Add some scope-related DCHECKs.

src/ast/variables.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_AST_VARIABLES_H_
 #define V8_AST_VARIABLES_H_
 
 #include "src/ast/ast-value-factory.h"
 #include "src/zone.h"
 
@@ skipping 25 matching lines @@
   // parameter initializers.
   void set_scope(Scope* scope) { scope_ = scope; }
 
   Handle<String> name() const { return name_->string(); }
   const AstRawString* raw_name() const { return name_; }
   VariableMode mode() const { return mode_; }
   bool has_forced_context_allocation() const {
     return force_context_allocation_;
   }
   void ForceContextAllocation() {
+    DCHECK(IsUnallocated() || IsContextSlot());

[Toon Verwaest, 2016/08/19 12:48:52]

This is surprising. I'd hope we wouldn't call ForceContextAllocation on already
allocated variables. I'm fine with cleaning this up in another CL, but I think
that should be an invariant ...

     force_context_allocation_ = true;
   }
   bool is_used() { return is_used_; }
   void set_is_used() { is_used_ = true; }
   MaybeAssignedFlag maybe_assigned() const { return maybe_assigned_; }
   void set_maybe_assigned() { maybe_assigned_ = kMaybeAssigned; }
 
   int initializer_position() { return initializer_position_; }
   void set_initializer_position(int pos) { initializer_position_ = pos; }
 
@@ skipping 33 matching lines @@
     local_if_not_shadowed_ = local;
   }
 
   VariableLocation location() const { return location_; }
   int index() const { return index_; }
   InitializationFlag initialization_flag() const {
     return initialization_flag_;
   }
 
   void AllocateTo(VariableLocation location, int index) {
+    DCHECK(IsUnallocated() || (location_ == location && index_ == index));

[Toon Verwaest, 2016/08/19 12:48:52]

Same here...

     location_ = location;
     index_ = index;
   }
 
   static int CompareIndex(Variable* const* v, Variable* const* w);
 
  private:
   Scope* scope_;
   const AstRawString* name_;
   VariableMode mode_;
@@ skipping 11 matching lines @@
   // Usage info.
   bool force_context_allocation_;  // set by variable resolver
   bool is_used_;
   InitializationFlag initialization_flag_;
   MaybeAssignedFlag maybe_assigned_;
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_AST_VARIABLES_H_