diff -r 9bfb0e6fd526 -r 493ecc8111ba src/share/classes/com/sun/tools/javac/comp/Infer.java
--- a/src/share/classes/com/sun/tools/javac/comp/Infer.java	Wed Oct 13 17:52:29 2010 -0700
+++ b/src/share/classes/com/sun/tools/javac/comp/Infer.java	Mon Oct 18 19:14:36 2010 +0100
@@ -553,12 +553,24 @@
             //the enclosing tree E, as follows: if E is a cast, then use the
             //target type of the cast expression as a return type; if E is an
             //expression statement, the return type is 'void' - otherwise the
-            //return type is simply 'Object'.
-            switch (env.outer.tree.getTag()) {
+            //return type is simply 'Object'. A correctness check ensures that
+            //env.next refers to the lexically enclosing environment in which
+            //the polymorphic signature call environment is nested.
+
+            switch (env.next.tree.getTag()) {
                 case JCTree.TYPECAST:
-                    restype = ((JCTypeCast)env.outer.tree).clazz.type; break;
+                    JCTypeCast castTree = (JCTypeCast)env.next.tree;
+                    restype = (castTree.expr == env.tree) ?
+                        castTree.clazz.type :
+                        syms.objectType;
+                    break;
                 case JCTree.EXEC:
-                    restype = syms.voidType; break;
+                    JCTree.JCExpressionStatement execTree =
+                            (JCTree.JCExpressionStatement)env.next.tree;
+                    restype = (execTree.expr == env.tree) ?
+                        syms.voidType :
+                        syms.objectType;
+                    break;
                 default:
                     restype = syms.objectType;
             }