[parser] Reimplement duplicate __proto__ checking

Now that identifiers in the preparser also carry their string, we can simply
check that rather than relying on a weird "keyword". Dropping __proto__ as a
keyword allows us to delist '_' as keyword character.

Change-Id: I775df25f77a84de92a60790ca665f16d52abf4bf
Reviewed-on: https://chromium-review.googlesource.com/c/1329692
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57427}

src/parsing/parser-base.h

@@ -321,7 +321,6 @@ class ParserBase {
   };
 
   class ClassLiteralChecker;
-  class ObjectLiteralChecker;
 
   // ---------------------------------------------------------------------------
   // BlockState and FunctionState implement the parser's scope stack.
@@ -1018,8 +1017,8 @@ class ParserBase {
       bool* is_private);
   ExpressionT ParseMemberInitializer(ClassInfo* class_info, int beg_pos,
                                      bool is_static);
-  ObjectLiteralPropertyT ParseObjectPropertyDefinition(
-      ObjectLiteralChecker* checker, bool* is_computed_name,
+  ObjectLiteralPropertyT ParseObjectPropertyDefinition(bool* has_seen_proto,
+                                                       bool* is_computed_name,
                                                        bool* is_rest_property);
   void ParseArguments(ExpressionListT* args, bool* has_spread,
                       bool maybe_arrow);
@@ -1313,27 +1312,6 @@ class ParserBase {
     return factory()->NewReturnStatement(expr, pos, end_pos);
   }
 
-  // Validation per ES6 object literals.
-  class ObjectLiteralChecker {
-   public:
-    explicit ObjectLiteralChecker(ParserBase* parser)
-        : parser_(parser), has_seen_proto_(false) {}
-
-    void CheckDuplicateProto(Token::Value property);
-
-   private:
-    bool IsProto() const {
-      return this->scanner()->CurrentMatchesContextualEscaped(
-          Token::PROTO_UNDERSCORED);
-    }
-
-    ParserBase* parser() const { return parser_; }
-    Scanner* scanner() const { return parser_->scanner(); }
-
-    ParserBase* parser_;
-    bool has_seen_proto_;
-  };
-
   // Validation per ES6 class literals.
   class ClassLiteralChecker {
    public:
@@ -2354,7 +2332,7 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseMemberInitializer(
 
 template <typename Impl>
 typename ParserBase<Impl>::ObjectLiteralPropertyT
-ParserBase<Impl>::ParseObjectPropertyDefinition(ObjectLiteralChecker* checker,
+ParserBase<Impl>::ParseObjectPropertyDefinition(bool* has_seen_proto,
                                                 bool* is_computed_name,
                                                 bool* is_rest_property) {
   ParseFunctionFlags function_flags = ParseFunctionFlag::kIsNormal;
@@ -2389,8 +2367,14 @@ ParserBase<Impl>::ParseObjectPropertyDefinition(ObjectLiteralChecker* checker,
     case ParsePropertyKind::kValue: {
       DCHECK_EQ(function_flags, ParseFunctionFlag::kIsNormal);
 
-      if (!*is_computed_name) {
-        checker->CheckDuplicateProto(name_token);
+      if (!*is_computed_name &&
+          (name_token == Token::IDENTIFIER || name_token == Token::STRING) &&
+          impl()->IdentifierEquals(name, ast_value_factory()->proto_string())) {
+        if (*has_seen_proto) {
+          classifier()->RecordExpressionError(scanner()->location(),
+                                              MessageTemplate::kDuplicateProto);
+        }
+        *has_seen_proto = true;
       }
       Consume(Token::COLON);
       int beg_pos = peek_position();
@@ -2544,7 +2528,7 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseObjectLiteral() {
 
   bool has_computed_names = false;
   bool has_rest_property = false;
-  ObjectLiteralChecker checker(this);
+  bool has_seen_proto = false;
 
   Consume(Token::LBRACE);
 
@@ -2554,7 +2538,7 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseObjectLiteral() {
     bool is_computed_name = false;
     bool is_rest_property = false;
     ObjectLiteralPropertyT property = ParseObjectPropertyDefinition(
-        &checker, &is_computed_name, &is_rest_property);
+        &has_seen_proto, &is_computed_name, &is_rest_property);
     if (impl()->IsNull(property)) return impl()->FailureExpression();
 
     if (is_computed_name) {
@@ -5860,21 +5844,6 @@ typename ParserBase<Impl>::StatementT ParserBase<Impl>::ParseForAwaitStatement(
   return final_loop;
 }
 
-template <typename Impl>
-void ParserBase<Impl>::ObjectLiteralChecker::CheckDuplicateProto(
-    Token::Value property) {
-  if (property == Token::SMI || property == Token::NUMBER) return;
-
-  if (IsProto()) {
-    if (has_seen_proto_) {
-      this->parser()->classifier()->RecordExpressionError(
-          this->scanner()->location(), MessageTemplate::kDuplicateProto);
-      return;
-    }
-    has_seen_proto_ = true;
-  }
-}
-
 template <typename Impl>
 void ParserBase<Impl>::ClassLiteralChecker::CheckClassMethodName(
     Token::Value property, ParsePropertyKind type, ParseFunctionFlags flags,

src/parsing/parser.h

@@ -329,6 +329,11 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
       const char* name, DeclarationScope* scope,
       ZonePtrList<ClassLiteral::Property>* fields);
 
+  bool IdentifierEquals(const AstRawString* identifier,
+                        const AstRawString* other) {
+    return identifier == other;
+  }
+
   Statement* DeclareClass(const AstRawString* variable_name, Expression* value,
                           ZonePtrList<const AstRawString>* names,
                           int class_token_pos, int end_pos);

src/parsing/preparser.cc

@@ -387,6 +387,12 @@ PreParserStatement PreParser::BuildParameterInitializationBlock(
   return PreParserStatement::Default();
 }
 
+bool PreParser::IdentifierEquals(const PreParserIdentifier& identifier,
+                                 const AstRawString* other) {
+  DCHECK_EQ(identifier.string_ == nullptr, has_error());
+  return identifier.string_ == other;
+}
+
 PreParserExpression PreParser::ExpressionFromIdentifier(
     const PreParserIdentifier& name, int start_position, InferName infer) {
   VariableProxy* proxy = nullptr;

src/parsing/preparser.h

@@ -1146,6 +1146,9 @@ class PreParser : public ParserBase<PreParser> {
                            function_scope);
   }
 
+  bool IdentifierEquals(const PreParserIdentifier& identifier,
+                        const AstRawString* other);
+
   // TODO(nikolaos): The preparser currently does not keep track of labels
   // and targets.
   V8_INLINE PreParserStatement

src/parsing/scanner-inl.h

@@ -234,8 +234,6 @@ static const Token::Value one_char_tokens[] = {
   KEYWORD("with", Token::WITH)                              \
   KEYWORD_GROUP('y')                                        \
   KEYWORD("yield", Token::YIELD)                            \
-  KEYWORD_GROUP('_')                                        \
-  KEYWORD("__proto__", Token::PROTO_UNDERSCORED)            \
   KEYWORD_GROUP('#')                                        \
   KEYWORD("#constructor", Token::PRIVATE_CONSTRUCTOR)
 
@@ -299,12 +297,12 @@ enum class ScanFlags : uint8_t {
 };
 constexpr uint8_t GetScanFlags(char c) {
   return
-      // Keywords are all lowercase and only contain letters and '_'.
+      // Keywords are all lowercase and only contain letters.
       // Note that non-identifier characters do not set this flag, so
       // that it plays well with kTerminatesLiteral
       // TODO(leszeks): We could probably get an even tighter measure
       // here if not all letters are present in keywords.
-      (IsAsciiIdentifier(c) && !IsInRange(c, 'a', 'z') && c != '_'
+      (IsAsciiIdentifier(c) && !IsInRange(c, 'a', 'z')
            ? static_cast<uint8_t>(ScanFlags::kCannotBeKeyword)
            : 0) |
       // Anything that isn't an identifier character will terminate the

src/parsing/token.h

@@ -204,7 +204,6 @@ namespace internal {
   C(AS, "as", 0)                                                   \
   C(FROM, "from", 0)                                               \
   C(NAME, "name", 0)                                               \
-  C(PROTO_UNDERSCORED, "__proto__", 0)                             \
   C(CONSTRUCTOR, "constructor", 0)                                 \
   C(PRIVATE_CONSTRUCTOR, "#constructor", 0)                        \
   C(PROTOTYPE, "prototype", 0)                                     \