Cannot use 'this' type in type argument on base types

interface Foo<T> {
    thing: T;
}

interface Bar extends Foo<this> {
    thing: this;
}

class Foo<T> {
    thing: T;
}

class Bar extends Foo<this> {
    thing: this;
}

interface Foo<T> {
    thing: T;
}

class Bar implements Foo<this> {
    thing: this;
}

These examples have an error on the 'this' type argument of Foo:

TS2526  A 'this' type is available only in a non-static member of a class or interface.

Since an object type cannot reference a type parameter directly within a heritage clause, we shouldn't be giving this error.

The class is by design, as the type parameter could be used in the constructor. but the interface seems reasonable.

as the type parameter could be used in the constructor

Can you elaborate what you mean? I'm not necessarily seeing the issue in that case.

Related to #6223. While subtly different, I suspect they are in the same problem space.

Well...we could use it for Mithril.js types, where we were looking to add class support. We could avoid creating an entire boilerplate type by just allowing this as a generic parameter in the implements clause. Just thought I'd bring that up.

(Oh, and this would also help quite a bit from the other end.)

Seems to not be a very popular scenario

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Cannot use 'this' type in type argument on base types #7289

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Cannot use 'this' type in type argument on base types #7289

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mhegazy commented on Apr 26, 2016

DanielRosenwasser commented on Apr 26, 2016

kitsonk commented on May 17, 2016

dead-claudia commented on Feb 14, 2017

RyanCavanaugh commented on Jul 22, 2020

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