Fix 5024 - diagnostic on unresolved catch types, added test case

lib/compiler/implementation/resolver.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.
 
 interface TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   DartType getType(TypeAnnotation annotation);
   bool isParameterChecked(Element element);
 }
@@ skipping 1918 matching lines @@
           error(modifier, MessageKind.PARAMETER_WITH_MODIFIER_IN_CATCH);
         }
         TypeAnnotation type = declaration.type;
         if (type !== null) {
           error(type, MessageKind.PARAMETER_WITH_TYPE_IN_CATCH);
         }
       }
     }
 
     Scope blockScope = new BlockScope(scope);
+    var wasTypeRequired = typeRequired;
+    typeRequired = true;
     doInCheckContext(() => visitIn(node.type, blockScope));
+    typeRequired = wasTypeRequired;
     visitIn(node.formals, blockScope);
     visitIn(node.block, blockScope);
   }
 
   visitTypedef(Typedef node) {
     unimplemented(node, 'typedef');
   }
 }
 
 class TypeDefinitionVisitor extends CommonResolverVisitor<DartType> {
@@ skipping 798 matching lines @@
 
   Element localLookup(SourceString name) => library.find(name);
   Element lookup(SourceString name) => localLookup(name);
   Element lexicalLookup(SourceString name) => localLookup(name);
 
   Element add(Element newElement) {
     throw "Cannot add an element in the top scope";
   }
   String toString() => '$element';
 }