7126754: Generics compilation failure casting List<? extends Set...> to List<Set...>

Summary: Problems with Types.rewriteQuantifiers not preserving variance
Reviewed-by: jjg

src/share/classes/com/sun/tools/javac/code/Types.java

 /*
- * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2012, 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
@@ -3600,39 +3600,44 @@ public class Types {
 
         @Override
         public Type visitCapturedType(CapturedType t, Void s) {
-            Type bound = visitWildcardType(t.wildcard, null);
-            return (bound.contains(t)) ?
-                    erasure(bound) :
-                    bound;
+            Type w_bound = t.wildcard.type;
+            Type bound = w_bound.contains(t) ?
+                        erasure(w_bound) :
+                        visit(w_bound);
+            return rewriteAsWildcardType(visit(bound), t.wildcard.bound, t.wildcard.kind);
         }
 
         @Override
         public Type visitTypeVar(TypeVar t, Void s) {
             if (rewriteTypeVars) {
-                Type bound = high ?
-                    (t.bound.contains(t) ?
+                Type bound = t.bound.contains(t) ?
                         erasure(t.bound) :
-                        visit(t.bound)) :
-                    syms.botType;
-                return rewriteAsWildcardType(bound, t);
-            }
-            else
+                        visit(t.bound);
+                return rewriteAsWildcardType(bound, t, EXTENDS);
+            } else {
                 return t;
+            }
         }
 
         @Override
         public Type visitWildcardType(WildcardType t, Void s) {
-            Type bound = high ? t.getExtendsBound() :
-                                t.getSuperBound();
-            if (bound == null)
-            bound = high ? syms.objectType : syms.botType;
-            return rewriteAsWildcardType(visit(bound), t.bound);
-        }
-
-        private Type rewriteAsWildcardType(Type bound, TypeVar formal) {
-            return high ?
-                makeExtendsWildcard(B(bound), formal) :
-                makeSuperWildcard(B(bound), formal);
+            Type bound2 = visit(t.type);
+            return t.type == bound2 ? t : rewriteAsWildcardType(bound2, t.bound, t.kind);
+        }
+
+        private Type rewriteAsWildcardType(Type bound, TypeVar formal, BoundKind bk) {
+            switch (bk) {
+               case EXTENDS: return high ?
+                       makeExtendsWildcard(B(bound), formal) :
+                       makeExtendsWildcard(syms.objectType, formal);
+               case SUPER: return high ?
+                       makeSuperWildcard(syms.botType, formal) :
+                       makeSuperWildcard(B(bound), formal);
+               case UNBOUND: return makeExtendsWildcard(syms.objectType, formal);
+               default:
+                   Assert.error("Invalid bound kind " + bk);
+                   return null;
+            }
         }
 
         Type B(Type t) {

test/tools/javac/cast/7126754/T7126754.java

+/*
+ * @test /nodynamiccopyright/
+ * @author mcimadamore
+ * @bug     7005671
+ * @summary Generics compilation failure casting List<? extends Set...> to List<Set...>
+ * @compile/fail/ref=T7126754.out -Xlint:unchecked -Werror -XDrawDiagnostics T7126754.java
+ */
+
+import java.util.List;
+
+class T7126754 {
+    List<? extends List<? extends String>> c = null;
+    List<List<? extends String>> d = (List<List<? extends String>>)c;
+}

test/tools/javac/cast/7126754/T7126754.out

+T7126754.java:13:68: compiler.warn.prob.found.req: (compiler.misc.unchecked.cast.to.type), java.util.List<compiler.misc.type.captureof: 1, ? extends java.util.List<? extends java.lang.String>>, java.util.List<java.util.List<? extends java.lang.String>>
+- compiler.err.warnings.and.werror
+1 error
+1 warning