Support general handling of type variables by substituting types into the current context.

sdk/lib/_internal/compiler/implementation/inferrer/inferrer_visitor.dart

 // Copyright (c) 2013, 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.
 
 library inferrer_visitor;
 
 import '../dart2jslib.dart' hide Selector, TypedSelector;
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../tree/tree.dart';
@@ skipping 1063 matching lines @@
   T visitThrow(Throw node) {
     node.visitChildren(this);
     locals.seenReturnOrThrow = true;
     return types.nonNullEmpty();
   }
 
   T visitCatchBlock(CatchBlock node) {
     Node exception = node.exception;
     if (exception != null) {
       DartType type = elements.getType(node.type);
-      T mask = type == null || type.treatAsDynamic
+      T mask = type == null ||
+               type.treatAsDynamic ||
+               type.kind == TypeKind.TYPE_VARIABLE
           ? types.dynamicType
           : types.nonNullSubtype(type.element);
       locals.update(elements[exception], mask, node);
     }
     Node trace = node.trace;
     if (trace != null) {
       locals.update(elements[trace], types.dynamicType, node);
     }
     visit(node.block);
     return null;
@@ skipping 119 matching lines @@
     return type;
   }
 
   T visitCascade(Cascade node) {
     // Ignore the result of the cascade send and return the type of the cascade
     // receiver.
     visit(node.expression);
     return cascadeReceiverStack.removeLast();
   }
 }