refactor(reflection): improved error message

modules/angular2/src/reflection/reflection_capabilities.dart

@@ -1,6 +1,7 @@
 library reflection.reflection_capabilities;
 
 import 'reflection.dart';
+import 'package:angular2/src/facade/lang.dart';
 import 'types.dart';
 import 'dart:mirrors';
 
@@ -45,7 +46,7 @@ class ReflectionCapabilities {
             create(name, [a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]).reflectee;
     }
 
-    throw "Factory cannot take more than 10 arguments";
+    throw "Cannot create a factory for '${stringify(type)}' because its constructor has more than 10 arguments";
   }
 
   List<List> parameters(typeOrFunc) {

modules/angular2/src/reflection/reflection_capabilities.ts

@@ -1,4 +1,4 @@
-import {Type, isPresent, global} from 'angular2/src/facade/lang';
+import {Type, isPresent, global, stringify} from 'angular2/src/facade/lang';
 import {List, ListWrapper} from 'angular2/src/facade/collection';
 import {GetterFn, SetterFn, MethodFn} from './types';
 
@@ -39,7 +39,8 @@ export class ReflectionCapabilities {
         };
     };
 
-    throw new Error("Factory cannot take more than 10 arguments");
+    throw new Error(
+        `Cannot create a factory for '${stringify(t)}' because its constructor has more than 10 arguments`);
   }
 
   _zipTypesAndAnnotaions(paramTypes, paramAnnotations): List<List<any>> {

modules/angular2/test/core/compiler/reflection_capabilities_spec.js

@@ -31,6 +31,18 @@ export function main() {
   }
 
   describe('reflection capabilities', () => {
+    describe("factory", () => {
+      it("should create a factory for a type", () => {
+        var f = rc.factory(ClassWithField);
+        expect(f("value").field).toEqual("value");
+      });
+
+      it("should throw when a constructor has more than 10 args", () => {
+        expect(() => rc.factory(ClassWith11Fields)).toThrowError(
+            new RegExp(`has more than 10 arguments`));
+      });
+    });
+
     it('can read out class annotations through annotations key', () => {
       assertTestClassAnnotations(rc.annotations(TestClass));
     });
@@ -115,6 +127,17 @@ class TestClassTypesOnly {
   constructor(a: P1, b: P2) {}
 }
 
+class ClassWithField {
+  field;
+  constructor(field) {
+    this.field = field;
+  }
+}
+class ClassWith11Fields {
+  constructor(a0,a1,a2,a3,a4,a5,a6,a7,a8,a9,a10) {
+  }
+}
+
 // Mocking the data stored in global.Reflect as if TS was compiling TestClass above.
 var mockDataForTestClassTypesOnly = {
   'annotations': null,