fix(router): throw when generating non-terminal link

Closes #3979

Closes #4092

modules/angular2/src/router/route_registry.ts

@@ -200,6 +200,7 @@ export class RouteRegistry {
   generate(linkParams: any[], parentComponent: any): Instruction {
     let segments = [];
     let componentCursor = parentComponent;
+    var lastInstructionIsTerminal = false;
 
     for (let i = 0; i < linkParams.length; i += 1) {
       let segment = linkParams[i];
@@ -233,9 +234,26 @@ export class RouteRegistry {
       }
       segments.push(response);
       componentCursor = response.componentType;
+      lastInstructionIsTerminal = response.terminal;
     }
 
-    var instruction: Instruction = this._generateRedirects(componentCursor);
+    var instruction: Instruction = null;
+
+    if (!lastInstructionIsTerminal) {
+      instruction = this._generateRedirects(componentCursor);
+
+      if (isPresent(instruction)) {
+        let lastInstruction = instruction;
+        while (isPresent(lastInstruction.child)) {
+          lastInstruction = lastInstruction.child;
+        }
+        lastInstructionIsTerminal = lastInstruction.component.terminal;
+      }
+      if (!lastInstructionIsTerminal) {
+        throw new BaseException(
+            `Link "${ListWrapper.toJSON(linkParams)}" does not resolve to a terminal instruction.`);
+      }
+    }
 
 
     while (segments.length > 0) {

modules/angular2/test/router/route_registry_spec.ts

@@ -79,9 +79,8 @@ export function main() {
       expect(url).toEqual('first/one/second/two');
     });
 
-    it('should geneate params as an empty StringMap when no params are given', () => {
-      registry.config(RootHostCmp,
-                      new Route({path: '/test/...', component: DummyParentParamCmp, as: 'test'}));
+    it('should generate params as an empty StringMap when no params are given', () => {
+      registry.config(RootHostCmp, new Route({path: '/test', component: DummyCmpA, as: 'test'}));
       var instruction = registry.generate(['test'], RootHostCmp);
       expect(instruction.component.params).toEqual({});
     });
@@ -232,6 +231,13 @@ export function main() {
       }
     });
 
+    it('should throw when linkParams are not terminal', () => {
+      registry.config(RootHostCmp,
+                      new Route({path: '/first/...', component: DummyParentCmp, as: 'first'}));
+      expect(() => { registry.generate(['first'], RootHostCmp); })
+          .toThrowError('Link "["first"]" does not resolve to a terminal instruction.');
+    });
+
     it('should match matrix params on child components and query params on the root component',
        inject([AsyncTestCompleter], (async) => {
          registry.config(RootHostCmp, new Route({path: '/first/...', component: DummyParentCmp}));