signature overloading breaking change?

[Artazor]

Looks like that in 1.7.5 overloading order became significant in some cases

1. specific first

declare class A {
    f(x:string): any;
    f(x:{[key: string]: any}): A;
}

var a: A;
var x = a.f("A") + 1;  // OK in both TS 1.7.5 and TS 1.5.3

2. specific second

declare class A {
    f(x:{[key: string]: any}): A;
    f(x:string): any;
}

var a: A;
var x = a.f("A") + 1; // Fails on TS 1.7.5 (Worked on 1.5.3). Inferred f result as A

Is it by design?

[ahejlsberg]

Yes, it is by design. Specifically, it is an effect of the change in #4074.

[RyanCavanaugh]

Overloading has always been order-sensitive -- the first signature that matches is the one that's selected.

Recommended fix would be to replace [key: string]: any with [key: string]: {}

[Artazor]

@ahejlsberg, @RyanCavanaugh - thank you for explanation