From 8e5f90af351e067ae1c6d00d45432e0ae30226c5 Mon Sep 17 00:00:00 2001
From: Boudewijn van Groos <boudewijn@vangroos.nl>
Date: Thu, 25 Mar 2021 15:39:59 +0100
Subject: [PATCH] refactor: add exclusion when using type guard (#6168)

---
 api_guard/dist/types/index.d.ts            |  4 ++--
 spec-dtslint/observables/partition-spec.ts | 14 +++++++++++++-
 src/internal/observable/partition.ts       |  4 ++--
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/api_guard/dist/types/index.d.ts b/api_guard/dist/types/index.d.ts
index 623893ae48..3255065f84 100644
--- a/api_guard/dist/types/index.d.ts
+++ b/api_guard/dist/types/index.d.ts
@@ -321,8 +321,8 @@ export declare function pairs(n: number | bigint | boolean | ((...args: any[]) =
 
 export declare type PartialObserver<T> = NextObserver<T> | ErrorObserver<T> | CompletionObserver<T>;
 
-export declare function partition<T, U extends T, A>(source: ObservableInput<T>, predicate: (this: A, value: T, index: number) => value is U, thisArg: A): [Observable<U>, Observable<T>];
-export declare function partition<T, U extends T>(source: ObservableInput<T>, predicate: (value: T, index: number) => value is U): [Observable<U>, Observable<T>];
+export declare function partition<T, U extends T, A>(source: ObservableInput<T>, predicate: (this: A, value: T, index: number) => value is U, thisArg: A): [Observable<U>, Observable<Exclude<T, U>>];
+export declare function partition<T, U extends T>(source: ObservableInput<T>, predicate: (value: T, index: number) => value is U): [Observable<U>, Observable<Exclude<T, U>>];
 export declare function partition<T, A>(source: ObservableInput<T>, predicate: (this: A, value: T, index: number) => boolean, thisArg: A): [Observable<T>, Observable<T>];
 export declare function partition<T>(source: ObservableInput<T>, predicate: (value: T, index: number) => boolean): [Observable<T>, Observable<T>];
 
diff --git a/spec-dtslint/observables/partition-spec.ts b/spec-dtslint/observables/partition-spec.ts
index 474c7cae62..3d6f5517c3 100644
--- a/spec-dtslint/observables/partition-spec.ts
+++ b/spec-dtslint/observables/partition-spec.ts
@@ -1,4 +1,4 @@
-import { of, partition } from 'rxjs';
+import { of, from, partition } from 'rxjs';
 
 it('should infer correctly', () => {
   const o = partition(of('a', 'b', 'c'), (value, index) => true); // $ExpectType [Observable<string>, Observable<string>]
@@ -9,6 +9,10 @@ it('should support a user-defined type guard', () => {
   const o = partition(of(1, 2, 3), (value: number): value is 1 => value === 1); // $ExpectType [Observable<1>, Observable<number>]
 });
 
+it('should support exclusion based on the user-defined type guard', () => {
+  const o = partition(from([1, 2] as const), (value: number): value is 1 => value === 1); // $ExpectType [Observable<1>, Observable<2>]
+});
+
 it('should enforce predicate', () => {
   const o = partition(of('a', 'b', 'c')); // $ExpectError
 });
@@ -27,6 +31,14 @@ it('should support this with type guard', () => {
   }, thisArg);
 });
 
+it('should support this with exclusion based on the user-defined type guard', () => {
+  const thisArg = { limit: 2 };
+  const a = partition(from([1, 2] as const), function (val): val is 1 { // $ExpectType [Observable<1>, Observable<2>]
+    const limit = this.limit; // $ExpectType number
+    return val < limit;
+  }, thisArg);
+});
+
 it('should support this with predicate', () => {
   const thisArg = { limit: 2 };
   const a = partition(of(1, 2, 3), function (val) { // $ExpectType [Observable<number>, Observable<number>]
diff --git a/src/internal/observable/partition.ts b/src/internal/observable/partition.ts
index 4d94e462c9..d617a43803 100644
--- a/src/internal/observable/partition.ts
+++ b/src/internal/observable/partition.ts
@@ -8,11 +8,11 @@ export function partition<T, U extends T, A>(
   source: ObservableInput<T>,
   predicate: (this: A, value: T, index: number) => value is U,
   thisArg: A
-): [Observable<U>, Observable<T>];
+): [Observable<U>, Observable<Exclude<T, U>>];
 export function partition<T, U extends T>(
   source: ObservableInput<T>,
   predicate: (value: T, index: number) => value is U
-): [Observable<U>, Observable<T>];
+): [Observable<U>, Observable<Exclude<T, U>>];
 
 export function partition<T, A>(
   source: ObservableInput<T>,