Add support for function argument initializers. (#2571)

EcmaScript 2015 14.1.

Note: arrow functions with default arguments are not supported yet.

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

tests/jerry/es2015/function-param-init.js

@@ -0,0 +1,81 @@
+// 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.
+
+var local = 0;
+
+switch(0) { /* This switch forces a pre-scanner run. */
+default:
+
+  function f(a = (5, local = 6),
+             b = ((5 + function(a = 6) { return a }() * 3)),
+             c,
+             d = true ? 1 : 2)
+  {
+    return "" + a + ", " + b + ", " + c + ", " + d;
+  }
+
+  assert(f() === "6, 23, undefined, 1");
+  assert(local === 6);
+
+  var obj = {
+    f: function(a = [10,,20],
+                b,
+                c = Math.cos(0),
+                d)
+    {
+      return "" + a + ", " + b + ", " + c + ", " + d;
+    }
+  };
+
+  assert(obj.f() === "10,,20, undefined, 1, undefined");
+
+  function g(a, b = (local = 7)) { }
+
+  local = 0;
+  g();
+  assert(local === 7);
+
+  local = 0;
+  g(0);
+  assert(local === 7);
+
+  local = 0;
+  g(0, undefined);
+  assert(local === 7);
+
+  local = 0;
+  g(0, null);
+  assert(local === 0);
+
+  local = 0;
+  g(0, false);
+  assert(local === 0);
+  break;
+}
+
+function CheckSyntaxError(str)
+{
+  try {
+    eval(str);
+    assert(false);
+  } catch (e) {
+    assert(e instanceof SyntaxError);
+  }
+}
+
+CheckSyntaxError('function x(a += 5) {}');
+CheckSyntaxError('function x(a =, b) {}');
+CheckSyntaxError('function x(a = (b) {}');
+CheckSyntaxError('function x(a, a = 5) {}');
+CheckSyntaxError('function x(a = 5, a) {}');