Remove saving/restoring of the context at function entry.

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 "lib/invocation_mirror.h"
 #include "platform/utils.h"
 #include "vm/ast_transformer.h"
 #include "vm/bootstrap.h"
@@ skipping 175 matching lines @@
   LocalScope* context_owner = NULL;  // No context needed yet.
   bool found_captured_variables = false;
   int next_free_frame_index =
       scope->AllocateVariables(first_parameter_index_,
                                num_params,
                                first_stack_local_index_,
                                scope,
                                &context_owner,
                                &found_captured_variables);
 
-  // We save the entry context for a function when...
-  //
-  //   - some variable in the function is captured by nested functions, and
-  //   - the function does not capture any variables from parent functions.
-  //
-  // We used to link to the parent context in these cases, but this
-  // had the effect of unintentionally retaining parent contexts which
-  // would never be accessed.  By breaking the context chain at this
-  // point, we allow these outer contexts to be collected.
-  if (found_captured_variables) {
-    const ContextScope& context_scope =
-        ContextScope::Handle(function().context_scope());
-    if (context_scope.IsNull() || (context_scope.num_variables() == 0)) {
-      // Allocate a local variable for saving the entry context.
-      LocalVariable* context_var =
-          new LocalVariable(function().token_pos(),
-                            Symbols::SavedEntryContextVar(),
-                            Type::ZoneHandle(Type::DynamicType()));
-      context_var->set_index(next_free_frame_index--);
-      scope->AddVariable(context_var);
-      set_saved_entry_context_var(context_var);
-    }
-  }
-
   // Frame indices are relative to the frame pointer and are decreasing.
   ASSERT(next_free_frame_index <= first_stack_local_index_);
   num_stack_locals_ = first_stack_local_index_ - next_free_frame_index;
 }
 
 
 struct CatchParamDesc {
   CatchParamDesc()
       : token_pos(0), type(NULL), name(NULL), var(NULL) { }
   intptr_t token_pos;
@@ skipping 11698 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart