Handle malformed types in catch-on.

sdk/lib/_internal/compiler/implementation/ssa/builder.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/builder.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/builder.dart b/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
index 67085fdb8a719521baf050b245c134aff2505a0b..0d2d98e1fc7f082e38453da1976076c23c0a2d14 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
@@ -4451,12 +4451,18 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
         if (catchBlock.onKeyword != null) {
           DartType type = elements.getType(catchBlock.type);
           if (type == null) {
-            compiler.cancel('On with unresolved type',
+            compiler.cancel('On with no type',

[ngeoffray, 2013/02/05 09:43:46]

Fits in one line?

[Johnni Winther, 2013/02/18 14:51:43]

Done.

                             node: catchBlock.type);
           }
-          HInstruction condition =
-              new HIs(type, <HInstruction>[unwrappedException]);
-          push(condition);
+          if (type.isMalformed) {
+            HInstruction condition =
+                graph.addConstantBool(false, constantSystem);

[ngeoffray, 2013/02/05 09:43:46]

Fits in one line?

[Johnni Winther, 2013/02/18 14:51:43]

:( No.

+            stack.add(condition);

[ahe, 2013/02/05 09:58:39]

Am I understanding this correctly: the specification say that using a malformed
type in a type test always returns false. It doesn't lead to an exception.

However, in checked mode, an exception often occur, but that is the implicit
type assertion as part of assignment, return, and parameter type checks.

[karlklose, 2013/02/05 10:21:45]

Shouldn't we treat any malformed type as dynamic and returning true here?

In checked mode, I think this counts as a subtype test and we have to create a
dynamic type error.

13.2: "In checked mode, it is a dynamic type error if a malformed type is used
in a subtype test. In production mode, an undeclared type is treated as an
instance of type dynamic."

+          } else {
+            HInstruction condition =
+                new HIs(type, <HInstruction>[unwrappedException]);
+            push(condition);
+          }
         }
         else {
           VariableDefinitions declaration = catchBlock.formals.nodes.head;