Fix argument test for the captured parameter of an outer function (issue 8007).

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 7692 matching lines @@
 // or of one of its enclosing functions.
 // Make sure not to capture the formal parameter, since it is not accessed.
 bool Parser::IsFormalParameter(const String& ident,
                                Function* owner_function,
                                LocalScope** owner_scope,
                                intptr_t* local_index) {
   if (current_block_ == NULL) {
     return false;
   }
   if (ident.Equals(Symbols::This())) {
-    // 'this' is not a formal parameter.
+    // 'this' is not a formal parameter that can be tested with '?this'.
     return false;
   }
   // Since an argument definition test does not use the value of the formal
   // parameter, there is no reason to capture it.
   const bool kTestOnly = true;  // No capturing.
   LocalVariable* local =
       current_block_->scope->LookupVariable(ident, kTestOnly);
-  if (local == NULL) {
-    if (!current_function().IsLocalFunction()) {
+  if ((local == NULL) ||
+      (local->owner()->HasContextLevel() &&
+       (local->owner()->context_level() < 1))) {
+    if ((local == NULL) && !current_function().IsLocalFunction()) {
       // We are not generating code for a local function, so all locals,
       // captured or not, are in scope. However, 'ident' was not found, so it
       // does not exist.
       return false;
     }
-    // The formal parameter may belong to an enclosing function and may not have
+    // The formal parameter belongs to an enclosing function and may not have
     // been captured, so it was not included in the context scope and it cannot
     // be found by LookupVariable.
+    ASSERT((local == NULL) || local->is_captured());
     // 'ident' necessarily refers to the formal parameter of one of the
     // enclosing functions, or a compile error would have prevented the
     // outermost enclosing function to be executed and we would not be compiling
     // this local function.
     // Therefore, look for ident directly in the formal parameter lists of the
     // enclosing functions.
     // There is no need to return the owner_scope, since the caller will not
     // create the saved_arguments_descriptor variable, which already exists.
     Function& function = Function::Handle(innermost_function().raw());
     String& param_name = String::Handle();
@@ skipping 1956 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart