[parser] binding arguments var declaration in inner_scope

when has_simple_parameters_ is false in DeclareArguments

- According to https://tc39.es/ecma262/multipage/ordinary-and-exotic-objects-behaviours.html#sec-functiondeclarationinstantiation
step 28, arguments var declaration in function should be binding to
arguments parameterBindings when has_simple_parameters_ is false.
- According to https://tc39.es/ecma262/multipage/ordinary-and-exotic-objects-behaviours.html#sec-funct>
step 18, we should set arguments_ is nullptr if "arguments" is an element of lexicalNames
only when has_simple_parameters is true.

Bug: v8:12671
Change-Id: I542f80e2c8653ae05b65feb0036e4ade2e653a53
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3499251
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79382}

src/ast/scopes.cc

@@ -747,14 +747,28 @@ void DeclarationScope::DeclareArguments(AstValueFactory* ast_value_factory) {
   DCHECK(is_function_scope());
   DCHECK(!is_arrow_scope());
 
+  // Because when arguments_ is not nullptr, we already declared
+  // "arguments exotic object" to add it into parameters before
+  // impl()->InsertShadowingVarBindingInitializers, so here
+  // only declare "arguments exotic object" when arguments_
+  // is nullptr
+  if (arguments_ != nullptr) {
+    return;
+  }
+
   // Declare 'arguments' variable which exists in all non arrow functions.  Note
   // that it might never be accessed, in which case it won't be allocated during
   // variable allocation.
-  bool was_added;
+  bool was_added = false;
+
   arguments_ =
       Declare(zone(), ast_value_factory->arguments_string(), VariableMode::kVar,
               NORMAL_VARIABLE, kCreatedInitialized, kNotAssigned, &was_added);
-  if (!was_added && IsLexicalVariableMode(arguments_->mode())) {
+  // According to ES#sec-functiondeclarationinstantiation step 18
+  // we should set argumentsObjectNeeded to false if has lexical
+  // declared arguments only when hasParameterExpressions is false
+  if (!was_added && IsLexicalVariableMode(arguments_->mode()) &&
+      has_simple_parameters_) {
     // Check if there's lexically declared variable named arguments to avoid
     // redeclaration. See ES#sec-functiondeclarationinstantiation, step 20.
     arguments_ = nullptr;

src/parsing/parser-base.h

@@ -4405,6 +4405,16 @@ void ParserBase<Impl>::ParseFunctionBody(
           impl()->ReportVarRedeclarationIn(conflict, inner_scope);
         }
       }
+
+      // According to ES#sec-functiondeclarationinstantiation step 27,28
+      // when hasParameterExpressions is true, we need bind var declared
+      // arguments to "arguments exotic object", so we here first declare
+      // "arguments exotic object", then var declared arguments will be
+      // initialized with "arguments exotic object"
+      if (!IsArrowFunction(kind)) {
+        function_scope->DeclareArguments(ast_value_factory());
+      }
+
       impl()->InsertShadowingVarBindingInitializers(inner_block);
     }
   }
@@ -4413,9 +4423,6 @@ void ParserBase<Impl>::ParseFunctionBody(
                            allow_duplicate_parameters);
 
   if (!IsArrowFunction(kind)) {
-    // Declare arguments after parsing the function since lexical 'arguments'
-    // masks the arguments object. Declare arguments before declaring the
-    // function var since the arguments object masks 'function arguments'.
     function_scope->DeclareArguments(ast_value_factory());
   }
 

test/mjsunit/regress/regress-v8-12671.js

@@ -0,0 +1,74 @@
+// Copyright 2022 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.
+
+// spec:
+// https://tc39.es/ecma262/multipage/ordinary-and-exotic-objects-behaviours.html
+// #sec-functiondeclarationinstantiation
+
+// This regession focus on checking [var declared "arguments" should bind to
+// "arguments exotic object" when has_simple_parameters_ is false and
+// inner_scope has var declared "arguments"]
+
+
+// according to ES#sec-functiondeclarationinstantiation step 8,
+// hasParameterExpressions is false, and according to step 15-18,
+// argumentsObjectNeeded is true, according to step 27,
+// var declared arguments should bind to arguments exotic object
+function no_parameters_and_non_lexical_arguments() {
+  assertEquals(typeof arguments, 'object');
+  var arguments;
+}
+no_parameters_and_non_lexical_arguments()
+
+// according to ES#sec-functiondeclarationinstantiation step 8,
+// hasParameterExpressions is false, and according to step 15-18,
+// argumentsObjectNeeded is true, according to step 28,
+// var declared arguments should bind to arguments exotic object
+function destructuring_parameters_and_non_lexical_arguments([_]) {
+  assertEquals(typeof arguments, 'object');
+  var arguments;
+}
+destructuring_parameters_and_non_lexical_arguments([])
+
+// according to ES#sec-functiondeclarationinstantiation step 8,
+// hasParameterExpressions is false, and according to step 15-18,
+// argumentsObjectNeeded is true, according to step 28,
+// var declared arguments should bind to arguments exotic object
+function rest_parameters_and_non_lexical_arguments(..._) {
+  assertEquals(typeof arguments, 'object');
+  var arguments;
+}
+rest_parameters_and_non_lexical_arguments()
+
+// according to ES#sec-functiondeclarationinstantiation step 8,
+// hasParameterExpressions is true, and according to step 15-18,
+// argumentsObjectNeeded is true, according to step 28,
+// var declared arguments should bind to arguments exotic object
+function initializer_parameters_and_non_lexical_arguments(_ = 0) {
+  assertEquals(typeof arguments, 'object');
+  var arguments;
+}
+initializer_parameters_and_non_lexical_arguments()
+
+// according to ES#sec-functiondeclarationinstantiation step 8,
+// hasParameterExpressions is true, and according to step 15-18,
+// and argumentsObjectNeeded is true, according to step 34, should
+// throw because access to let declared arguments
+function initializer_parameters_and_lexical_arguments(_ = 0) {
+  return typeof arguments;
+  let arguments;
+}
+
+assertThrows(initializer_parameters_and_lexical_arguments);
+
+// according to ES#sec-functiondeclarationinstantiation step 8,
+// hasParameterExpressions is false, and according to step 15-18,
+// argumentsObjectNeeded is false, according to step 34,
+// should throw because access to let declared arguments
+function simple_parameters_and_lexical_arguments(_) {
+  return typeof arguments;
+  let arguments;
+}
+
+assertThrows(simple_parameters_and_lexical_arguments);