refactor: utilize type narrowing

aio/content/examples/testing/src/app/hero/hero-detail.service.ts

@@ -15,7 +15,7 @@ export class HeroDetailService {
   // Returns a clone which caller may modify safely
   getHero(id: number | string): Observable<Hero> {
     if (typeof id === 'string') {
-      id = parseInt(id as string, 10);
+      id = parseInt(id, 10);
     }
     return this.heroService.getHero(id).pipe(
       map(hero => {

aio/content/examples/testing/src/app/model/hero.service.ts

@@ -18,7 +18,7 @@ export class HeroService {
   constructor(private http: HttpClient) { }
 
   /** GET heroes from the server */
-  getHeroes (): Observable<Hero[]> {
+  getHeroes(): Observable<Hero[]> {
     return this.http.get<Hero[]>(this.heroesUrl)
       .pipe(
         tap(heroes => this.log(`fetched heroes`)),
@@ -29,7 +29,7 @@ export class HeroService {
   /** GET hero by id. Return `undefined` when id not found */
   getHero<Data>(id: number | string): Observable<Hero> {
     if (typeof id === 'string') {
-      id = parseInt(id as string, 10);
+      id = parseInt(id, 10);
     }
     const url = `${this.heroesUrl}/?id=${id}`;
     return this.http.get<Hero[]>(url)
@@ -46,14 +46,14 @@ export class HeroService {
   //////// Save methods //////////
 
   /** POST: add a new hero to the server */
-  addHero (hero: Hero): Observable<Hero> {
+  addHero(hero: Hero): Observable<Hero> {
     return this.http.post<Hero>(this.heroesUrl, hero, httpOptions).pipe(
-      tap((hero: Hero) => this.log(`added hero w/ id=${hero.id}`)),
+      tap((addedHero) => this.log(`added hero w/ id=${addedHero.id}`)),
       catchError(this.handleError<Hero>('addHero'))
     );
   }
   /** DELETE: delete the hero from the server */
-  deleteHero (hero: Hero | number): Observable<Hero> {
+  deleteHero(hero: Hero | number): Observable<Hero> {
     const id = typeof hero === 'number' ? hero : hero.id;
     const url = `${this.heroesUrl}/${id}`;
 
@@ -64,7 +64,7 @@ export class HeroService {
   }
 
   /** PUT: update the hero on the server */
-  updateHero (hero: Hero): Observable<any> {
+  updateHero(hero: Hero): Observable<any> {
     return this.http.put(this.heroesUrl, hero, httpOptions).pipe(
       tap(_ => this.log(`updated hero id=${hero.id}`)),
       catchError(this.handleError<any>('updateHero'))
@@ -75,7 +75,7 @@ export class HeroService {
    * This error handler lets the app continue to run as if no error occurred.
    * @param operation - name of the operation that failed
    */
-  private handleError<T> (operation = 'operation') {
+  private handleError<T>(operation = 'operation') {
     return (error: HttpErrorResponse): Observable<T> => {
 
       // TODO: send the error to remote logging infrastructure

aio/content/examples/testing/src/app/model/testing/test-hero.service.ts

@@ -42,9 +42,9 @@ export class TestHeroService extends HeroService {
 
   getHero(id: number | string): Observable<Hero> {
     if (typeof id === 'string') {
-      id = parseInt(id as string, 10);
+      id = parseInt(id, 10);
     }
-    let hero = this.heroes.find(h => h.id === id);
+    const hero = this.heroes.find(h => h.id === id);
     return this.lastResult = asyncData(hero);
   }
 

packages/animations/browser/src/dsl/animation_ast_builder.ts

@@ -244,12 +244,12 @@ export class AnimationAstBuilderVisitor implements AnimationDslVisitor {
       (metadata.styles as(ɵStyleData | string)[]).forEach(styleTuple => {
         if (typeof styleTuple == 'string') {
           if (styleTuple == AUTO_STYLE) {
-            styles.push(styleTuple as string);
+            styles.push(styleTuple);
           } else {
             context.errors.push(`The provided style string value ${styleTuple} is not allowed.`);
           }
         } else {
-          styles.push(styleTuple as ɵStyleData);
+          styles.push(styleTuple);
         }
       });
     } else {
@@ -518,7 +518,7 @@ function consumeOffset(styles: ɵStyleData | string | (ɵStyleData | string)[]):
       }
     });
   } else if (isObject(styles) && styles.hasOwnProperty('offset')) {
-    const obj = styles as ɵStyleData;
+    const obj = styles;
     offset = parseFloat(obj['offset'] as string);
     delete obj['offset'];
   }
@@ -534,8 +534,8 @@ function constructTimingAst(value: string | number | AnimateTimings, errors: any
   if (value.hasOwnProperty('duration')) {
     timings = value as AnimateTimings;
   } else if (typeof value == 'number') {
-    const duration = resolveTiming(value as number, errors).duration;
-    return makeTimingAst(duration as number, 0, '');
+    const duration = resolveTiming(value, errors).duration;
+    return makeTimingAst(duration, 0, '');
   }
 
   const strValue = value as string;

packages/animations/browser/src/dsl/animation_transition_expr.ts

@@ -13,9 +13,8 @@ export function parseTransitionExpr(
     transitionValue: string | TransitionMatcherFn, errors: string[]): TransitionMatcherFn[] {
   const expressions: TransitionMatcherFn[] = [];
   if (typeof transitionValue == 'string') {
-    (<string>transitionValue)
-        .split(/\s*,\s*/)
-        .forEach(str => parseInnerTransitionStr(str, expressions, errors));
+    transitionValue.split(/\s*,\s*/).forEach(
+        str => parseInnerTransitionStr(str, expressions, errors));
   } else {
     expressions.push(<TransitionMatcherFn>transitionValue);
   }
@@ -30,7 +29,7 @@ function parseInnerTransitionStr(
       expressions.push(result);
       return;
     }
-    eventStr = result as string;
+    eventStr = result;
   }
 
   const match = eventStr.match(/^(\*|[-\w]+)\s*(<?[=-]>)\s*(\*|[-\w]+)$/);

packages/animations/browser/src/render/transition_animation_engine.ts

@@ -1708,7 +1708,7 @@ function _flattenGroupPlayersRecur(players: AnimationPlayer[], finalPlayers: Ani
     if (player instanceof AnimationGroupPlayer) {
       _flattenGroupPlayersRecur(player.players, finalPlayers);
     } else {
-      finalPlayers.push(player as AnimationPlayer);
+      finalPlayers.push(player);
     }
   }
 }

packages/animations/browser/src/util.ts

@@ -26,7 +26,7 @@ export const NG_ANIMATING_SELECTOR = '.ng-animating';
 export function resolveTimingValue(value: string | number) {
   if (typeof value == 'number') return value;
 
-  const matches = (value as string).match(/^(-?[\.\d]+)(m?s)/);
+  const matches = value.match(/^(-?[\.\d]+)(m?s)/);
   if (!matches || matches.length < 2) return 0;
 
   return _convertTimeValueToMS(parseFloat(matches[1]), matches[2]);
@@ -73,7 +73,7 @@ function parseTimeExpression(
       easing = easingVal;
     }
   } else {
-    duration = <number>exp;
+    duration = exp;
   }
 
   if (!allowNegativeValues) {
@@ -214,10 +214,8 @@ const PARAM_REGEX =
 export function extractStyleParams(value: string | number): string[] {
   let params: string[] = [];
   if (typeof value === 'string') {
-    const val = value.toString();
-
     let match: any;
-    while (match = PARAM_REGEX.exec(val)) {
+    while (match = PARAM_REGEX.exec(value)) {
       params.push(match[1] as string);
     }
     PARAM_REGEX.lastIndex = 0;

packages/common/http/src/client.ts

@@ -457,7 +457,7 @@ export class HttpClient {
     if (first instanceof HttpRequest) {
       // It is. The other arguments must be undefined (per the signatures) and can be
       // ignored.
-      req = first as HttpRequest<any>;
+      req = first;
     } else {
       // It's a string, so it represents a URL. Construct a request based on it,
       // and incorporate the remaining arguments (assuming `GET` unless a method is
@@ -477,7 +477,7 @@ export class HttpClient {
         if (options.params instanceof HttpParams) {
           params = options.params;
         } else {
-          params = new HttpParams({ fromObject: options.params } as HttpParamsOptions);
+          params = new HttpParams({fromObject: options.params});
         }
       }
 
@@ -1798,7 +1798,7 @@ export class HttpClient {
   }): Observable<Blob>;
 
   /**
-   * Constructs a `PATCH` request that interprets the body as as a text string and
+   * Constructs a `PATCH` request that interprets the body as a text string and
    * returns the response as a string value.
    *
    * @param url The endpoint URL.

packages/common/src/i18n/localization.ts

@@ -94,9 +94,9 @@ export class NgLocaleLocalization extends NgLocalization {
 export function getPluralCase(locale: string, nLike: number | string): Plural {
   // TODO(vicb): lazy compute
   if (typeof nLike === 'string') {
-    nLike = parseInt(<string>nLike, 10);
+    nLike = parseInt(nLike, 10);
   }
-  const n: number = nLike as number;
+  const n: number = nLike;
   const nDecimal = n.toString().replace(/^[^.]*\.?/, '');
   const i = Math.floor(Math.abs(n));
   const v = nDecimal.length;

packages/common/src/pipes/deprecated/number_pipe.ts

@@ -50,7 +50,7 @@ function formatNumber(
     }
   }
 
-  return NumberFormatter.format(value as number, locale, style, {
+  return NumberFormatter.format(value, locale, style, {
     minimumIntegerDigits: minInt,
     minimumFractionDigits: minFraction,
     maximumFractionDigits: maxFraction,

packages/compiler-cli/src/diagnostics/typescript_symbols.ts

@@ -624,7 +624,7 @@ function findClassSymbolInContext(type: StaticSymbol, context: TypeContext): ts.
     // This handles a case where an <packageName>/index.d.ts and a <packageName>/<packageName>.d.ts
     // are in the same directory. If we are looking for <packageName>/<packageName> and didn't
     // find it, look for <packageName>/index.d.ts as the program might have found that instead.
-    const p = type.filePath as string;
+    const p = type.filePath;
     const m = p.match(INDEX_PATTERN);
     if (m) {
       const indexVersion = path.join(path.dirname(p), 'index.d.ts');

packages/compiler-cli/src/metadata/evaluator.ts

@@ -306,7 +306,7 @@ export class Evaluator {
                 error = propertyValue;
                 return true;  // Stop the forEachChild.
               } else {
-                obj[<string>propertyName] = isPropertyAssignment(assignment) ?
+                obj[propertyName] = isPropertyAssignment(assignment) ?
                     recordEntry(propertyValue, assignment.initializer) :
                     propertyValue;
               }
@@ -401,7 +401,7 @@ export class Evaluator {
           return recordEntry(member, node);
         }
         if (expression && this.isFoldable(propertyAccessExpression.expression))
-          return (<any>expression)[<string>member];
+          return (<any>expression)[member];
         if (isMetadataModuleReferenceExpression(expression)) {
           // A select into a module reference and be converted into a reference to the symbol
           // in the module

packages/compiler-cli/src/ngtsc/annotations/src/directive.ts

@@ -271,7 +271,7 @@ export function extractQueryMetadata(
   } else if (typeof arg === 'string') {
     predicate = [arg];
   } else if (isStringArrayOrDie(arg, '@' + name)) {
-    predicate = arg as string[];
+    predicate = arg;
   } else {
     throw new FatalDiagnosticError(
         ErrorCode.VALUE_HAS_WRONG_TYPE, node, `@${name} predicate cannot be interpreted`);

packages/compiler/src/metadata_resolver.ts

@@ -1012,18 +1012,19 @@ export class CompileMetadataResolver {
           return;
         } else {
           const providersInfo =
-              (<string[]>providers.reduce(
-                   (soFar: string[], seenProvider: any, seenProviderIdx: number) => {
-                     if (seenProviderIdx < providerIdx) {
-                       soFar.push(`${stringifyType(seenProvider)}`);
-                     } else if (seenProviderIdx == providerIdx) {
-                       soFar.push(`?${stringifyType(seenProvider)}?`);
-                     } else if (seenProviderIdx == providerIdx + 1) {
-                       soFar.push('...');
-                     }
-                     return soFar;
-                   },
-                   []))
+              providers
+                  .reduce(
+                      (soFar: string[], seenProvider: any, seenProviderIdx: number) => {
+                        if (seenProviderIdx < providerIdx) {
+                          soFar.push(`${stringifyType(seenProvider)}`);
+                        } else if (seenProviderIdx == providerIdx) {
+                          soFar.push(`?${stringifyType(seenProvider)}?`);
+                        } else if (seenProviderIdx == providerIdx + 1) {
+                          soFar.push('...');
+                        }
+                        return soFar;
+                      },
+                      [])
                   .join(', ');
           this._reportError(
               syntaxError(

packages/core/src/render3/node_selector_matcher.ts

@@ -81,7 +81,7 @@ export function isNodeMatchingSelector(
     const current = selector[i];
     if (typeof current === 'number') {
       // If we finish processing a :not selector and it hasn't failed, return false
-      if (!skipToNextSelector && !isPositive(mode) && !isPositive(current as number)) {
+      if (!skipToNextSelector && !isPositive(mode) && !isPositive(current)) {
         return false;
       }
       // If we are skipping to the next :not() and this mode flag is positive,

packages/core/src/render3/query.ts

@@ -195,7 +195,7 @@ class TQuery_ implements TQuery {
 
   private matchTNode(tView: TView, tNode: TNode): void {
     if (Array.isArray(this.metadata.predicate)) {
-      const localNames = this.metadata.predicate as string[];
+      const localNames = this.metadata.predicate;
       for (let i = 0; i < localNames.length; i++) {
         this.matchTNodeWithReadOption(tView, tNode, getIdxOfMatchingSelector(tNode, localNames[i]));
       }

packages/core/src/render3/util/attrs_utils.ts

@@ -73,9 +73,8 @@ export function setUpAttributes(renderer: Renderer3, native: RElement, attrs: TA
         }
       } else {
         isProc ?
-            (renderer as ProceduralRenderer3)
-                .setAttribute(native, attrName as string, attrVal as string) :
-            native.setAttribute(attrName as string, attrVal as string);
+            (renderer as ProceduralRenderer3).setAttribute(native, attrName, attrVal as string) :
+            native.setAttribute(attrName, attrVal as string);
       }
       i++;
     }

packages/core/src/render3/util/styling_utils.ts

@@ -397,7 +397,7 @@ export function normalizeIntoStylingMap(
 
   if (props) {
     for (let i = 0; i < props.length; i++) {
-      const prop = props[i] as string;
+      const prop = props[i];
       const newProp = normalizeProps ? hyphenate(prop) : prop;
       const value = allValuesTrue ? true : map ![prop];
       addItemToStylingMap(stylingMapArr, newProp, value, true);

packages/core/src/sanitization/bypass.ts

@@ -88,9 +88,8 @@ class SafeResourceUrlImpl extends SafeValueImpl implements SafeResourceUrl {
 }
 
 export function unwrapSafeValue(value: string | SafeValue): string {
-  return value instanceof SafeValueImpl ?
-      (value as SafeValueImpl).changingThisBreaksApplicationSecurity :
-      (value as string);
+  return value instanceof SafeValueImpl ? value.changingThisBreaksApplicationSecurity :
+                                          value as string;
 }
 
 
@@ -116,8 +115,7 @@ export function allowSanitizationBypassAndThrow(value: any, type: BypassType): b
 }
 
 export function getSanitizationBypassType(value: any): BypassType|null {
-  return value instanceof SafeValueImpl && (value as SafeValueImpl).getTypeName() as BypassType ||
-      null;
+  return value instanceof SafeValueImpl && value.getTypeName() as BypassType || null;
 }
 
 /**

packages/core/testing/src/async_fallback.ts

@@ -45,7 +45,7 @@ export function asyncFallback(fn: Function): (done: any) => any {
       }
       runInTestZone(fn, this, done, (err: any) => {
         if (typeof err === 'string') {
-          return done.fail(new Error(<string>err));
+          return done.fail(new Error(err));
         } else {
           done.fail(err);
         }

packages/forms/src/model.ts

@@ -48,11 +48,11 @@ function _find(control: AbstractControl, path: Array<string|number>| string, del
   if (path == null) return null;
 
   if (!(path instanceof Array)) {
-    path = (<string>path).split(delimiter);
+    path = path.split(delimiter);
   }
-  if (path instanceof Array && (path.length === 0)) return null;
+  if (path instanceof Array && path.length === 0) return null;
 
-  return (<Array<string|number>>path).reduce((v: AbstractControl | null, name) => {
+  return path.reduce((v: AbstractControl | null, name) => {
     if (v instanceof FormGroup) {
       return v.controls.hasOwnProperty(name as string) ? v.controls[name] : null;
     }