Fix redeclaration of existing var variables in functions with argument context. (#3891)

Fixes #3888

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

tests/jerry/es2015/function-scope2.js

@@ -95,3 +95,17 @@ function i([a], get = () => a, set = (v) => a = v) {
   assert(get() === 3);
 }
 i([1]);
+
+function j(a = eval()) {
+  var a = 3.14;
+
+  try {
+    eval("throw 1; function a() { return 8; }")
+    assert(false)
+  } catch (e) {
+    assert(e === 1)
+  }
+
+  assert(a() === 8)
+}
+j()

tests/jerry/es2015/regresssion-test-issue-3888.js

@@ -0,0 +1,19 @@
+// 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.
+
+function i(id_0, b = (eval("var x"))) {
+    function x() {}
+    eval(!eval("var x = {}; x instanceof assert;"))
+}
+i()