Function overloading, problem with arguments

Question

In this code declaring several overloading functions:

export function rect(a: Point, b: Point): Rect;
export function rect(a: Point, b: number|Point, c?: number): Rect;
export function rect(a: number|Point, b: number|Point, c?: number, d?: number ) {return new Rect(a,b,c,d);}
rect( 1,1,1, 1)   // ts: "Expected 2-3 arguments, but got 4.ts(2554)"

Typescript complains in the 4th arg. I couldn't figure what is wrong here. If I add one more overload with one more arg:

export function rect(a: Point, b: Point): Rect;
export function rect(a: Point, b: number|Point, c?: number): Rect;
export function rect(a: number|Point, b: number|Point, c?: number, d?: number ): Rect ;
export function rect(a: number|Point, b: number|Point, c?: number, d?: number, e?: number ): Rect {return new Rect(a,b,c,d);}
rect( 1,1,1, 1)

ts does NOT complain (it gives the same error if I add the 5th arg to the call to rect)

What's wrong?

Function implementation must meet all overload deninitions. If you need more parameteres, add another overload — Alexander Vidaurre Arroyo
– Alexander Vidaurre Arroyo, Commented Jan 6, 2020 at 21:53

Titian Cernicova-Dragomir · Accepted Answer · 2020-01-06 21:51:19Z

1

The last overload signature is the implementation signature and is not visible to the outside. If you want to have that interface public you will need to duplicate it:

export function rect(a: Point, b: Point): Rect;
export function rect(a: Point, b: number | Point, c?: number): Rect;
export function rect(a: number | Point, b: number | Point, c?: number, d?: number): Rect;
export function rect(a: number | Point, b: number | Point, c?: number, d?: number) {
    return new Rect(a, b, c, d);
}

answered Jan 6, 2020 at 21:51

Titian Cernicova-Dragomir

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