Pull in my rewritten Function.prototype.bind polyfill from upstream

src/test/all.js

@@ -12,40 +12,24 @@ if (!Fp.bind) {
   Fp.bind = function(context) {
     var func = this;
     var args = slice.call(arguments, 1);
-    var bound;
 
-    if (func.prototype) {
-      if (args.length > 0) {
-        bound = function() {
-          return func.apply(
-            !(this instanceof func) && context || this,
-            args.concat(slice.call(arguments))
-          );
-        };
-      } else {
-        bound = function() {
-          return func.apply(
-            !(this instanceof func) && context || this,
-            arguments
-          );
-        };
-      }
-
-      bound.prototype = Object.create(func.prototype);
-
-    } else if (args.length > 0) {
-      bound = function() {
-        return func.apply(
-          context || this,
-          args.concat(slice.call(arguments))
-        );
-      };
-    } else {
-      bound = function() {
-        return func.apply(context || this, arguments);
-      };
+    function bound() {
+      var invokedAsConstructor = func.prototype && (this instanceof func);
+      return func.apply(
+        // Ignore the context parameter when invoking the bound function
+        // as a constructor. Note that this includes not only constructor
+        // invocations using the new keyword but also calls to base class
+        // constructors such as BaseClass.call(this, ...) or super(...).
+        !invokedAsConstructor && context || this,
+        args.concat(slice.call(arguments))
+      );
     }
 
+    // The bound function must share the .prototype of the unbound
+    // function so that any object created by one constructor will count
+    // as an instance of both constructors.
+    bound.prototype = func.prototype;
+
     return bound;
   };
 }