Add testcase that unhandled exception occurs when a private variable increments. (#5238)

Author: hvwyl

tests/jerry/private_fields.js

@@ -53,6 +53,7 @@ check_syntax_error("class A { static *#bar(x) { } #bar }");
 check_syntax_error("class A { async *#bar(x) { } #bar }");
 check_syntax_error("class A { async #bar(x) { } #bar }");
 check_syntax_error("class A { *#bar(x) { } #bar }");
+check_syntax_error("class A { #a; foo(){ ++this.#a; --this.#a; this.#a++; this.#a--; }}");
 
 
 class A {
@@ -350,3 +351,23 @@ class Q extends Array {
 
 var var18 = new Q();
 assert(var18.b() == 1);
+
+class R {
+  #a = 0;
+  test() {
+    ++this.#a;
+    assert(this.#a == 1);
+    assert(++this.#a == 2);
+    --this.#a;
+    assert(this.#a == 1);
+    assert(--this.#a == 0);
+    this.#a++;
+    assert(this.#a == 1);
+    assert(this.#a++ == 1);
+    this.#a--;
+    assert(this.#a == 1);
+    assert(this.#a-- == 1);
+  }
+}
+var var19 = new R();
+var19.test();

tests/jerry/regression-test-issue-5238.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.
+
+class A {
+    #a = 0;
+    incr() {
+        this.#a++;
+    }
+}