Function overloads don't play nice with unions of string literals

[fongandrew]

TypeScript Version: 2.3.2

Code

function test(a: "A"): any;
function test(b: "B"): any;
function test(ab: "A"|"B"): any { }

declare var u: "A"|"B";
test(u);

Expected behavior: No error

Actual behavior: Argument of type "A"|"B" is not assignable to type "B"

Ideally, TypeScript should detect that there is an overload for each variant of the union type and thus accept the union type as an argument.

[RyanCavanaugh]

Duplicate #14107

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.