fix(TS): fix type inference for publish variants

- We can never get  out of  via TypeScript any how.
- Resolves a larger issue where operators with a single, static argument and a single  generic inferred too strongly from the argument and lost the additional type information from the source.

compat/operator/publishBehavior.ts

@@ -8,5 +8,5 @@ import { publishBehavior as higherOrder } from 'rxjs/operators';
  * @owner Observable
  */
 export function publishBehavior<T>(this: Observable<T>, value: T): ConnectableObservable<T> {
-  return higherOrder(value)(this);
+  return higherOrder(value)(this) as ConnectableObservable<T>;
 }

package.json

@@ -215,7 +215,7 @@
     "tslint-etc": "1.5.0",
     "tslint-no-toplevel-property-access": "0.0.2",
     "tslint-no-unused-expression-chai": "0.0.3",
-    "typescript": "^3.0.1",
+    "typescript": "^3.4.5",
     "validate-commit-msg": "2.14.0",
     "webpack": "^4.31.0"
   },

spec-dtslint/operators/publish-spec.ts

@@ -2,11 +2,7 @@ import { of, Observable } from 'rxjs';
 import { publish } from 'rxjs/operators';
 
 it('should support empty parameter', () => {
-  // Here, TypeScript versions 3.1 and earlier infer Observable<any>. However,
-  // the next version infers Observable<number>. It's not possible to specify
-  // an upper bound for the TypeScript version used by dtslint, so an
-  // expectation cannot be applied.
-  const a = of(1, 2, 3).pipe(publish()); // $ExpectType Observable<any>
+  const a = of(1, 2, 3).pipe(publish()); // $ExpectType Observable<number>
 });
 
 it('should infer when type is specified', () => {

spec-dtslint/operators/publishBehavior-spec.ts

@@ -1,5 +1,5 @@
 import { of } from 'rxjs';
-import { publishBehavior } from 'rxjs/operators';
+import { publishBehavior, map } from 'rxjs/operators';
 
 it('should enforce parameter', () => {
   const a = of(1, 2, 3).pipe(publishBehavior()); // $ExpectError
@@ -10,5 +10,10 @@ it('should infer correctly with parameter', () => {
 });
 
 it('should enforce type on parameter', () => {
-  const a = of(1, 2, 3).pipe(publishBehavior('a'); // $ExpectError
+  const a = of(1, 2, 3).pipe(publishBehavior('a')); // $ExpectType Observable<string | number>
+});
+
+it('should compose properly', () => {
+  const fn = () => Math.random() > 0.5;
+  const a = of(true, false).pipe(map(x => x && fn()), publishBehavior(false)); // $ExpectType Observable<boolean>
 });

spec-dtslint/operators/publishLast-spec.ts

@@ -2,11 +2,7 @@ import { of } from 'rxjs';
 import { publishLast } from 'rxjs/operators';
 
 it('should accept empty parameter', () => {
-  // Here, TypeScript versions 3.1 and earlier infer Observable<any>. However,
-  // the next version infers Observable<number>. It's not possible to specify
-  // an upper bound for the TypeScript version used by dtslint, so an
-  // expectation cannot be applied.
-  const a = of(1, 2, 3).pipe(publishLast()); // $ExpectType Observable<any>
+  const a = of(1, 2, 3).pipe(publishLast()); // $ExpectType Observable<number>
 });
 
 it('should infer when type is specified', () => {

spec/operators/multicast-spec.ts

@@ -703,49 +703,4 @@ describe('multicast operator', () => {
         });
     });
   });
-
-  describe('typings', () => {
-    type('should infer the type', () => {
-      /* tslint:disable:no-unused-variable */
-      const source = of<number>(1, 2, 3);
-      const result: ConnectableObservable<number> = source.pipe(multicast(() => new Subject<number>())) as ConnectableObservable<number>;
-      /* tslint:enable:no-unused-variable */
-    });
-
-    type('should infer the type with a selector', () => {
-      /* tslint:disable:no-unused-variable */
-      const source = of<number>(1, 2, 3);
-      const result: Observable<number> = source.pipe(multicast(() => new Subject<number>(), s => s.pipe(map(x => x))));
-      /* tslint:enable:no-unused-variable */
-    });
-
-    type('should infer the type with a type-changing selector', () => {
-      /* tslint:disable:no-unused-variable */
-      const source = of<number>(1, 2, 3);
-      const result: Observable<string> = source.pipe(multicast(() => new Subject<number>(), s => s.pipe(map(x => x + '!'))));
-      /* tslint:enable:no-unused-variable */
-    });
-
-    type('should infer the type for the pipeable operator', () => {
-      /* tslint:disable:no-unused-variable */
-      const source = of<number>(1, 2, 3);
-      // TODO: https://github.com/ReactiveX/rxjs/issues/2972
-      const result: ConnectableObservable<number> = multicast(() => new Subject<number>())(source);
-      /* tslint:enable:no-unused-variable */
-    });
-
-    type('should infer the type for the pipeable operator with a selector', () => {
-      /* tslint:disable:no-unused-variable */
-      const source = of<number>(1, 2, 3);
-      const result: Observable<number> = source.pipe(multicast(() => new Subject<number>(), s => s.pipe(map(x => x))));
-      /* tslint:enable:no-unused-variable */
-    });
-
-    type('should infer the type for the pipeable operator with a type-changing selector', () => {
-      /* tslint:disable:no-unused-variable */
-      const source = of<number>(1, 2, 3);
-      const result: Observable<string> = source.pipe(multicast(() => new Subject<number>(), s => s.pipe(map(x => x + '!'))));
-      /* tslint:enable:no-unused-variable */
-    });
-  });
 });

src/internal/operators/multicast.ts

@@ -3,12 +3,12 @@ import { Operator } from '../Operator';
 import { Subscriber } from '../Subscriber';
 import { Observable } from '../Observable';
 import { ConnectableObservable, connectableObservableDescriptor } from '../observable/ConnectableObservable';
-import { OperatorFunction, UnaryFunction, ObservedValueOf, ObservableInput } from '../types';
+import { OperatorFunction, UnaryFunction, ObservedValueOf, ObservableInput, MonoTypeOperatorFunction } from '../types';
 
 /* tslint:disable:max-line-length */
-export function multicast<T>(subject: Subject<T>): UnaryFunction<Observable<T>, ConnectableObservable<T>>;
-export function multicast<T, O extends ObservableInput<any>>(subject: Subject<T>, selector: (shared: Observable<T>) => O): UnaryFunction<Observable<T>, ConnectableObservable<ObservedValueOf<O>>>;
-export function multicast<T>(subjectFactory: (this: Observable<T>) => Subject<T>): UnaryFunction<Observable<T>, ConnectableObservable<T>>;
+export function multicast<T>(subject: Subject<T>): MonoTypeOperatorFunction<T>;
+export function multicast<T, O extends ObservableInput<any>>(subject: Subject<T>, selector: (shared: Observable<T>) => O): OperatorFunction<T, ObservedValueOf<O>>;
+export function multicast<T>(subjectFactory: (this: Observable<T>) => Subject<T>): MonoTypeOperatorFunction<T>;
 export function multicast<T, O extends ObservableInput<any>>(SubjectFactory: (this: Observable<T>) => Subject<T>, selector: (shared: Observable<T>) => O): OperatorFunction<T, ObservedValueOf<O>>;
 /* tslint:enable:max-line-length */
 

src/internal/operators/publish.ts

@@ -5,7 +5,7 @@ import { ConnectableObservable } from '../observable/ConnectableObservable';
 import { MonoTypeOperatorFunction, OperatorFunction, UnaryFunction, ObservableInput, ObservedValueOf } from '../types';
 
 /* tslint:disable:max-line-length */
-export function publish<T>(): UnaryFunction<Observable<T>, ConnectableObservable<T>>;
+export function publish<T>(): MonoTypeOperatorFunction<T>;
 export function publish<T, O extends ObservableInput<any>>(selector: (shared: Observable<T>) => O): OperatorFunction<T, ObservedValueOf<O>>;
 export function publish<T>(selector: MonoTypeOperatorFunction<T>): MonoTypeOperatorFunction<T>;
 /* tslint:enable:max-line-length */

src/internal/operators/publishBehavior.ts

@@ -1,15 +1,21 @@
 import { Observable } from '../Observable';
 import { BehaviorSubject } from '../BehaviorSubject';
 import { multicast } from './multicast';
-import { ConnectableObservable } from '../observable/ConnectableObservable';
-import { UnaryFunction } from '../types';
+import { OperatorFunction } from '../types';
 
 /**
- * @param value
+ * Multicasts the observable source through an underlying {@link BehaviorSubject}. All subscriptions
+ * to the resulting observable will subscribe to the underlaying `BehaviorSubject`, the
+ * resulting observable is a {@link ConnectableObservable}. If you call `connect()` on that observable
+ * (requires a cast to `ConnectableObservable` in TypeScript), it will subscribe to the source
+ * observable with the underlying subject and connect that source too all consumers subscribed through the
+ * subject. Because it's using a `BehaviorSubject`, all new subscriptions will get the most recent value
+ * that has passed through said subject, _or_ they will get the `initialValue` if no values have
+ * arrived yet, so long as the published `ConnectableObservable` has been connected.
+ *
+ * @param initialValue
  * @return {ConnectableObservable<T>}
- * @method publishBehavior
- * @owner Observable
  */
-export function publishBehavior<T>(value: T):  UnaryFunction<Observable<T>, ConnectableObservable<T>> {
-  return (source: Observable<T>) => multicast(new BehaviorSubject<T>(value))(source) as ConnectableObservable<T>;
+export function publishBehavior<T, D>(initialValue: D): OperatorFunction<T, T | D> {
+  return (source: Observable<T>) => multicast(new BehaviorSubject<T | D>(initialValue))(source);
 }

src/internal/operators/publishLast.ts

@@ -2,7 +2,7 @@ import { Observable } from '../Observable';
 import { AsyncSubject } from '../AsyncSubject';
 import { multicast } from './multicast';
 import { ConnectableObservable } from '../observable/ConnectableObservable';
-import { UnaryFunction } from '../types';
+import { UnaryFunction, MonoTypeOperatorFunction } from '../types';
 
 /**
  * Returns a connectable observable sequence that shares a single subscription to the
@@ -62,6 +62,6 @@ import { UnaryFunction } from '../types';
  * @owner Observable
  */
 
-export function publishLast<T>(): UnaryFunction<Observable<T>, ConnectableObservable<T>> {
+export function publishLast<T>(): MonoTypeOperatorFunction<T> {
   return (source: Observable<T>) => multicast(new AsyncSubject<T>())(source);
 }