[ast] Mark temporaries as maybe-assigned by default.

src/ast/scopes.h

 // Copyright 2012 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_SCOPES_H_
 #define V8_AST_SCOPES_H_
 
 #include "src/base/compiler-specific.h"
 #include "src/base/hashmap.h"
 #include "src/globals.h"
@@ skipping 192 matching lines @@
   // addition introduced a new unresolved variable which may end up being
   // allocated globally as a "ghost" variable. RemoveUnresolved removes
   // such a variable again if it was added; otherwise this is a no-op.
   bool RemoveUnresolved(VariableProxy* var);
 
   // Creates a new temporary variable in this scope's TemporaryScope.  The
   // name is only used for printing and cannot be used to find the variable.
   // In particular, the only way to get hold of the temporary is by keeping the
   // Variable* around.  The name should not clash with a legitimate variable
   // names.
+  // Only pass kNotAssigned if you know what you are doing.

[adamk, 2017/02/15 19:03:59]

Not sure this comment is helpful. If this is dangerous enough, should the
version that takes a maybe_assigned argument be private?

   // TODO(verwaest): Move to DeclarationScope?
-  Variable* NewTemporary(const AstRawString* name);
+  Variable* NewTemporary(const AstRawString* name,
+                         MaybeAssignedFlag maybe_assigned = kMaybeAssigned);
 
   // ---------------------------------------------------------------------------
   // Illegal redeclaration support.
 
   // Check if the scope has conflicting var
   // declarations, i.e. a var declaration that has been hoisted from a nested
   // scope over a let binding of the same name.
   Declaration* CheckConflictingVarDeclarations();
 
   // Check if the scope has a conflicting lexical declaration that has a name in
@@ skipping 736 matching lines @@
   void AllocateModuleVariables();
 
  private:
   ModuleDescriptor* module_descriptor_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_AST_SCOPES_H_