7062745: Regression: difference in overload resolution when two methods are maximally specific

Summary: Fix most specific when two methods are maximally specific and only one has non-raw return type
Reviewed-by: jjg, dlsmith

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

@@ -767,16 +767,13 @@ public class Resolve {
                                        m2.erasure(types).getParameterTypes()))
                     return ambiguityError(m1, m2);
                 // both abstract, neither overridden; merge throws clause and result type
-                Symbol mostSpecific;
-                if (types.returnTypeSubstitutable(mt1, mt2))
-                    mostSpecific = m1;
-                else if (types.returnTypeSubstitutable(mt2, mt1))
-                    mostSpecific = m2;
-                else {
+                Type mst = mostSpecificReturnType(mt1, mt2);
+                if (mst == null) {
                     // Theoretically, this can't happen, but it is possible
                     // due to error recovery or mixing incompatible class files
                     return ambiguityError(m1, m2);
                 }
+                Symbol mostSpecific = mst == mt1 ? m1 : m2;
                 List<Type> allThrown = chk.intersect(mt1.getThrownTypes(), mt2.getThrownTypes());
                 Type newSig = types.createMethodTypeWithThrown(mostSpecific.type, allThrown);
                 MethodSymbol result = new MethodSymbol(
@@ -859,6 +856,28 @@ public class Resolve {
         }
     }
     //where
+    Type mostSpecificReturnType(Type mt1, Type mt2) {
+        Type rt1 = mt1.getReturnType();
+        Type rt2 = mt2.getReturnType();
+
+        if (mt1.tag == FORALL && mt2.tag == FORALL) {
+            //if both are generic methods, adjust return type ahead of subtyping check
+            rt1 = types.subst(rt1, mt1.getTypeArguments(), mt2.getTypeArguments());
+        }
+        //first use subtyping, then return type substitutability
+        if (types.isSubtype(rt1, rt2)) {
+            return mt1;
+        } else if (types.isSubtype(rt2, rt1)) {
+            return mt2;
+        } else if (types.returnTypeSubstitutable(mt1, mt2)) {
+            return mt1;
+        } else if (types.returnTypeSubstitutable(mt2, mt1)) {
+            return mt2;
+        } else {
+            return null;
+        }
+    }
+    //where
     Symbol ambiguityError(Symbol m1, Symbol m2) {
         if (((m1.flags() | m2.flags()) & CLASH) != 0) {
             return (m1.flags() & CLASH) == 0 ? m1 : m2;

test/tools/javac/generics/rawOverride/7062745/GenericOverrideTest.java

+/*
+ * Copyright (c) 2011, 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 7062745
+ * @summary  Regression: difference in overload resolution when two methods are maximally specific
+ */
+
+import com.sun.source.util.JavacTask;
+import java.net.URI;
+import java.util.Arrays;
+import javax.tools.Diagnostic;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.StandardJavaFileManager;
+import javax.tools.ToolProvider;
+
+public class GenericOverrideTest {
+
+    static int checkCount = 0;
+
+    enum SignatureKind {
+        NON_GENERIC(""),
+        GENERIC("<X>");
+
+        String paramStr;
+
+        private SignatureKind(String paramStr) {
+            this.paramStr = paramStr;
+        }
+    }
+
+    enum ReturnTypeKind {
+        LIST("List"),
+        ARRAYLIST("ArrayList");
+
+        String retStr;
+
+        private ReturnTypeKind(String retStr) {
+            this.retStr = retStr;
+        }
+
+        boolean moreSpecificThan(ReturnTypeKind that) {
+            switch (this) {
+                case LIST:
+                    return that == this;
+                case ARRAYLIST:
+                    return that == LIST || that == ARRAYLIST;
+                default: throw new AssertionError("Unexpected ret kind: " + this);
+            }
+        }
+    }
+
+    enum TypeArgumentKind {
+        NONE(""),
+        UNBOUND("<?>"),
+        INTEGER("<Number>"),
+        NUMBER("<Integer>"),
+        TYPEVAR("<X>");
+
+        String typeargStr;
+
+        private TypeArgumentKind(String typeargStr) {
+            this.typeargStr = typeargStr;
+        }
+
+        boolean compatibleWith(SignatureKind sig) {
+            switch (this) {
+                case TYPEVAR: return sig != SignatureKind.NON_GENERIC;
+                default: return true;
+            }
+        }
+
+        boolean moreSpecificThan(TypeArgumentKind that, boolean strict) {
+            switch (this) {
+                case NONE:
+                    return that == this || !strict;
+                case UNBOUND:
+                    return that == this || that == NONE;
+                case INTEGER:
+                case NUMBER:
+                case TYPEVAR:
+                    return that == this || that == NONE || that == UNBOUND;
+                default: throw new AssertionError("Unexpected typearg kind: " + this);
+            }
+        }
+
+        boolean assignableTo(TypeArgumentKind that, SignatureKind sig) {
+            switch (this) {
+                case NONE:
+                    //this case needs to workaround to javac's impl of 15.12.2.8 being too strict
+                    //ideally should be just 'return true' (see 7067746)
+                    return sig == SignatureKind.NON_GENERIC || that == NONE;
+                case UNBOUND:
+                    return that == this || that == NONE;
+                case INTEGER:
+                case NUMBER:
+                    return that == this || that == NONE || that == UNBOUND;
+                case TYPEVAR:
+                    return true;
+                default: throw new AssertionError("Unexpected typearg kind: " + this);
+            }
+        }
+    }
+
+    public static void main(String... args) throws Exception {
+
+        //create default shared JavaCompiler - reused across multiple compilations
+        JavaCompiler comp = ToolProvider.getSystemJavaCompiler();
+        StandardJavaFileManager fm = comp.getStandardFileManager(null, null, null);
+
+        for (SignatureKind sig1 : SignatureKind.values()) {
+            for (ReturnTypeKind rt1 : ReturnTypeKind.values()) {
+                for (TypeArgumentKind ta1 : TypeArgumentKind.values()) {
+                    if (!ta1.compatibleWith(sig1)) continue;
+                    for (SignatureKind sig2 : SignatureKind.values()) {
+                        for (ReturnTypeKind rt2 : ReturnTypeKind.values()) {
+                            for (TypeArgumentKind ta2 : TypeArgumentKind.values()) {
+                                if (!ta2.compatibleWith(sig2)) continue;
+                                for (ReturnTypeKind rt3 : ReturnTypeKind.values()) {
+                                    for (TypeArgumentKind ta3 : TypeArgumentKind.values()) {
+                                        if (!ta3.compatibleWith(SignatureKind.NON_GENERIC)) continue;
+                                        new GenericOverrideTest(sig1, rt1, ta1, sig2, rt2, ta2, rt3, ta3).run(comp, fm);
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        System.out.println("Total check executed: " + checkCount);
+    }
+
+    SignatureKind sig1, sig2;
+    ReturnTypeKind rt1, rt2, rt3;
+    TypeArgumentKind ta1, ta2, ta3;
+    JavaSource source;
+    DiagnosticChecker diagChecker;
+
+    GenericOverrideTest(SignatureKind sig1, ReturnTypeKind rt1, TypeArgumentKind ta1,
+            SignatureKind sig2, ReturnTypeKind rt2, TypeArgumentKind ta2, ReturnTypeKind rt3, TypeArgumentKind ta3) {
+        this.sig1 = sig1;
+        this.sig2 = sig2;
+        this.rt1 = rt1;
+        this.rt2 = rt2;
+        this.rt3 = rt3;
+        this.ta1 = ta1;
+        this.ta2 = ta2;
+        this.ta3 = ta3;
+        this.source = new JavaSource();
+        this.diagChecker = new DiagnosticChecker();
+    }
+
+    class JavaSource extends SimpleJavaFileObject {
+
+        String template = "import java.util.*;\n" +
+                          "interface A { #S1 #R1#TA1 m(); }\n" +
+                          "interface B { #S2 #R2#TA2 m(); }\n" +
+                          "interface AB extends A, B {}\n" +
+                          "class Test {\n" +
+                          "  void test(AB ab) { #R3#TA3 n = ab.m(); }\n" +
+                          "}";
+
+        String source;
+
+        public JavaSource() {
+            super(URI.create("myfo:/Test.java"), JavaFileObject.Kind.SOURCE);
+            source = template.replace("#S1", sig1.paramStr).
+                    replace("#S2", sig2.paramStr).
+                    replace("#R1", rt1.retStr).
+                    replace("#R2", rt2.retStr).
+                    replace("#R3", rt3.retStr).
+                    replace("#TA1", ta1.typeargStr).
+                    replace("#TA2", ta2.typeargStr).
+                    replace("#TA3", ta3.typeargStr);
+        }
+
+        @Override
+        public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+            return source;
+        }
+    }
+
+    void run(JavaCompiler tool, StandardJavaFileManager fm) throws Exception {
+        JavacTask ct = (JavacTask)tool.getTask(null, fm, diagChecker,
+                null, null, Arrays.asList(source));
+        try {
+            ct.analyze();
+        } catch (Throwable ex) {
+            throw new AssertionError("Error thron when compiling the following code:\n" + source.getCharContent(true));
+        }
+        check();
+    }
+
+    void check() {
+        checkCount++;
+
+        boolean errorExpected = false;
+        int mostSpecific = 0;
+
+        //first check that either |R1| <: |R2| or |R2| <: |R1|
+        if (rt1 != rt2) {
+            if (!rt1.moreSpecificThan(rt2) &&
+                    !rt2.moreSpecificThan(rt1)) {
+                errorExpected = true;
+            } else {
+                mostSpecific = rt1.moreSpecificThan(rt2) ? 1 : 2;
+            }
+        }
+
+        //check that either TA1 <= TA2 or TA2 <= TA1 (unless most specific return found above is raw)
+        if (!errorExpected) {
+            if (ta1 != ta2) {
+                boolean useStrictCheck = ta1.moreSpecificThan(ta2, true) || ta2.moreSpecificThan(ta1, true);
+                if (!ta1.moreSpecificThan(ta2, useStrictCheck) &&
+                        !ta2.moreSpecificThan(ta1, useStrictCheck)) {
+                    errorExpected = true;
+                } else {
+                    int mostSpecific2 = ta1.moreSpecificThan(ta2, useStrictCheck) ? 1 : 2;
+                    if (mostSpecific != 0 && mostSpecific2 != mostSpecific) {
+                        errorExpected = mostSpecific == 1 ? ta1 != TypeArgumentKind.NONE : ta2 != TypeArgumentKind.NONE;
+                    } else {
+                        mostSpecific = mostSpecific2;
+                    }
+                }
+            } else if (mostSpecific == 0) {
+                //when no signature is better than the other, an arbitrary choice
+                //must be made - javac always picks the second signature
+                mostSpecific = 2;
+            }
+        }
+
+        //finally, check that most specific return type is compatible with expected type
+        if (!errorExpected) {
+            ReturnTypeKind msrt = mostSpecific == 1 ? rt1 : rt2;
+            TypeArgumentKind msta = mostSpecific == 1 ? ta1 : ta2;
+            SignatureKind mssig = mostSpecific == 1 ? sig1 : sig2;
+
+            if (!msrt.moreSpecificThan(rt3) ||
+                    !msta.assignableTo(ta3, mssig)) {
+                errorExpected = true;
+            }
+        }
+
+        if (errorExpected != diagChecker.errorFound) {
+            throw new Error("invalid diagnostics for source:\n" +
+                source.getCharContent(true) +
+                "\nFound error: " + diagChecker.errorFound +
+                "\nExpected error: " + errorExpected);
+        }
+    }
+
+    static class DiagnosticChecker implements javax.tools.DiagnosticListener<JavaFileObject> {
+
+        boolean errorFound;
+
+        public void report(Diagnostic<? extends JavaFileObject> diagnostic) {
+            if (diagnostic.getKind() == Diagnostic.Kind.ERROR) {
+                errorFound = true;
+            }
+        }
+    }
+}

test/tools/javac/generics/rawOverride/7062745/T7062745neg.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug     7062745
+ * @summary  Regression: difference in overload resolution when two methods are maximally specific
+ * @compile/fail/ref=T7062745neg.out -XDrawDiagnostics T7062745neg.java
+ */
+
+import java.util.*;
+
+class T7062745neg {
+    interface A { List<Number> getList(); }
+    interface B { ArrayList getList(); }
+    interface AB extends A, B {}
+
+    void test(AB ab) {
+        Number n = ab.getList().get(1);
+    }
+}

test/tools/javac/generics/rawOverride/7062745/T7062745neg.out

+T7062745neg.java:16:36: compiler.err.prob.found.req: (compiler.misc.incompatible.types), java.lang.Object, java.lang.Number
+1 error

test/tools/javac/generics/rawOverride/7062745/T7062745pos.java

+/*
+ * Copyright (c) 2011, 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 7062745
+ * @summary  Regression: difference in overload resolution when two methods are maximally specific
+ *
+ * @compile T7062745pos.java
+ */
+
+import java.util.*;
+
+class T7062745pos {
+    interface A { List<Number> getList(); }
+    interface B { List getList(); }
+    interface AB extends A, B {}
+
+    void test(AB ab) {
+        Number n = ab.getList().get(1);
+    }
+}