fix: operators that ignore input values now use unknown rather than…

… `any`, which should resolve issues with eslint no-unsafe-argument (#6738)

* fix: use "unknown" type for operators that ignore input values

These operators ignore the values produced by the source Observable, so
they don't need the dynamic typing that "any" would provide for
accessing the values.  Using "unknown" instead of "any" avoids warnings
from eslint rules like @typescript-eslint/no-unsafe-argument in
application code that uses the operators, and it's also a clearer way to
express that the operators don't know or care what the source type is.

resolves #6536

* fix: update api_guard files to reflect intentional API change

api_guard/dist/types/index.d.ts

@@ -108,8 +108,8 @@ export declare function concatMap<T, O extends ObservableInput<any>>(project: (v
 export declare function concatMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined): OperatorFunction<T, ObservedValueOf<O>>;
 export declare function concatMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
 
-export declare function concatMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<any, ObservedValueOf<O>>;
-export declare function concatMapTo<O extends ObservableInput<unknown>>(observable: O, resultSelector: undefined): OperatorFunction<any, ObservedValueOf<O>>;
+export declare function concatMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<unknown, ObservedValueOf<O>>;
+export declare function concatMapTo<O extends ObservableInput<unknown>>(observable: O, resultSelector: undefined): OperatorFunction<unknown, ObservedValueOf<O>>;
 export declare function concatMapTo<T, R, O extends ObservableInput<unknown>>(observable: O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
 
 export declare function concatWith<T, A extends readonly unknown[]>(...otherSources: [...ObservableInputTuple<A>]): OperatorFunction<T, T | A[number]>;
@@ -314,7 +314,7 @@ export declare type Head<X extends readonly any[]> = ((...args: X) => any) exten
 
 export declare function identity<T>(x: T): T;
 
-export declare function ignoreElements(): OperatorFunction<any, never>;
+export declare function ignoreElements(): OperatorFunction<unknown, never>;
 
 export declare function iif<T, F>(condition: () => boolean, trueResult: ObservableInput<T>, falseResult: ObservableInput<F>): Observable<T | F>;
 
@@ -340,7 +340,7 @@ export declare function lastValueFrom<T>(source: Observable<T>): Promise<T>;
 export declare function map<T, R>(project: (value: T, index: number) => R): OperatorFunction<T, R>;
 export declare function map<T, R, A>(project: (this: A, value: T, index: number) => R, thisArg: A): OperatorFunction<T, R>;
 
-export declare function mapTo<R>(value: R): OperatorFunction<any, R>;
+export declare function mapTo<R>(value: R): OperatorFunction<unknown, R>;
 export declare function mapTo<T, R>(value: R): OperatorFunction<T, R>;
 
 export declare function materialize<T>(): OperatorFunction<T, Notification<T> & ObservableNotification<T>>;
@@ -358,7 +358,7 @@ export declare function mergeMap<T, O extends ObservableInput<any>>(project: (va
 export declare function mergeMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined, concurrent?: number): OperatorFunction<T, ObservedValueOf<O>>;
 export declare function mergeMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R, concurrent?: number): OperatorFunction<T, R>;
 
-export declare function mergeMapTo<O extends ObservableInput<unknown>>(innerObservable: O, concurrent?: number): OperatorFunction<any, ObservedValueOf<O>>;
+export declare function mergeMapTo<O extends ObservableInput<unknown>>(innerObservable: O, concurrent?: number): OperatorFunction<unknown, ObservedValueOf<O>>;
 export declare function mergeMapTo<T, R, O extends ObservableInput<unknown>>(innerObservable: O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R, concurrent?: number): OperatorFunction<T, R>;
 
 export declare function mergeScan<T, R>(accumulator: (acc: R, value: T, index: number) => ObservableInput<R>, seed: R, concurrent?: number): OperatorFunction<T, R>;
@@ -729,8 +729,8 @@ export declare function switchMap<T, O extends ObservableInput<any>>(project: (v
 export declare function switchMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined): OperatorFunction<T, ObservedValueOf<O>>;
 export declare function switchMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
 
-export declare function switchMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<any, ObservedValueOf<O>>;
-export declare function switchMapTo<O extends ObservableInput<unknown>>(observable: O, resultSelector: undefined): OperatorFunction<any, ObservedValueOf<O>>;
+export declare function switchMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<unknown, ObservedValueOf<O>>;
+export declare function switchMapTo<O extends ObservableInput<unknown>>(observable: O, resultSelector: undefined): OperatorFunction<unknown, ObservedValueOf<O>>;
 export declare function switchMapTo<T, R, O extends ObservableInput<unknown>>(observable: O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
 
 export declare function switchScan<T, R, O extends ObservableInput<any>>(accumulator: (acc: R, value: T, index: number) => O, seed: R): OperatorFunction<T, ObservedValueOf<O>>;

api_guard/dist/types/operators/index.d.ts

@@ -45,8 +45,8 @@ export declare function concatMap<T, O extends ObservableInput<any>>(project: (v
 export declare function concatMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined): OperatorFunction<T, ObservedValueOf<O>>;
 export declare function concatMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
 
-export declare function concatMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<any, ObservedValueOf<O>>;
-export declare function concatMapTo<O extends ObservableInput<unknown>>(observable: O, resultSelector: undefined): OperatorFunction<any, ObservedValueOf<O>>;
+export declare function concatMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<unknown, ObservedValueOf<O>>;
+export declare function concatMapTo<O extends ObservableInput<unknown>>(observable: O, resultSelector: undefined): OperatorFunction<unknown, ObservedValueOf<O>>;
 export declare function concatMapTo<T, R, O extends ObservableInput<unknown>>(observable: O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
 
 export declare function concatWith<T, A extends readonly unknown[]>(...otherSources: [...ObservableInputTuple<A>]): OperatorFunction<T, T | A[number]>;
@@ -144,7 +144,7 @@ export interface GroupByOptionsWithElement<K, E, T> {
     element: (value: T) => E;
 }
 
-export declare function ignoreElements(): OperatorFunction<any, never>;
+export declare function ignoreElements(): OperatorFunction<unknown, never>;
 
 export declare function isEmpty<T>(): OperatorFunction<T, boolean>;
 
@@ -157,7 +157,7 @@ export declare function last<T, D = T>(predicate: (value: T, index: number, sour
 export declare function map<T, R>(project: (value: T, index: number) => R): OperatorFunction<T, R>;
 export declare function map<T, R, A>(project: (this: A, value: T, index: number) => R, thisArg: A): OperatorFunction<T, R>;
 
-export declare function mapTo<R>(value: R): OperatorFunction<any, R>;
+export declare function mapTo<R>(value: R): OperatorFunction<unknown, R>;
 export declare function mapTo<T, R>(value: R): OperatorFunction<T, R>;
 
 export declare function materialize<T>(): OperatorFunction<T, Notification<T> & ObservableNotification<T>>;
@@ -175,7 +175,7 @@ export declare function mergeMap<T, O extends ObservableInput<any>>(project: (va
 export declare function mergeMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined, concurrent?: number): OperatorFunction<T, ObservedValueOf<O>>;
 export declare function mergeMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R, concurrent?: number): OperatorFunction<T, R>;
 
-export declare function mergeMapTo<O extends ObservableInput<unknown>>(innerObservable: O, concurrent?: number): OperatorFunction<any, ObservedValueOf<O>>;
+export declare function mergeMapTo<O extends ObservableInput<unknown>>(innerObservable: O, concurrent?: number): OperatorFunction<unknown, ObservedValueOf<O>>;
 export declare function mergeMapTo<T, R, O extends ObservableInput<unknown>>(innerObservable: O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R, concurrent?: number): OperatorFunction<T, R>;
 
 export declare function mergeScan<T, R>(accumulator: (acc: R, value: T, index: number) => ObservableInput<R>, seed: R, concurrent?: number): OperatorFunction<T, R>;
@@ -300,8 +300,8 @@ export declare function switchMap<T, O extends ObservableInput<any>>(project: (v
 export declare function switchMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined): OperatorFunction<T, ObservedValueOf<O>>;
 export declare function switchMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
 
-export declare function switchMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<any, ObservedValueOf<O>>;
-export declare function switchMapTo<O extends ObservableInput<unknown>>(observable: O, resultSelector: undefined): OperatorFunction<any, ObservedValueOf<O>>;
+export declare function switchMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<unknown, ObservedValueOf<O>>;
+export declare function switchMapTo<O extends ObservableInput<unknown>>(observable: O, resultSelector: undefined): OperatorFunction<unknown, ObservedValueOf<O>>;
 export declare function switchMapTo<T, R, O extends ObservableInput<unknown>>(observable: O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
 
 export declare function switchScan<T, R, O extends ObservableInput<any>>(accumulator: (acc: R, value: T, index: number) => O, seed: R): OperatorFunction<T, ObservedValueOf<O>>;

src/internal/operators/concatMapTo.ts

@@ -3,12 +3,12 @@ import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
 import { isFunction } from '../util/isFunction';
 
 /* tslint:disable:max-line-length */
-export function concatMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<any, ObservedValueOf<O>>;
+export function concatMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<unknown, ObservedValueOf<O>>;
 /** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
 export function concatMapTo<O extends ObservableInput<unknown>>(
   observable: O,
   resultSelector: undefined
-): OperatorFunction<any, ObservedValueOf<O>>;
+): OperatorFunction<unknown, ObservedValueOf<O>>;
 /** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
 export function concatMapTo<T, R, O extends ObservableInput<unknown>>(
   observable: O,

src/internal/operators/ignoreElements.ts

@@ -38,7 +38,7 @@ import { noop } from '../util/noop';
  * `complete` or `error`, based on which one is called by the source
  * Observable.
  */
-export function ignoreElements(): OperatorFunction<any, never> {
+export function ignoreElements(): OperatorFunction<unknown, never> {
   return operate((source, subscriber) => {
     source.subscribe(new OperatorSubscriber(subscriber, noop));
   });

src/internal/operators/mapTo.ts

@@ -1,7 +1,7 @@
 import { OperatorFunction } from '../types';
 import { map } from './map';
 
-export function mapTo<R>(value: R): OperatorFunction<any, R>;
+export function mapTo<R>(value: R): OperatorFunction<unknown, R>;
 /** @deprecated Do not specify explicit type parameters. Signatures with type parameters that cannot be inferred will be removed in v8. */
 export function mapTo<T, R>(value: R): OperatorFunction<T, R>;
 
@@ -37,6 +37,6 @@ export function mapTo<T, R>(value: R): OperatorFunction<T, R>;
  * @return A function that returns an Observable that emits the given `value`
  * every time the source Observable emits.
  */
-export function mapTo<R>(value: R): OperatorFunction<any, R> {
+export function mapTo<R>(value: R): OperatorFunction<unknown, R> {
   return map(() => value);
 }

src/internal/operators/mergeMapTo.ts

@@ -6,7 +6,7 @@ import { isFunction } from '../util/isFunction';
 export function mergeMapTo<O extends ObservableInput<unknown>>(
   innerObservable: O,
   concurrent?: number
-): OperatorFunction<any, ObservedValueOf<O>>;
+): OperatorFunction<unknown, ObservedValueOf<O>>;
 /** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
 export function mergeMapTo<T, R, O extends ObservableInput<unknown>>(
   innerObservable: O,

src/internal/operators/switchMapTo.ts

@@ -3,12 +3,12 @@ import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
 import { isFunction } from '../util/isFunction';
 
 /* tslint:disable:max-line-length */
-export function switchMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<any, ObservedValueOf<O>>;
+export function switchMapTo<O extends ObservableInput<unknown>>(observable: O): OperatorFunction<unknown, ObservedValueOf<O>>;
 /** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
 export function switchMapTo<O extends ObservableInput<unknown>>(
   observable: O,
   resultSelector: undefined
-): OperatorFunction<any, ObservedValueOf<O>>;
+): OperatorFunction<unknown, ObservedValueOf<O>>;
 /** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
 export function switchMapTo<T, R, O extends ObservableInput<unknown>>(
   observable: O,