Fix async function call parsing. (#3909)

The "async" identifier processing is delayed until it is detected that it cannot
be part of an arrow expression. The "async" identifier should be processed at this
point, but it was not happened in this case.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/parser/js/js-scanner-ops.c

@@ -242,6 +242,12 @@ scanner_check_arrow_arg (parser_context_t *context_p, /**< context */
   scanner_pop_literal_pool (context_p, scanner_context_p);
 
   parser_stack_pop_uint8 (context_p);
+
+  if (context_p->stack_top_uint8 == SCAN_STACK_USE_ASYNC)
+  {
+    scanner_add_async_literal (context_p, scanner_context_p);
+  }
+
   parser_stack_push_uint8 (context_p, SCAN_STACK_PAREN_EXPRESSION);
 
   if (process_arrow)

tests/jerry/es.next/regresssion-test-issue-3908.js

@@ -0,0 +1,20 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+try {
+  eval("async(a,b+)")
+  assert(false)
+} catch (e) {
+  assert(e instanceof SyntaxError)
+}