Mapped Type bug with modifiers

[marcomura]

Putting parenthesis around the "keyof T" syntax in an inline Mapped Type, strips out the field modifier (readonly).
Without parenthesis, or defining a template using the parenthesis, this doesn't happen.

TypeScript Version: 2.1.1

Code

interface MyType {
  readonly a: number;
  b: string;
}

type MyType2 = {
  [P in keyof MyType]: MyType[P];
}

type MyType3 = {
  [P in (keyof MyType)]: MyType[P];
}

type Test<T> = {
  [P in (keyof T)]: T[P];
}
type MyType4 = Test<MyType>;

Expected behavior:
MyType2, MyType3, and MyType4 to all have the same signature.

Actual behavior:
MyType2 and MyType4 keeps the original MyType signature with modifiers.
MyType3 strips out the modifiers:

{
  a: number;
  b: string;
}

[mhegazy]

This should be fixed in TS 2.1.5

[nitzantomer]

May I ask what exactly is the bug?
Is it supposed to work like it does with the parenthesis or without?

If it should keep the readonly modifiers, how can you create a writeable version of a readonly type?

[marcomura]

I guess it's supposed to work like it does without parenthesis, but I was more looking for consistency here.
Anyway, I agree that right now we lack the possibility of removing the readonly, even if mhegazy explained a workaround here:
https://github.com/Microsoft/TypeScript/issues/13723

Unfortunately, that workaround also removes the optional attribute, and it can't be declared to work recursively :(

[yortus]

Bump. I just ran into this. Will this bug be getting a milestone?

[mhegazy]

this is working as intended, it was meant as a way to allow for removal of readonly modifier.

[typescript-bot]

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