TypeScript: Can I provide a type alias for an overloaded function signature? -

is possible create type alias overloaded function signature?

for example, have function like:

function whenchanged(scope: ng.iscope, fn: ()=>void): ()=>void; function whenchanged(fn: ()=>void, truthy:any): ()=>void; function whenchanged(a,b): ()=>void {     //... } 

i create type alias overloaded signature save repetition, , make use of in other places need describe type of function.

i tried:

type wc1 = (scope: ng.iscope, fn: ()=>void) => ()=>void; type wc2 = (fn: ()=>void, truthy:any) => ()=>void; type whenchanged = wc1 | wc2;  const whenchanged: whenchanged = (a,b) => {     //... }; 

but trying use function, error along lines of "cannot invoke expression type lacks call signature".

i cannot offhand see in docs type aliasing function overloads.

since have function whenchanged:

function whenchanged(scope: ng.iscope, fn: ()=>void): ()=>void; function whenchanged(fn: ()=>void, truthy:any): ()=>void; function whenchanged(a,b): ()=>void {     //... } 

the simplest way type alias type use typeof type query:

type whenchanged = typeof whenchanged; 

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the next, straightforward way create type alias use overloaded function signature (which looking for):

type whenchanged = {   (scope: ng.iscope, fn: () => void): () => void;   (fn: () => void, truthy: any): () => void; } 

(which see in quickinfo if hover on typeof definition in editor.) note don't need use interface if don't want to.

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the next thing similar doing, problem overload intersection, not union. both signatures:

type wc1 = (scope: ng.iscope, fn: ()=>void) => ()=>void; type wc2 = (fn: ()=>void, truthy:any) => ()=>void; type whenchanged = wc1 & wc2; // and, not or 

be careful intersections of function signatures not commutative, because represent overloads. means following type not technically same:

type notwhenchanged = wc2 & wc1; // different type 

since overload resolution take place in different order.

note can't call function of type wc1 | wc2 since call signatures different compiler can't tell if function wc1 or wc2.

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okay, there go. hope helps; luck!