Implement proper creation of function arguments, let and const declarations. (#3725)

After the rework it is possible to detect use before init errors for function arguments.

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

tests/jerry/es2015/let15.js

@@ -0,0 +1,65 @@
+// 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 {
+    f()
+    assert(false)
+  } catch (e) {
+    assert(e instanceof ReferenceError)
+  }
+
+  let a = 1;
+
+  try {
+    f()
+    assert(false)
+  } catch (e) {
+    assert(e instanceof ReferenceError)
+  }
+
+  let [b] = [2];
+
+  try {
+    f()
+    assert(false)
+  } catch (e) {
+    assert(e instanceof ReferenceError)
+  }
+
+  const {c} = { c:3 };
+
+  f();
+  function f() { assert(a + b + c === 6) }
+}
+
+{
+  let a = 3;
+  let [b] = [4];
+  const {c} = { c:5 };
+
+  let f = (function () { assert(a + b + c === 12) })
+  f();
+
+  {
+    function g() { assert(a + b + c === 12) }
+    g();
+  }
+}
+
+{
+  class C {}
+
+  assert(function () { return C } () === C);
+}