Use entities in the TypeSystem interface.

pkg/compiler/lib/src/inferrer/builder.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 simple_types_inferrer;
 
 import '../closure.dart' show ClosureRepresentationInfo;
 import '../common.dart';
 import '../common/names.dart' show Identifiers, Selectors;
 import '../compiler.dart' show Compiler;
@@ skipping 726 matching lines @@
   TypeInformation visitThrow(ast.Throw node) {
     node.visitChildren(this);
     locals.seenReturnOrThrow = true;
     return types.nonNullEmpty();
   }
 
   TypeInformation visitCatchBlock(ast.CatchBlock node) {
     ast.Node exception = node.exception;
     if (exception != null) {
       ResolutionDartType type = elements.getType(node.type);
-      TypeInformation mask =
-          type == null || type.treatAsDynamic || type.isTypeVariable
-              ? types.dynamicType
-              : types.nonNullSubtype(type.element);
+      TypeInformation mask;
+      if (type == null || type.treatAsDynamic || type.isTypeVariable) {
+        mask = types.dynamicType;
+      } else {
+        ResolutionInterfaceType interfaceType = type;
+        mask = types.nonNullSubtype(interfaceType.element);
+      }
       locals.update(elements[exception], mask, node);
     }
     ast.Node trace = node.trace;
     if (trace != null) {
       locals.update(elements[trace], types.dynamicType, node);
     }
     visit(node.block);
     return null;
   }
 
@@ skipping 2181 matching lines @@
     Selector moveNextSelector = Selectors.moveNext;
     TypeMask moveNextMask = memberData.typeOfIteratorMoveNext(node);
 
     TypeInformation iteratorType = handleDynamicSend(node, iteratorSelector,
         iteratorMask, expressionType, new ArgumentsTypes.empty());
 
     return handleForInLoop(node, iteratorType, currentSelector, currentMask,
         moveNextSelector, moveNextMask);
   }
 }