fix(compiler): cleanly compile with TypeScript 2.4 (#18456)

Author: chuckjaz

packages/compiler/test/aot/static_symbol_resolver_spec.ts

@@ -459,7 +459,7 @@ export class MockStaticSymbolResolverHost implements StaticSymbolResolverHost {
           const errors =
               diagnostics
                   .map(d => {
-                    const {line, character} = ts.getLineAndCharacterOfPosition(d.file, d.start);
+                    const {line, character} = ts.getLineAndCharacterOfPosition(d.file !, d.start !);
                     return `(${line}:${character}): ${d.messageText}`;
                   })
                   .join('\n');

packages/compiler/test/aot/test_util.ts

@@ -559,8 +559,8 @@ export function expectNoDiagnostics(program: ts.Program) {
 
   function lineInfo(diagnostic: ts.Diagnostic): string {
     if (diagnostic.file) {
-      const start = diagnostic.start;
-      let end = diagnostic.start + diagnostic.length;
+      const start = diagnostic.start !;
+      let end = diagnostic.start ! + diagnostic.length !;
       const source = diagnostic.file.text;
       let lineStart = start;
       let lineEnd = end;