[ast/parsing] Pessimistically assume all top-level variables will be assigned.

src/parsing/parser.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_PARSING_PARSER_H_
 #define V8_PARSING_PARSER_H_
 
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
 #include "src/base/compiler-specific.h"
@@ skipping 805 matching lines @@
 
   // Determine if the expression is a variable proxy and mark it as being used
   // in an assignment or with a increment/decrement operator.
   V8_INLINE static void MarkExpressionAsAssigned(Expression* expression) {
     DCHECK_NOT_NULL(expression);
     if (expression->IsVariableProxy()) {
       expression->AsVariableProxy()->set_is_assigned();
     }
   }
 
+  // We have to pessimistically assume that top-level variables will be
+  // assigned.  This is because they might be accessed by a lazily parsed

[marja, 2017/01/25 12:44:10]

You could fix this comment in this CL :) (There's already discussion about it in
the previous one.)

+  // top-level function, which, for efficiency, we preparse without
+  // variable tracking.  In the case of a script (not a module), they
+  // might also get accessed by another script.
+  V8_INLINE static void MarkTopLevelVariableAsAssigned(Scope* scope,
+                                                       VariableProxy* proxy) {
+    if (scope->is_script_scope() || scope->is_module_scope()) {

[adamk, 2017/01/27 16:07:36]

I thought we currently disable preparsing of functions in modules, and changing
that was blocked on marja's work to preparse inner functions.

Or am I confused and we instead force context allocation for all module-scoped
variables?

+      proxy->set_is_assigned();
+    }
+  }
+
   // Returns true if we have a binary expression between two numeric
   // literals. In that case, *x will be changed to an expression which is the
   // computed value.
   bool ShortcutNumericLiteralBinaryExpression(Expression** x, Expression* y,
                                               Token::Value op, int pos);
 
   // Rewrites the following types of unary expressions:
   // not <literal> -> true / false
   // + <numeric literal> -> <numeric literal>
   // - <numeric literal> -> <numeric literal with value negated>
@@ skipping 340 matching lines @@
 
  private:
   ParserTarget** variable_;
   ParserTarget* previous_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_H_