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Can't use is type asserting function as predicate parameter #19642
Description
TypeScript Version: 2.5.3 and 2.7.0-dev.20171101
Code
type T1 = { t: 1 };
type T2 = { t: 2 };
function isT1(x: any): x is T1 {
return x.t === 1;
}
function isT2(x: any): x is T2 {
return x.t === 2;
}
function f(p: typeof isT1 | typeof isT2) {
}
f(isT1);
f(isT2); // failsExpected behavior:
It compiles
Actual behavior:
Fails to compile:
Argument of type '(x: any) => x is T2' is not assignable to parameter of type '(x: any) => x is T1'.
Type predicate 'x is T2' is not assignable to 'x is T1'.
Type 'T2' is not assignable to type 'T1'.
Types of property 't' are incompatible.
Type '2' is not assignable to type '1'
Activity
Add test for #19642
typescript-bot commentedon Nov 16, 2017
Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.
Lazily compute signature type predicates (#17600)