Merge pull request #2119 from rob3c/fix-type-guard-propagation

feat(filter, find, first, last): support type guard predicates that don't requiring casting

Author: kwonoj

src/operator/filter.ts

@@ -44,9 +44,10 @@ import { TeardownLogic } from '../Subscription';
  * @owner Observable
  */
 /* tslint:disable:max-line-length */
-export function filter<T>(this: Observable<T>, predicate: (value: T, index: number) => boolean, thisArg?: any): Observable<T>;
-export function filter<T, S extends T>(this: Observable<T>, predicate: (value: T, index: number) => value is S, thisArg?: any): Observable<S>;
-/* tslint:disable:max-line-length */
+export function filter<T, S extends T>(this: Observable<T>,
+                                       predicate: ((value: T, index: number) => boolean) |
+                                                  ((value: T, index: number) => value is S),
+                                       thisArg?: any): Observable<S>;
 export function filter<T>(this: Observable<T>, predicate: (value: T, index: number) => boolean,
                           thisArg?: any): Observable<T> {
   return this.lift(new FilterOperator(predicate, thisArg));

src/operator/find.ts

@@ -36,8 +36,10 @@ import { Subscriber } from '../Subscriber';
  * @owner Observable
  */
 /* tslint:disable:max-line-length */
-export function find<T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any): Observable<T>;
-export function find<T, S extends T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => value is S, thisArg?: any): Observable<S>;
+export function find<T, S extends T>(this: Observable<T>,
+                                     predicate: ((value: T, index: number, source: Observable<T>) => boolean) |
+                                                ((value: T, index: number, source: Observable<T>) => value is S),
+                                     thisArg?: any): Observable<S>;
 /* tslint:disable:max-line-length */
 export function find<T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => boolean,
                         thisArg?: any): Observable<T> {

src/operator/first.ts

@@ -53,10 +53,15 @@ import { EmptyError } from '../util/EmptyError';
  * @owner Observable
  */
 /* tslint:disable:max-line-length */
-export function first<T>(this: Observable<T>, predicate?: (value: T, index: number, source: Observable<T>) => boolean): Observable<T>;
-export function first<T, S extends T>(this: Observable<T>, predicate?: (value: T, index: number, source: Observable<T>) => value is S): Observable<S>;
+export function first<T, S extends T>(this: Observable<T>,
+                                      predicate?: ((value: T, index: number, source: Observable<T>) => boolean) |
+                                                  ((value: T, index: number, source: Observable<T>) => value is S)): Observable<S>;
 export function first<T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => boolean, resultSelector: void, defaultValue?: T): Observable<T>;
-export function first<T, S extends T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => value is S, resultSelector: void, defaultValue?: S): Observable<S>;
+export function first<T, S extends T, R>(this: Observable<T>,
+                                         predicate: ((value: T, index: number, source: Observable<T>) => boolean) |
+                                                    ((value: T, index: number, source: Observable<T>) => value is S),
+                                         resultSelector?: ((value: S, index: number) => R) | void,
+                                         defaultValue?: S): Observable<S>;
 export function first<T, R>(this: Observable<T>, predicate?: (value: T, index: number, source: Observable<T>) => boolean, resultSelector?: (value: T, index: number) => R, defaultValue?: R): Observable<R>;
 /* tslint:disable:max-line-length */
 export function first<T, R>(this: Observable<T>, predicate?: (value: T, index: number, source: Observable<T>) => boolean,

src/operator/last.ts

@@ -21,10 +21,15 @@ import { EmptyError } from '../util/EmptyError';
  * @owner Observable
  */
 /* tslint:disable:max-line-length */
-export function last<T>(this: Observable<T>, predicate?: (value: T, index: number, source: Observable<T>) => boolean): Observable<T>;
-export function last<T, S extends T>(this: Observable<T>, predicate?: (value: T, index: number, source: Observable<T>) => value is S): Observable<S>;
+export function last<T, S extends T>(this: Observable<T>,
+                                     predicate?: ((value: T, index: number, source: Observable<T>) => boolean) |
+                                                 ((value: T, index: number, source: Observable<T>) => value is S)): Observable<S>;
 export function last<T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => boolean, resultSelector: void, defaultValue?: T): Observable<T>;
-export function last<T, S extends T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => value is S, resultSelector: void, defaultValue?: S): Observable<S>;
+export function last<T, S extends T, R>(this: Observable<T>,
+                                        predicate: ((value: T, index: number, source: Observable<T>) => boolean) |
+                                                   ((value: T, index: number, source: Observable<T>) => value is S),
+                                        resultSelector?: ((value: S, index: number) => R) | void,
+                                        defaultValue?: S): Observable<S>;
 export function last<T, R>(this: Observable<T>, predicate?: (value: T, index: number, source: Observable<T>) => boolean, resultSelector?: (value: T, index: number) => R, defaultValue?: R): Observable<R>;
 /* tslint:disable:max-line-length */
 export function last<T, R>(this: Observable<T>, predicate?: (value: T, index: number, source: Observable<T>) => boolean,