVarargs(Symbol location, Type expected) {
+                return inapplicableMethodException.setMessage("inaccessible.varargs.type",
+                        expected, Kinds.kindName(location), location);
+            }
+    };
+
     void checkRawArgumentsAcceptable(Env<AttrContext> env,
                                 List<Type> argtypes,
                                 List<Type> formals,
                                 boolean allowBoxing,
                                 boolean useVarargs,
                                 Warner warn) {
+        checkRawArgumentsAcceptable(env, List.<Type>nil(), argtypes, formals,
+                allowBoxing, useVarargs, warn, resolveHandler);
+    }
+
+    /**
+     * Main method applicability routine. Given a list of actual types A,
+     * a list of formal types F, determines whether the types in A are
+     * compatible (by method invocation conversion) with the types in F.
+     *
+     * Since this routine is shared between overload resolution and method
+     * type-inference, it is crucial that actual types are converted to the
+     * corresponding 'undet' form (i.e. where inference variables are replaced
+     * with undetvars) so that constraints can be propagated and collected.
+     *
+     * Moreover, if one or more types in A is a poly type, this routine calls
+     * Infer.instantiateArg in order to complete the poly type (this might involve
+     * deferred attribution).
+     *
+     * A method check handler (see above) is used in order to report errors.
+     */
+    List<Type> checkRawArgumentsAcceptable(Env<AttrContext> env,
+                                List<Type> undetvars,
+                                List<Type> argtypes,
+                                List<Type> formals,
+                                boolean allowBoxing,
+                                boolean useVarargs,
+                                Warner warn,
+                                MethodCheckHandler handler) {
         Type varargsFormal = useVarargs ? formals.last() : null;
+        ListBuffer<Type> checkedArgs = ListBuffer.lb();
+
         if (varargsFormal == null &&
                 argtypes.size() != formals.size()) {
-            throw inapplicableMethodException.setMessage("arg.length.mismatch"); // not enough args
+            throw handler.arityMismatch(); // not enough args
         }
 
         while (argtypes.nonEmpty() && formals.head != varargsFormal) {
-            boolean works = allowBoxing
-                ? types.isConvertible(argtypes.head, formals.head, warn)
-                : types.isSubtypeUnchecked(argtypes.head, formals.head, warn);
-            if (!works)
-                throw inapplicableMethodException.setMessage("no.conforming.assignment.exists",
-                        argtypes.head,
-                        formals.head);
+            Type undetFormal = infer.asUndetType(formals.head, undetvars);
+            Type capturedActual = types.capture(argtypes.head);
+            boolean works = allowBoxing ?
+                    types.isConvertible(capturedActual, undetFormal, warn) :
+                    types.isSubtypeUnchecked(capturedActual, undetFormal, warn);
+            if (!works) {
+                throw handler.argumentMismatch(false, argtypes.head, formals.head);
+            }
+            checkedArgs.append(capturedActual);
             argtypes = argtypes.tail;
             formals = formals.tail;
         }
 
-        if (formals.head != varargsFormal)
-            throw inapplicableMethodException.setMessage("arg.length.mismatch"); // not enough args
+        if (formals.head != varargsFormal) {
+            throw handler.arityMismatch(); // not enough args
+        }
 
         if (useVarargs) {
+            //note: if applicability check is triggered by most specific test,
+            //the last argument of a varargs is _not_ an array type (see JLS 15.12.2.5)
             Type elt = types.elemtype(varargsFormal);
+            Type eltUndet = infer.asUndetType(elt, undetvars);
             while (argtypes.nonEmpty()) {
-                if (!types.isConvertible(argtypes.head, elt, warn))
-                    throw inapplicableMethodException.setMessage("varargs.argument.mismatch",
-                            argtypes.head,
-                            elt);
+                Type capturedActual = types.capture(argtypes.head);
+                if (!types.isConvertible(capturedActual, eltUndet, warn)) {
+                    throw handler.argumentMismatch(true, argtypes.head, elt);
+                }
+                checkedArgs.append(capturedActual);
                 argtypes = argtypes.tail;
             }
             //check varargs element type accessibility
-            if (!isAccessible(env, elt)) {
+            if (undetvars.isEmpty() && !isAccessible(env, elt)) {
                 Symbol location = env.enclClass.sym;
-                throw inapplicableMethodException.setMessage("inaccessible.varargs.type",
-                            elt,
-                            Kinds.kindName(location),
-                            location);
+                throw handler.inaccessibleVarargs(location, elt);
             }
         }
-        return;
+        return checkedArgs.toList();
     }
     // where
         public static class InapplicableMethodException extends RuntimeException {

--- a/langtools/src/share/classes/com/sun/tools/javac/resources/compiler.properties	Wed Jan 18 18:26:36 2012 -0800
+++ b/langtools/src/share/classes/com/sun/tools/javac/resources/compiler.properties	Tue Jan 24 17:52:02 2012 +0000
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 1999, 2012, 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
@@ -1620,6 +1620,10 @@
 compiler.misc.infer.arg.length.mismatch=\
     cannot instantiate from arguments because actual and formal argument lists differ in length
 
+# 0: list of type, 1: type, 2: type
+compiler.misc.infer.varargs.argument.mismatch=\
+    no instance(s) of type variable(s) {0} exist so that argument type {1} conforms to vararg element type {2}
+
 # 0: type, 1: list of type
 compiler.misc.inferred.do.not.conform.to.bounds=\
     inferred type does not conform to declared bound(s)\n\

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/diags/examples/InferVarargsArgumentMismatch.java	Tue Jan 24 17:52:02 2012 +0000
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2012, 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.
+ *
+ * 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.
+ */
+
+// key: compiler.err.cant.apply.symbol.1
+// key: compiler.misc.infer.varargs.argument.mismatch
+
+class InferVarargsArgumentMismatch {
+    <X> void m(X x1, String... xs) {}
+    { this.m("", 1); }
+}