From #15102 (comment)

This is still showing errors if the class and its use are in separate files.

a.ts

let foo: typeof C;

b.ts

class C {}

tsconfig.json

{
  "compilerOptions": {
      "outFile": "foo"
  }
}

Shows: src/a.ts(1,17): error TS2449: Class 'C' used before its declaration.