Fix "this" value in lazily-parsed module functions.

When preparsing top-level functions in a module, we didn't track unresolved variables. Consequently, "this" ended up referencing the global "this", which has the wrong value (in a module "this" is supposed to be the undefined value). This patch fixes that. This also lets us stop forcing context allocation of all variables in module scopes, which the patch takes care of as well. Bug: chromium:791334 Change-Id: Ifac1f1adc033f3facfb3d29dd4bca32ee27bffcf Reviewed-on: https://chromium-review.googlesource.com/808938 Reviewed-by: Marja Hölttä <marja@chromium.org> Reviewed-by: Adam Klein <adamk@chromium.org> Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org> Commit-Queue: Georg Neis <neis@chromium.org> Cr-Commit-Position: refs/heads/master@{#50025}

Author: GeorgNeis

src/ast/scopes.cc

@@ -147,8 +147,6 @@ Scope::Scope(Zone* zone, Scope* outer_scope, ScopeType scope_type)
  DCHECK_NE(SCRIPT_SCOPE, scope_type);
  SetDefaults();
  set_language_mode(outer_scope->language_mode());
- force_context_allocation_ =
- !is_function_scope() && outer_scope->has_forced_context_allocation();
  outer_scope_->AddInnerScope(this);
 }
 
@@ -1370,12 +1368,8 @@ bool Scope::AllowsLazyParsingWithoutUnresolvedVariables(
  if (s->is_catch_scope()) continue;
  // With scopes do not introduce variables that need allocation.
  if (s->is_with_scope()) continue;
- // Module scopes context-allocate all variables, and have no
- // {this} or {arguments} variables whose existence depends on
- // references to them.
- if (s->is_module_scope()) continue;
- // Only block scopes and function scopes should disallow preparsing.
- DCHECK(s->is_block_scope() || s->is_function_scope());
+ DCHECK(s->is_module_scope() || s->is_block_scope() ||
+ s->is_function_scope());
  return false;
  }
  return true;
@@ -1734,9 +1728,6 @@ void Scope::Print(int n) {
  if (scope->was_lazily_parsed()) Indent(n1, "// lazily parsed\n");
  if (scope->ShouldEagerCompile()) Indent(n1, "// will be compiled\n");
  }
- if (has_forced_context_allocation()) {
- Indent(n1, "// forces context allocation\n");
- }
  if (num_stack_slots_ > 0) {
  Indent(n1, "// ");
  PrintF("%d stack slots\n", num_stack_slots_);
@@ -2111,11 +2102,8 @@ bool Scope::MustAllocateInContext(Variable* var) {
  // an eval() call or a runtime with lookup), it must be allocated in the
  // context.
  //
- // Exceptions: If the scope as a whole has forced context allocation, all
- // variables will have context allocation, even temporaries. Otherwise
- // temporary variables are always stack-allocated. Catch-bound variables are
+ // Temporary variables are always stack-allocated. Catch-bound variables are
  // always context-allocated.
- if (has_forced_context_allocation()) return true;
  if (var->mode() == TEMPORARY) return false;
  if (is_catch_scope()) return true;
  if ((is_script_scope() || is_eval_scope()) &&

src/ast/scopes.h

@@ -334,14 +334,6 @@ class V8_EXPORT_PRIVATE Scope : public NON_EXPORTED_BASE(ZoneObject) {
  bool is_hidden() const { return is_hidden_; }
  void set_is_hidden() { is_hidden_ = true; }
 
- // In some cases we want to force context allocation for a whole scope.
- void ForceContextAllocation() {
- DCHECK(!already_resolved_);
- force_context_allocation_ = true;
- }
- bool has_forced_context_allocation() const {
- return force_context_allocation_;
- }
  void ForceContextAllocationForParameters() {
  DCHECK(!already_resolved_);
  force_context_allocation_for_parameters_ = true;

src/parsing/parser.cc

@@ -690,7 +690,6 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info) {
  var->AllocateTo(VariableLocation::PARAMETER, 0);
 
  PrepareGeneratorVariables();
- scope->ForceContextAllocation();
  Expression* initial_yield =
  BuildInitialYield(kNoSourcePosition, kGeneratorFunction);
  body->Add(