fix(di): improve error messages for invalid bindings

Fixes angular#1515

Closes angular#1573

Author: pkozlowski-opensource

modules/angular2/src/di/exceptions.js

@@ -163,7 +163,7 @@ export class InvalidBindingError extends Error {
   message:string;
   constructor(binding) {
     super();
-    this.message = `Invalid binding ${binding}`;
+    this.message = `Invalid binding - only instances of Binding and Type are allowed, got: ${binding}`;
   }
 
   toString():string {

modules/angular2/src/di/injector.js

@@ -379,7 +379,7 @@ function _resolveBindings(bindings:List): List {
     } else if (unresolved instanceof List) {
       resolved = _resolveBindings(unresolved);
     } else if (unresolved instanceof BindingBuilder) {
-      throw new InvalidBindingError(unresolved.token);
+      throw new InvalidBindingError('BindingBuilder with ' + unresolved.token + ' token');
     } else {
       throw new InvalidBindingError(unresolved);
     }

modules/angular2/test/di/injector_spec.js

@@ -205,8 +205,11 @@ export function main() {
     });
 
     it('should throw when given invalid bindings', function () {
-      expect(() => Injector.resolveAndCreate(["blah"])).toThrowError('Invalid binding blah');
-      expect(() => Injector.resolveAndCreate([bind("blah")])).toThrowError('Invalid binding blah');
+      expect(() => Injector.resolveAndCreate(["blah"]))
+        .toThrowError('Invalid binding - only instances of Binding and Type are allowed, got: blah');
+      expect(() => Injector.resolveAndCreate([bind("blah")]))
+        .toThrowError('Invalid binding - only instances of Binding and Type are allowed, ' +
+        'got: BindingBuilder with blah token');
     });
 
     it('should provide itself', function () {