Microsoft/TypeScript
Vedi su GitHub`asserts` keyword does not enhance hoisted function type, works on functions assigned to a variable
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#41.232 aperta il 25 ott 2020
BugDomain: check: Control FlowHelp Wanted
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Descrizione
TypeScript Version: 4.0.2, 4.1.0-beta
Search Terms: asserts function
Code
interface LabelledFunction { label: string; }
function assignLabel(fn: () => unknown, label: string): asserts fn is LabelledFunction {
Object.assign(fn, { label });
}
function a() { }
assignLabel(a, 'a');
console.info(a.label); // Property 'label' does not exist on type '() => void'.(2339)
const b = function () { };
assignLabel(b, 'b');
console.info(b.label); // works as expected
const c = () => { };
assignLabel(c, 'c');
console.info(c.label); // works as expected
Expected behavior:
At least in runtime code coming after assignLabel(a, 'a');, a.label should be accessible.
Actual behavior:
Property 'label' does not exist on type '() => void'.(2339)
Playground Link: link