Missing error on class extending union of incompatible constructor types

TypeScript Version: 4.2.0-dev.20210105, worked in v3.6.3, regressed in v3.7

Search Terms: is not a constructor function type

Expected behavior:

Error: Type 'typeof Base | typeof Base2' is not a constructor function type.
Or super should not be inferred as any.

Actual behavior:

No error and super: any

Related Issues:

Code

class Base {
    prop = 1;
}

class Base2 {
    other = 1;
}

const base = Boolean() ? Base : Base2;

class Derived extends base { // ExpressionWithTypeArguments is inferred as 'any', expected error "Type 'typeof Base | typeof Base2' is not a constructor function type."
    static fn() {
        super.wargarbl.wat; // super is inferred as 'any'
    }
    fn() {
        super.wargarbl.wat; // super is inferred as 'any'
    }
}

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "ES2017",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

Start with the TypeScript code example and its provided Playground link, comparing the reported behavior between versions 3.6.3, 3.7, and 4.2.0-dev. Reproduce the missing diagnostic for class Derived extends base and verify that the incompatible constructor union is rejected without inferring super as any.