build: upgrade to TypeScript 2.7 (#22669)

Fixes: #21571

PR Close #22669

packages/core/src/render3/interfaces/definition.ts

@@ -218,7 +218,7 @@ export interface DirectiveDefArgs<T> {
   /**
    * Factory method used to create an instance of directive.
    */
-  factory: () => T | [T];
+  factory: () => T | ({0: T} & any[]); /* trying to say T | [T, ...any] */
 
   /**
    * Static attributes to set on host element.

packages/core/src/sanitization/html_sanitizer.ts

@@ -256,7 +256,9 @@ export function _sanitizeHtml(defaultDoc: any, unsafeHtmlInput: string): string
 }
 
 function getTemplateContent(el: Node): Node|null {
-  return 'content' in el && isTemplateElement(el) ? el.content : null;
+  return 'content' in (el as any /** Microsoft/TypeScript#21517 */) && isTemplateElement(el) ?
+      el.content :
+      null;
 }
 function isTemplateElement(el: Node): el is HTMLTemplateElement {
   return el.nodeType === Node.ELEMENT_NODE && el.nodeName === 'TEMPLATE';