@SuppressWarnings("unchecked")
	static <T, R> boolean trySubscribeScalarMap(Publisher<? extends T> source,
			CoreSubscriber<? super R> s,
			Function<? super T, ? extends Publisher<? extends R>> mapper,
			boolean fuseableExpected) {
		if (source instanceof Callable) {
			T t;

			try {
				t = ((Callable<? extends T>) source).call();
			}
			catch (Throwable e) {
				Operators.error(s, Operators.onOperatorError(e, s.currentContext()));
				return true;
			}

			if (t == null) {
				Operators.complete(s);
				return true;
			}

			Publisher<? extends R> p;

			try {
				p = Objects.requireNonNull(mapper.apply(t),
						"The mapper returned a null Publisher");
			}
			catch (Throwable e) {
				Operators.error(s, Operators.onOperatorError(null, e, t, s.currentContext()));
				return true;
			}

			if (p instanceof Callable) {
				R v;

				try {
					v = ((Callable<R>) p).call();
				}
				catch (Throwable e) {
					Operators.error(s, Operators.onOperatorError(null, e, t, s.currentContext()));
					return true;
				}

				if (v != null) {
					s.onSubscribe(Operators.scalarSubscription(s, v));
				}
				else {
					Operators.complete(s);
				}
			}
			else {
				if (!fuseableExpected || p instanceof Fuseable) {
					p.subscribe(s);
				}
				else {
					p.subscribe(new FluxHide.SuppressFuseableSubscriber<>(s));
				}
			}

			return true;
		}

		return false;
	}
@SuppressWarnings("unchecked")
	static <T, R> boolean trySubscribeScalarMap(Publisher<? extends T> source,
			CoreSubscriber<? super R> s,
			Function<? super T, ? extends Publisher<? extends R>> mapper,
			boolean fuseableExpected) {
		if (source instanceof Callable) {
			T t;

			try {
				t = ((Callable<? extends T>) source).call();
			}
			catch (Throwable e) {
				Operators.error(s, Operators.onOperatorError(e, s.currentContext()));
				return true;
			}

			if (t == null) {
				Operators.complete(s);
				return true;
			}

			Publisher<? extends R> p;

			try {
				p = Objects.requireNonNull(mapper.apply(t),
						"The mapper returned a null Publisher");
			}
			catch (Throwable e) {
				Operators.error(s, Operators.onOperatorError(null, e, t, s.currentContext()));
				return true;
			}

			if (p instanceof Callable) {
				R v;

				try {
					v = ((Callable<R>) p).call();
				}
				catch (Throwable e) {
					Operators.error(s, Operators.onOperatorError(null, e, t, s.currentContext()));
					return true;
				}

				if (v != null) {
					s.onSubscribe(Operators.scalarSubscription(s, v));
				}
				else {
					Operators.complete(s);
				}
			}
			else {
				if (!fuseableExpected || p instanceof Fuseable) {
					p.subscribe(s);
				}
				else {
					p.subscribe(new FluxHide.SuppressFuseableSubscriber<>(s));
				}
			}

			return true;
		}

		return false;
	}
@ SuppressWarnings ( "unchecked" ) static < T , R > boolean trySubscribeScalarMap ( Publisher < ? extends T > source , CoreSubscriber < ? super R > s , Function < ? super T , ? extends Publisher < ? extends R > > mapper , boolean fuseableExpected ) { if ( source instanceof Callable ) { T t ; try { t = ( ( Callable < ? extends T > ) source ) . call ( ) ; } catch ( Throwable e ) { Operators . error ( s , Operators . onOperatorError ( e , s . currentContext ( ) ) ) ; return true ; } if ( t == null ) { Operators . complete ( s ) ; return true ; } Publisher < ? extends R > p ; try { p = Objects . requireNonNull ( mapper . apply ( t ) , "The mapper returned a null Publisher" ) ; } catch ( Throwable e ) { Operators . error ( s , Operators . onOperatorError ( null , e , t , s . currentContext ( ) ) ) ; return true ; } if ( p instanceof Callable ) { R v ; try { v = ( ( Callable < R > ) p ) . call ( ) ; } catch ( Throwable e ) { Operators . error ( s , Operators . onOperatorError ( null , e , t , s . currentContext ( ) ) ) ; return true ; } if ( v != null ) { s . onSubscribe ( Operators . scalarSubscription ( s , v ) ) ; } else { Operators . complete ( s ) ; } } else { if ( ! fuseableExpected || p instanceof Fuseable ) { p . subscribe ( s ) ; } else { p . subscribe ( new FluxHide . SuppressFuseableSubscriber <> ( s ) ) ; } } return true ; } return false ; }
Checks if the source is a Supplier and if the mapper's publisher output is also
a supplier, thus avoiding subscribing to any of them.

@param source the source publisher
@param s the end consumer
@param mapper the mapper function
@param fuseableExpected if true, the parent class was marked Fuseable thus the
mapping output has to signal onSubscribe with a QueueSubscription

@return true if the optimization worked
Checks if the source is a Supplier and if the mapper s publisher output is also a supplier thus avoiding subscribing to any of them .