8021567: Javac doesn't report \"java: reference to method is ambiguous\" any more

Javac incorrectly forgets about constant folding results within lambdas

Reviewed-by: jjg, vromero

langtools/src/share/classes/com/sun/tools/javac/code/Type.java

@@ -1525,7 +1525,7 @@ public abstract class Type implements TypeMirror {
         }
 
         protected void addBound(InferenceBound ib, Type bound, Types types, boolean update) {
-            Type bound2 = toTypeVarMap.apply(bound);
+            Type bound2 = toTypeVarMap.apply(bound).baseType();
             List<Type> prevBounds = bounds.get(ib);
             for (Type b : prevBounds) {
                 //check for redundancy - use strict version of isSameType on tvars

langtools/src/share/classes/com/sun/tools/javac/comp/Attr.java

@@ -2395,7 +2395,7 @@ public class Attr extends JCTree.Visitor {
 
             ResultInfo bodyResultInfo = lambdaType.getReturnType() == Type.recoveryType ?
                 recoveryInfo :
-                new LambdaResultInfo(lambdaType.getReturnType(), funcContext);
+                new ResultInfo(VAL, lambdaType.getReturnType(), funcContext);
             localEnv.info.returnResult = bodyResultInfo;
 
             Log.DeferredDiagnosticHandler lambdaDeferredHandler = new Log.DeferredDiagnosticHandler(log);
@@ -2602,28 +2602,6 @@ public class Attr extends JCTree.Visitor {
             }
         }
 
-        class LambdaResultInfo extends ResultInfo {
-
-            LambdaResultInfo(Type pt, CheckContext checkContext) {
-                super(VAL, pt, checkContext);
-            }
-
-            @Override
-            protected Type check(DiagnosticPosition pos, Type found) {
-                return super.check(pos, found.baseType());
-            }
-
-            @Override
-            protected ResultInfo dup(CheckContext newContext) {
-                return new LambdaResultInfo(pt, newContext);
-            }
-
-            @Override
-            protected ResultInfo dup(Type newPt) {
-                return new LambdaResultInfo(newPt, checkContext);
-            }
-        }
-
         /**
         * Lambda compatibility. Check that given return types, thrown types, parameter types
         * are compatible with the expected functional interface descriptor. This means that:

langtools/test/tools/javac/lambda/8021567/T8021567.java

@@ -0,0 +1,26 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 8021567
+ * @summary Javac doesn't report "java: reference to method is ambiguous" any more
+ * @compile/fail/ref=T8021567.out -XDrawDiagnostics T8021567.java
+ */
+
+class T8021567 {
+
+    interface I_int { int m(); }
+
+    interface I_char { char m(); }
+
+    interface I_byte { byte m(); }
+
+    void m(I_byte b) { }
+    void m(I_char b) { }
+    void m(I_int b) { }
+
+    void test() {
+        m(() -> 1); //ambiguous
+        m(() -> 256); //ok - only method(I_int) applicable
+        m(() -> { int i = 1; return i; }); //ok - only method(I_int) applicable
+        m(() -> { int i = 256; return i; }); //ok - only method(I_int) applicable
+    }
+}

langtools/test/tools/javac/lambda/8021567/T8021567.out

@@ -0,0 +1,2 @@
+T8021567.java:21:9: compiler.err.ref.ambiguous: m, kindname.method, m(T8021567.I_byte), T8021567, kindname.method, m(T8021567.I_char), T8021567
+1 error

langtools/test/tools/javac/lambda/8021567/T8021567b.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2013, 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 8021567
+ * @summary Javac doesn't report "java: reference to method is ambiguous" any more
+ */
+
+public class T8021567b {
+
+    interface SAM {
+        int m();
+    }
+
+    public static void main(String argv[]) {
+        test();
+    }
+
+    static boolean test() {
+        final int i = 0;
+        SAM s = () -> i;
+        return (s.m() == 0);
+    }
+}