Repository navigation
generic type inference for boolean literals fails #19896
Description
TypeScript Version: 2.6.1
Code
function test<T>(x: T, f: (y: T) => void) { return x; }
let z: false = false;
test(z, x => { z = x; });
// ------------^
// [ts]
// Type 'boolean | undefined' is not assignable to type 'false | undefined'.
// Type 'true' is not assignable to type 'false | undefined'.Expected behavior:
z and x should be of the same type
Actual behavior:
x is being inferred as boolean instead of false
Activity
patsissons commentedon Nov 10, 2017
I'll try and test this in@nextwhen i get a chance, just trying to get this issue posted for now.confirmed on
2.7.0-dev.20171109:Proculopsis commentedon Nov 18, 2017
// let z: false = false;
let z: boolean = false;
Isn't this a compiler bug, letting you use 'false' as a type rather than 'boolean'?
patsissons commentedon Nov 18, 2017
typescript permits boolean literals as type declarators. this is particularly relevant in React development, since
falsemeans do not render anything, buttruecannot be rendered.RyanCavanaugh commentedon Nov 20, 2017
Mohamed Hegazy (@mhegazy) what is the inferred suggestion here?
Qwertiy commentedon Jul 11, 2020
Seems working fine on 3.9.2.
jakebailey commentedon Jul 9, 2023
Just looking at old issues; this was fixed back by #27042.