7123100: javac fails with java.lang.StackOverflowError

Summary: Inference of under-constrained type-variables creates erroneous recursive wildcard types
Reviewed-by: jjg

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

 /*
- * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 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
@@ -332,25 +332,29 @@ public class Infer {
             //replace uninferred type-vars
             targs = types.subst(targs,
                     that.tvars,
-                    instaniateAsUninferredVars(undetvars, that.tvars));
+                    instantiateAsUninferredVars(undetvars, that.tvars));
         }
         return chk.checkType(warn.pos(), that.inst(targs, types), to);
     }
     //where
-    private List<Type> instaniateAsUninferredVars(List<Type> undetvars, List<Type> tvars) {
+    private List<Type> instantiateAsUninferredVars(List<Type> undetvars, List<Type> tvars) {
+        Assert.check(undetvars.length() == tvars.length());
         ListBuffer<Type> new_targs = ListBuffer.lb();
-        //step 1 - create syntethic captured vars
+        //step 1 - create synthetic captured vars
         for (Type t : undetvars) {
             UndetVar uv = (UndetVar)t;
             Type newArg = new CapturedType(t.tsym.name, t.tsym, uv.inst, syms.botType, null);
             new_targs = new_targs.append(newArg);
         }
         //step 2 - replace synthetic vars in their bounds
+        List<Type> formals = tvars;
         for (Type t : new_targs.toList()) {
             CapturedType ct = (CapturedType)t;
             ct.bound = types.subst(ct.bound, tvars, new_targs.toList());
-            WildcardType wt = new WildcardType(ct.bound, BoundKind.EXTENDS, syms.boundClass);
+            WildcardType wt = new WildcardType(syms.objectType, BoundKind.UNBOUND, syms.boundClass);
+            wt.bound = (TypeVar)formals.head;
             ct.wildcard = wt;
+            formals = formals.tail;
         }
         return new_targs.toList();
     }

test/tools/javac/cast/7123100/T7123100a.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug     7123100
+ * @summary javac fails with java.lang.StackOverflowError
+ * @compile/fail/ref=T7123100a.out -Werror -Xlint:unchecked -XDrawDiagnostics T7123100a.java
+ */
+
+class T7123100a {
+    <E extends Enum<E>> E m() {
+        return null;
+    }
+
+    <Z> void test() {
+        Z z = (Z)m();
+    }
+}

test/tools/javac/cast/7123100/T7123100a.out

+T7123100a.java:14:19: compiler.warn.prob.found.req: (compiler.misc.unchecked.cast.to.type), compiler.misc.type.captureof: 1, ?, Z
+- compiler.err.warnings.and.werror
+1 error
+1 warning

test/tools/javac/cast/7123100/T7123100b.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug     7123100
+ * @summary javac fails with java.lang.StackOverflowError
+ * @compile/fail/ref=T7123100b.out -Werror -Xlint:unchecked -XDrawDiagnostics T7123100b.java
+ */
+
+class T7123100b {
+    <Z> void test(Enum<?> e) {
+        Z z = (Z)e;
+    }
+}

test/tools/javac/cast/7123100/T7123100b.out

+T7123100b.java:10:18: compiler.warn.prob.found.req: (compiler.misc.unchecked.cast.to.type), java.lang.Enum<compiler.misc.type.captureof: 1, ?>, Z
+- compiler.err.warnings.and.werror
+1 error
+1 warning

test/tools/javac/cast/7123100/T7123100c.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug     7123100
+ * @summary javac fails with java.lang.StackOverflowError
+ * @compile/fail/ref=T7123100c.out -Werror -Xlint:unchecked -XDrawDiagnostics T7123100c.java
+ */
+
+class T7123100c {
+    <E> E m(E e) {
+        return null;
+    }
+
+    <Z> void test(Enum<?> e) {
+        Z z = (Z)m(e);
+    }
+}

test/tools/javac/cast/7123100/T7123100c.out

+T7123100c.java:14:19: compiler.warn.prob.found.req: (compiler.misc.unchecked.cast.to.type), java.lang.Enum<compiler.misc.type.captureof: 1, ?>, Z
+- compiler.err.warnings.and.werror
+1 error
+1 warning

test/tools/javac/cast/7123100/T7123100d.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug     7123100
+ * @summary javac fails with java.lang.StackOverflowError
+ * @compile/fail/ref=T7123100d.out -Werror -Xlint:unchecked -XDrawDiagnostics T7123100d.java
+ */
+
+class T7123100d {
+    <E extends Enum<E>> E m(Enum<E> e) {
+        return null;
+    }
+
+    <Z> void test(Enum<?> e) {
+        Z z = (Z)m(e);
+    }
+}

test/tools/javac/cast/7123100/T7123100d.out

+T7123100d.java:14:19: compiler.warn.prob.found.req: (compiler.misc.unchecked.cast.to.type), compiler.misc.type.captureof: 1, ?, Z
+- compiler.err.warnings.and.werror
+1 error
+1 warning