Fix parsing unterminated let statement (#4808)

This patch fixes #4754

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik robert.fancsik@h-lab.eu

jerry-core/parser/js/js-parser-statm.c

@@ -1550,6 +1550,10 @@ parser_parse_for_statement_start (parser_context_t *context_p) /**< context */
           break;
         }
 
+        /* FALLTHRU */
+      }
+      case LEXER_KEYW_LET:
+      {
         if (context_p->next_scanner_info_p->source_p == context_p->source_p
             && context_p->next_scanner_info_p->type != SCANNER_TYPE_BLOCK)
         {
@@ -1563,9 +1567,9 @@ parser_parse_for_statement_start (parser_context_t *context_p) /**< context */
         }
 
         context_p->token.type = LEXER_KEYW_LET;
+
         /* FALLTHRU */
       }
-      case LEXER_KEYW_LET:
       case LEXER_KEYW_CONST:
       {
         if (context_p->next_scanner_info_p->source_p == source_p)

tests/jerry/fail/regression-test-issue-4754.js

@@ -0,0 +1,15 @@
+// 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.
+
+class a { b() { for (let