8041663: Sensitive dependence on location of nested interface

Summary: Adding a method among ambiguous candidates only if it is more specific than some of the existing candidates.
Reviewed-by: dlsmith, vromero

src/share/classes/com/sun/tools/javac/comp/Resolve.java

@@ -1524,14 +1524,22 @@ public class Resolve {
             if (m2SignatureMoreSpecific) return m2;
             return ambiguityError(m1, m2);
         case AMBIGUOUS:
-            //check if m1 is more specific than all ambiguous methods in m2
+            //compare m1 to ambiguous methods in m2
             AmbiguityError e = (AmbiguityError)m2.baseSymbol();
+            boolean m1MoreSpecificThanAnyAmbiguous = true;
+            boolean allAmbiguousMoreSpecificThanM1 = true;
             for (Symbol s : e.ambiguousSyms) {
-                if (mostSpecific(argtypes, m1, s, env, site, allowBoxing, useVarargs) != m1) {
-                    return e.addAmbiguousSymbol(m1);
-                }
+                Symbol moreSpecific = mostSpecific(argtypes, m1, s, env, site, allowBoxing, useVarargs);
+                m1MoreSpecificThanAnyAmbiguous &= moreSpecific == m1;
+                allAmbiguousMoreSpecificThanM1 &= moreSpecific == s;
             }
-            return m1;
+            if (m1MoreSpecificThanAnyAmbiguous)
+                return m1;
+            //if m1 is more specific than some ambiguous methods, but other ambiguous methods are
+            //more specific than m1, add it as a new ambiguous method:
+            if (!allAmbiguousMoreSpecificThanM1)
+                e.addAmbiguousSymbol(m1);
+            return e;
         default:
             throw new AssertionError();
         }

test/tools/javac/resolve/AmbiguityErrorTest.java

+/*
+ * Copyright (c) 2014, 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.
+ */
+
+/**
+ * @test
+ * @bug 8041663
+ */
+
+public class AmbiguityErrorTest {
+
+    public interface A { }
+
+    public interface B extends A { }
+
+    public interface C {
+        A m(B strategy);
+    }
+
+    public interface D {
+        A m(A strategy);
+        A m(B strategy);
+    }
+
+    public interface T1 extends C, D { }
+    public interface T2 extends D, C { }
+
+    int count;
+
+    class T1Impl implements T1, T2 {
+        public A m(B strategy) {
+            count++;
+            return null;
+        }
+        public A m(A strategy) {
+            throw new AssertionError("Should not get here.");
+        }
+    }
+
+    public static void main(String... args) {
+        new AmbiguityErrorTest().test();
+    }
+
+    void test() {
+        T1 t1 = new T1Impl();
+        T2 t2 = new T1Impl();
+        final B b = new B() { };
+        t1.m(b);
+        t2.m(b);
+
+        if (count != 2) {
+            throw new IllegalStateException("Did not call the methods properly");
+        }
+    }
+
+}