6999067: cast for invokeExact call gets redundant cast to <type> warnings

Summary: Xlint:cast should not report cast used in order to specify target type in polymorphic signature calls
Reviewed-by: jjg

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

@@ -1371,11 +1371,24 @@ public class Flow extends TreeScanner {
         if (!tree.type.isErroneous()
             && lint.isEnabled(Lint.LintCategory.CAST)
             && types.isSameType(tree.expr.type, tree.clazz.type)
-            && !(ignoreAnnotatedCasts && containsTypeAnnotation(tree.clazz))) {
+            && !(ignoreAnnotatedCasts && containsTypeAnnotation(tree.clazz))
+            && !is292targetTypeCast(tree)) {
             log.warning(Lint.LintCategory.CAST,
                     tree.pos(), "redundant.cast", tree.expr.type);
         }
     }
+    //where
+        private boolean is292targetTypeCast(JCTypeCast tree) {
+            boolean is292targetTypeCast = false;
+            if (tree.expr.getTag() == JCTree.APPLY) {
+                JCMethodInvocation apply = (JCMethodInvocation)tree.expr;
+                Symbol sym = TreeInfo.symbol(apply.meth);
+                is292targetTypeCast = sym != null &&
+                    sym.kind == MTH &&
+                    (sym.flags() & POLYMORPHIC_SIGNATURE) != 0;
+            }
+            return is292targetTypeCast;
+        }
 
     public void visitTopLevel(JCCompilationUnit tree) {
         // Do nothing for TopLevel since each class is visited individually

test/tools/javac/meth/XlintWarn.java

+/*
+ * Copyright (c) 2008, 2010, 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 6999067
+ * @summary cast for invokeExact call gets redundant cast to <type> warnings
+ * @author mcimadamore
+ *
+ * @compile -Werror -Xlint:cast XlintWarn.java
+ */
+
+import java.dyn.*;
+
+class XlintWarn {
+    void test(MethodHandle mh) throws Throwable {
+        int i1 = (int)mh.invoke();
+        int i2 = (int)mh.invokeExact();
+        int i3 = (int)mh.invokeVarargs();
+        int i4 = (int)InvokeDynamic.test();
+    }
+}