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No way to get generic type of an abstract class inside a factory function #35576
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I have to add that if in classFactory2 the return statement is changed to
return ACS as typeof ACS & {prototype: typeof ACS }Then oddly enough the "InstanceViaNew" works, yet "InstanceViaProto" still doesn't (I'd have expected the opposite)
InstanceViaProtoought to work here; we're probably failing to apply the type mapper in the right place?Ron Buckton (@rbuckton) I think the PR will certainly make InstanceViaNew work (nice!), but I guess it wouldn't fix the InstanceViaProto case?
Also I found out that if you do something like this:
function classFactory2<T>() { abstract class ACS { constructor(_y: number) {} x!: T } return ACS } const ACS = classFactory2<string>() // this doesn't work because the abstract has no constructor (expected I guess) type AC3 = InstanceType<typeof ACS>["x"] // Type 'typeof ACS' does not satisfy the constraint 'new (...args: any) => any' type AC4 = ConstructorParameters<typeof ACS> // Type 'typeof ACS' does not satisfy the constraint 'new (...args: any) => any'. // but the intersection of the type with anything makes it somehow work... ? // as if the intersection made the class get "unabstracted" type AC1 = InstanceType<(typeof ACS) & {whatever: any}>["x"] // weirdly enough this gives string type AC2 = ConstructorParameters<(typeof ACS) & {whatever: any}> // weirdly enough this gives [number]
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on Oct 21, 2025
TypeScript Version: 3.7.3
Search Terms: abstract class, generic, infer
Code
Expected behavior:
There should be a way to make abstract classes keep the generic information and use it.
Actual behavior:
There's no way to make abstract classes keep the generic information and use it (unless they are type-casted to non abstract classes by adding to them a fake constructor).
Related Issues: #26829