Assigning compatible concrete class to generic base class typed variable errors out during compile time.

[AfflatusX]

abstract class Base<T> {
  abstract doSomething(val: T): void;
}

class A extends Base<i32> {
  doSomething(val: i32): void {

  }
}

let refA: Base<i32> | null = new A(); 

Repro: https://webassembly.studio/?f=bk298o1egu7

would throw Task build failed: type argument count mismatch

Known problem? Any way to work around it?

[AfflatusX]

Looks like changing A to A passes compilation... Is it just making sure the number of type args needs to match? or there are some more reasoning behind that?

[dcodeIO]

Whenever an assertion is hit or an exception thrown where there should be a diagnostic instead, it's most likely a bug. Something around here it seems.

[AfflatusX]

Yup - I'm poking around that section of code as you commented lol However, I don't have much context on why that check exists in first place (line 4219).

[dcodeIO]

When a concrete Class is instantiated, for example an A<i32> from a ClassPrototype A<T>, it fills in the concrete type parameters. For that it checks that both the number of abstract parameters and concrete arguments matches, which seems to fail, hmm.

[AfflatusX]

Looks like the statement failed was actually the first part: if (!typeParameters .... Indeed in my example A doesn't have type params, but that's expected right?