typeof with extended generic class

[rzcoder]

TypeScript Version: 2.4.0+

Code

interface AP {
    id: string;
}

class A<T extends AP = AP> {
    foo(a: T) { }
}

interface BP extends AP {
    n: number;
}

class B<T extends BP = BP> extends A<T> {
}

let y: typeof A;
y = B; // <<<

Expected behavior:
No errors.

Actual behavior:
Error in ts 2.4+ (in 2.3.4 no errors)

Type 'typeof B' is not assignable to type 'typeof A'.
  Type 'B<BP>' is not assignable to type 'A<T>'.
    Types of property 'foo' are incompatible.
      Type '(a: BP) => void' is not assignable to type '(a: T) => void'.
        Types of parameters 'a' and 'a' are incompatible.
          Type 'T' is not assignable to type 'BP'.
            Type 'AP' is not assignable to type 'BP'.
              Property 'n' is missing in type 'AP'.

[mhegazy]

looks like the same issue as #18387. please see #18387 (comment)

[rzcoder]

@mhegazy so, you mean this behaviour is correct?

[mhegazy]

@mhegazy so, you mean this behavior is correct?

yes. it is unsafe to substitute a generic constructor with one that is not generic in the general case. you can either change your base class, to be non-generic, or use --noStrictGenerics to suppress the error.

[rzcoder]

So, in this case you just can't extend React component in that simple way. Pretty common scenario but failed in ts, ok :(

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.