[parser] Reduce reliance on has_error()

Instead we can typically check whether the expression or statement we just
parsed indicate failure.

Bug: v8:8363, v8:7926
Change-Id: I477511f9f2f0e615a07285db858a237af8478edc
Reviewed-on: https://chromium-review.googlesource.com/c/1323553Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57322}

src/parsing/parser-base.h

@@ -1936,7 +1936,7 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseArrayLiteral() {
     values.Add(elem);
     if (peek() != Token::RBRACK) {
       Expect(Token::COMMA);
-      if (has_error()) return impl()->FailureExpression();
+      if (elem->IsFailureExpression()) return elem;
     }
   }
 
@@ -2527,7 +2527,7 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseObjectLiteral() {
     bool is_rest_property = false;
     ObjectLiteralPropertyT property = ParseObjectPropertyDefinition(
         &checker, &is_computed_name, &is_rest_property);
-    if (has_error()) return impl()->FailureExpression();
+    if (impl()->IsNull(property)) return impl()->FailureExpression();
 
     if (is_computed_name) {
       has_computed_names = true;
@@ -4127,7 +4127,6 @@ ParserBase<Impl>::ParseArrowFunctionLiteral(
         // Validate parameter names. We can do this only after preparsing the
         // function, since the function can declare itself strict.
         ValidateFormalParameters(language_mode(), false);
-        if (has_error()) return impl()->FailureExpression();
 
         DCHECK_NULL(produced_preparsed_scope_data);
 
@@ -4541,11 +4540,11 @@ ParserBase<Impl>::ParseStatementList(StatementListT* body,
     }
 
     StatementT stat = ParseStatementListItem();
+    if (impl()->IsNull(stat)) return kLazyParsingComplete;
+
     body->Add(stat);
     may_abort = false;
 
-    if (has_error()) return kLazyParsingComplete;
-
     if (!impl()->IsStringLiteral(stat)) break;
 
     if (use_strict) {
@@ -4591,7 +4590,7 @@ ParserBase<Impl>::ParseStatementList(StatementListT* body,
 
   while (peek() != end_token) {
     StatementT stat = ParseStatementListItem();
-    if (has_error()) return kLazyParsingComplete;
+    if (impl()->IsNull(stat)) return kLazyParsingComplete;
     if (stat->IsEmptyStatement()) continue;
     body->Add(stat);
   }
@@ -4772,7 +4771,7 @@ typename ParserBase<Impl>::BlockT ParserBase<Impl>::ParseBlock(
 
     while (peek() != Token::RBRACE) {
       StatementT stat = ParseStatementListItem();
-      RETURN_IF_PARSE_ERROR;
+      if (impl()->IsNull(stat)) return body;
       if (stat->IsEmptyStatement()) continue;
       statements.Add(stat);
     }
@@ -4917,6 +4916,7 @@ ParserBase<Impl>::ParseExpressionOrLabelledStatement(
 
   // Parsed expression statement, followed by semicolon.
   ExpectSemicolon();
+  if (expr->IsFailureExpression()) return impl()->NullStatement();
   return factory()->NewExpressionStatement(expr, pos);
 }
 
@@ -5228,7 +5228,7 @@ typename ParserBase<Impl>::StatementT ParserBase<Impl>::ParseSwitchStatement(
         while (peek() != Token::CASE && peek() != Token::DEFAULT &&
                peek() != Token::RBRACE) {
           StatementT stat = ParseStatementListItem();
-          RETURN_IF_PARSE_ERROR;
+          if (impl()->IsNull(stat)) return stat;
           if (stat->IsEmptyStatement()) continue;
           statements.Add(stat);
         }

src/parsing/parser.cc

@@ -899,7 +899,7 @@ void Parser::ParseModuleItemList(ScopedPtrList<Statement>* body) {
   DCHECK(scope()->is_module_scope());
   while (peek() != Token::EOS) {
     Statement* stat = ParseModuleItem();
-    if (has_error()) return;
+    if (stat == nullptr) return;
     if (stat->IsEmptyStatement()) continue;
     body->Add(stat);
   }
@@ -955,8 +955,10 @@ ZoneChunkList<Parser::ExportClauseData>* Parser::ParseExportClause(
     }
     export_data->push_back({export_name, local_name, location});
     if (peek() == Token::RBRACE) break;
-    Expect(Token::COMMA);
-    if (has_error()) break;
+    if (V8_UNLIKELY(!Check(Token::COMMA))) {
+      ReportUnexpectedToken(Next());
+      break;
+    }
   }
 
   Expect(Token::RBRACE);
@@ -1176,13 +1178,13 @@ Statement* Parser::ParseExportDefault() {
     }
   }
 
-  if (has_error()) return nullptr;
-  DCHECK_EQ(local_names.length(), 1);
-  module()->AddExport(local_names.first(),
-                      ast_value_factory()->default_string(), default_loc,
-                      zone());
+  if (result != nullptr) {
+    DCHECK_EQ(local_names.length(), 1);
+    module()->AddExport(local_names.first(),
+                        ast_value_factory()->default_string(), default_loc,
+                        zone());
+  }
 
-  DCHECK_NOT_NULL(result);
   return result;
 }
 
@@ -1686,7 +1688,7 @@ void Parser::ParseAndRewriteGeneratorFunctionBody(
   Expression* initial_yield = BuildInitialYield(pos, kind);
   body->Add(
       factory()->NewExpressionStatement(initial_yield, kNoSourcePosition));
-  ParseStatementList(body, Token::RBRACE, !has_error());
+  ParseStatementList(body, Token::RBRACE);
 }
 
 void Parser::ParseAndRewriteAsyncGeneratorFunctionBody(
@@ -1719,7 +1721,7 @@ void Parser::ParseAndRewriteAsyncGeneratorFunctionBody(
     Expression* initial_yield = BuildInitialYield(pos, kind);
     statements.Add(
         factory()->NewExpressionStatement(initial_yield, kNoSourcePosition));
-    ParseStatementList(&statements, Token::RBRACE, !has_error());
+    ParseStatementList(&statements, Token::RBRACE);
 
     // Don't create iterator result for async generators, as the resume methods
     // will create it.
@@ -2587,9 +2589,9 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
   scope->SetScopeName(function_name);
 #endif
 
-  if (!is_wrapped) {
-    Expect(Token::LPAREN);
-    if (has_error()) return nullptr;
+  if (!is_wrapped && V8_UNLIKELY(!Check(Token::LPAREN))) {
+    ReportUnexpectedToken(Next());
+    return nullptr;
   }
   scope->set_start_position(position());
 

src/parsing/preparser.h

@@ -210,6 +210,9 @@ class PreParserExpression {
   }
 
   bool IsNull() const { return TypeField::decode(code_) == kNull; }
+  bool IsFailureExpression() const {
+    return TypeField::decode(code_) == kFailure;
+  }
 
   bool IsIdentifier() const {
     return TypeField::decode(code_) == kIdentifierExpression;