Heuristic for eager parsing works for async functions

src/parsing/parser-base.h

 // Copyright 2012 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.
 
 #ifndef V8_PARSING_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
@@ skipping 1829 matching lines @@
       if (Check(Token::RPAREN)) {
         // ()=>x.  The continuation that looks for the => is in
         // ParseAssignmentExpression.
         classifier()->RecordExpressionError(scanner()->location(),
                                             MessageTemplate::kUnexpectedToken,
                                             Token::String(Token::RPAREN));
         return factory()->NewEmptyParentheses(beg_pos);
       }
       // Heuristically try to detect immediately called functions before
       // seeing the call parentheses.
-      if (peek() == Token::FUNCTION) {
+      if (peek() == Token::FUNCTION ||
+          (peek() == Token::ASYNC && PeekAhead() == Token::FUNCTION)) {
         function_state_->set_next_function_is_likely_called();
       }
       ExpressionT expr = ParseExpressionCoverGrammar(true, CHECK_OK);
       Expect(Token::RPAREN, CHECK_OK);
       return expr;
     }
 
     case Token::CLASS: {
       BindingPatternUnexpectedToken();
       Consume(Token::CLASS);
@@ skipping 3913 matching lines @@
 }
 
 #undef CHECK_OK
 #undef CHECK_OK_CUSTOM
 #undef CHECK_OK_VOID
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H