Rescope arrow-function parameter lists by moving the delta to the parameter scope

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index 2d08a2427e2f02e9ebdb28a3c5a5b9a62cd58803..ec10355d7bd859ba96f04fba6f0888f498c837f9 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -4124,22 +4124,11 @@ void ParserTraits::ParseArrowFunctionFormalParameters(
   }
 
   Expression* initializer = nullptr;
-  if (expr->IsVariableProxy()) {
-    // When the formal parameter was originally seen, it was parsed as a
-    // VariableProxy and recorded as unresolved in the scope.  Here we undo that
-    // parse-time side-effect for parameters that are single-names (not
-    // patterns; for patterns that happens uniformly in
-    // PatternRewriter::VisitVariableProxy).
-    parser_->scope()->RemoveUnresolved(expr->AsVariableProxy());
-  } else if (expr->IsAssignment()) {
+  if (expr->IsAssignment()) {
     Assignment* assignment = expr->AsAssignment();
     DCHECK(!assignment->is_compound());
     initializer = assignment->value();
     expr = assignment->target();
-
-    // TODO(adamk): Only call this if necessary.
-    RewriteParameterInitializerScope(parser_->stack_limit(), initializer,
-                                     parser_->scope(), parameters->scope);
   }
 
   AddFormalParameter(parameters, expr, initializer, end_pos, is_rest);
@@ -4219,16 +4208,17 @@ DoExpression* Parser::ParseDoExpression(bool* ok) {
   return expr;
 }
 
-
 void ParserTraits::ParseArrowFunctionFormalParameterList(
     ParserFormalParameters* parameters, Expression* expr,
-    const Scanner::Location& params_loc,
-    Scanner::Location* duplicate_loc, bool* ok) {
+    const Scanner::Location& params_loc, Scanner::Location* duplicate_loc,
+    Scope::Snapshot& scope_snapshot, bool* ok) {
   if (expr->IsEmptyParentheses()) return;
 
   ParseArrowFunctionFormalParameters(parameters, expr, params_loc.end_pos,
                                      CHECK_OK_VOID);
 
+  scope_snapshot.Reparent(parameters->scope);
+
   if (parameters->Arity() > Code::kMaxArguments) {
     ReportMessageAt(params_loc, MessageTemplate::kMalformedArrowFunParamList);
     *ok = false;