fix(router): disallow root segments with matrix params

modules/@angular/router/src/create_url_tree.ts

@@ -19,6 +19,8 @@ export function createUrlTree(
   }
 
   const normalizedCommands = normalizeCommands(commands);
+  validateCommands(normalizedCommands);
+
   if (navigateToRoot(normalizedCommands)) {
     return tree(urlTree.root, new UrlSegment([], {}), urlTree, queryParams, fragment);
   }
@@ -31,6 +33,12 @@ export function createUrlTree(
   return tree(startingPosition.segment, segment, urlTree, queryParams, fragment);
 }
 
+function validateCommands(n: NormalizedNavigationCommands): void {
+  if (n.isAbsolute && n.commands.length > 0 && (typeof n.commands[0] === 'object')) {
+    throw new Error('Root segment cannot have matrix parameters');
+  }
+}
+
 function tree(
     oldSegment: UrlSegment, newSegment: UrlSegment, urlTree: UrlTree, queryParams: Params,
     fragment: string): UrlTree {

modules/@angular/router/test/create_url_tree.spec.ts

@@ -14,13 +14,18 @@ describe('createUrlTree', () => {
     expect(serializer.serialize(t)).toEqual('/');
   });
 
+  it('should error when navigating to the root segment with params', () => {
+    const p = serializer.parse('/');
+    expect(() => createRoot(p, ['/', {p: 11}]))
+        .toThrowError(/Root segment cannot have matrix parameters/);
+  });
+
   it('should support nested segments', () => {
     const p = serializer.parse('/a/b');
     const t = createRoot(p, ['/one', 11, 'two', 22]);
     expect(serializer.serialize(t)).toEqual('/one/11/two/22');
   });
 
-
   it('should stringify positional parameters', () => {
     const p = serializer.parse('/a/b');
     const t = createRoot(p, ['/one', 11]);