fixes #12 - bug in "bind" decorator on super method call from subclass method

.babelrc

@@ -1,6 +1,6 @@
 {
   "modules": "umd",
-  "loose": "all",
+  "loose": false,
   "compact": true,
   "comments": false,
   "stage": 0

src/decko.js

@@ -33,11 +33,13 @@ let fns = {
 			configurable: true,
 			get() {
 				let value = fn.bind(this);
-				Object.defineProperty(this, key, {
-					value,
-					configurable: true,
-					writable: true
-				});
+				if (target.constructor === this.constructor) {
+					Object.defineProperty(this, key, {
+						value,
+						configurable: true,
+						writable: true
+					});
+				}
 				return value;
 			}
 		};

tests/bind.js

@@ -34,4 +34,38 @@ describe('bind()', () => {
 
 		next();
 	});
+
+	it('should bind when used as a decorator for a class method that invokes a decorated super method', next => {
+		let aValue = 'a',
+			bValue = 'b';
+
+		class A {
+			@bind
+			f() {
+				return {value: aValue, this: this};
+			}
+		}
+
+		class B extends A {
+			@bind
+			f() {
+				let superResult = super.f();
+				return {value: bValue, superValue: superResult.value, this: this};
+			}
+		}
+
+		let b = new B(),
+			result;
+
+
+		// call twice to take into consideration effect of super method call
+		for (let i = 0; i < 2; i++) {
+			result = b.f();
+			expect(result.this).to.equal(b);
+			expect(result.value).to.equal(bValue);
+			expect(result.superValue).to.equal(aValue);
+		}
+
+		next();
+	});
 });