Clarify error message when illegally accessing 'this'

runtime/vm/parser.cc

 // 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.
 
 #include "vm/parser.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/compiler_stats.h"
@@ skipping 3924 matching lines @@
 
 AstNode* Parser::LoadReceiver(intptr_t token_pos) {
   // A nested function may access 'this', referring to the receiver of the
   // outermost enclosing function.
   // We should not be loading the receiver from a static scope.
   ASSERT(!current_function().is_static() ||
          current_function().IsInFactoryScope());
   const bool kTestOnly = false;
   LocalVariable* receiver = LookupReceiver(current_block_->scope, kTestOnly);
   if (receiver == NULL) {
-    ErrorMsg(token_pos, "illegal access to 'this'");
+    ErrorMsg(token_pos, "illegal implicit access to receiver 'this'");
   }
   return new LoadLocalNode(token_index_, *receiver);
 }
 
 
 AstNode* Parser::CallGetter(intptr_t token_index,
                             AstNode* object,
                             const String& name) {
   return new InstanceGetterNode(token_index_, object, name);
 }
@@ skipping 4200 matching lines @@
       // the identifier locally in that library (we do not include the
       // libraries imported by that library).
       primary = ResolveIdentInLibraryPrefixScope(*(qual_ident.lib_prefix),
                                                  qual_ident);
     }
     ASSERT(primary != NULL);
   } else if (CurrentToken() == Token::kTHIS) {
     const String& this_name = String::Handle(String::NewSymbol(kThisName));
     LocalVariable* local = LookupLocalScope(this_name);
     if (local == NULL) {
-      ErrorMsg("unexpected use of 'this' in primary expression");
+      ErrorMsg("receiver 'this' is not in scope");
     }
     primary = new LoadLocalNode(token_index_, *local);
     ConsumeToken();
   } else if (CurrentToken() == Token::kINTEGER) {
     const Integer& literal = Integer::ZoneHandle(CurrentIntegerLiteral());
     primary = new LiteralNode(token_index_, literal);
     ConsumeToken();
   } else if (CurrentToken() == Token::kTRUE) {
     primary = new LiteralNode(token_index_, Bool::ZoneHandle(Bool::True()));
     ConsumeToken();
@@ skipping 339 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart