Reduce usage of .enclosingElement to get enclosing class.

lib/compiler/implementation/typechecker.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.
 
 class TypeCheckerTask extends CompilerTask {
   TypeCheckerTask(Compiler compiler) : super(compiler);
   String get name() => "Type checker";
 
   static final bool LOG_FAILURES = false;
 
@@ skipping 321 matching lines @@
         element.kind === ElementKind.GENERATIVE_CONSTRUCTOR_BODY) {
       type = types.dynamicType;
       returnType = types.voidType;
     } else {
       FunctionType functionType = computeType(element);
       returnType = functionType.returnType;
       type = functionType;
     }
     Type previous = expectedReturnType;
     expectedReturnType = returnType;
-    if (element.isMember()) currentClass = element.enclosingElement;
+    if (element.isMember()) currentClass = element.getEnclosingClass();
     StatementType bodyType = analyze(node.body);
     if (returnType != types.voidType && returnType != types.dynamicType
         && bodyType != StatementType.RETURNING) {
       MessageKind kind;
       if (bodyType == StatementType.MAYBE_RETURNING) {
         kind = MessageKind.MAYBE_MISSING_RETURN;
       } else {
         kind = MessageKind.MISSING_RETURN;
       }
       reportTypeWarning(node.name, kind);
@@ skipping 421 matching lines @@
   }
 
   visitCatchBlock(CatchBlock node) {
     return unhandledStatement();
   }
 
   visitTypedef(Typedef node) {
     return unhandledStatement();
   }
 }