Fix crash in dartc when given cyclic type variable bounds.

tests/language/src/CyclicTypeVariableTest.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Tests cyclic reference to type variables in type expressions
+
+typedef void funcType<T 
+extends T /// 01: static type error
+>(T arg);

[gbracha, 2012/01/11 23:04:34]

We don't have generic functions (or even factories) so this example is
syntactically illegal.

[mmendez, 2012/01/12 15:29:50]

Unless there is some other countering clause, I think that this is legal per the
grammar in section 13.1 of v0.06 of the spec.

functionTypeAlias:
typedef functionPre
x typeParameters? formalParameterList ';'
;



On 2012/01/11 23:04:34, gbracha wrote:

+
+
+interface A<S 

[mmendez, 2012/01/12 15:29:50]

This should be a warning per the spec.

[zundel, 2012/01/12 15:33:59]

Yes.  the 'static type error'  is at the warning level and does not stop the
compile.

+extends S /// 02: static type error
+> {
+  S field;
+}
+
+interface B<U
+extends List<U> /// 03: static type error

[gbracha, 2012/01/11 23:04:34]

This should be perfectly legal.

[zundel, 2012/01/12 12:53:55]

How could you make a legal substitution into this? 

new B<int>  // doesn't extent List<int>
new B<List<int>>// doesn't extent List<List<int>>

+> {
+  U field;
+}
+
+class C<V
+extends V /// 04: static type error
+> implements A<V> {
+  V field;
+}
+
+class D<W
+extends List<W> /// 05: static type error

[gbracha, 2012/01/11 23:04:34]

Again, this is perfectly valid.

+> implements B<W>{
+  W field;
+}
+
+
+class E<X
+extends funcType<X> /// 06: static type error

[gbracha, 2012/01/11 23:04:34]

Since functType isn't valid, the point is moot, but this would otherwise be
legal.

+> {
+  X field;
+}
+
+main() {
+  new C<List<Object>>();
+  new D<List<Object>>();
+  new E<funcType<Object>>();
+  funcType<Object> val = null;
+}