[Feature request] keyword `final` type for output full final type in .d.ts

[bluelovers]

Search Terms

Suggestion

with keyword final, output a final type typescript know in .d.ts

Use Cases

this help when we import a.ts will didn't need import other file for get type info

Examples

b.ts

export type A2 = {
	a: number,
}

export type B2 = {
	b: number,
}

origin

a.ts

import { A2, B2 } from './b'

type A1 = {
	a: number,
}

type B1 = {
	b: number,
}

export type C1 = A1 & B1
export type C2 = A2 & B2

=>

.d.ts

import { A2, B2 } from './b';
declare type A1 = {
    a: number;
};
declare type B1 = {
    b: number;
};
export declare type C1 = A1 & B1;
export declare type C2 = A2 & B2;

with keyword final

a.ts

import { A2, B2 } from './b'

export type A1 = {
	a: number,
}

export type B1 = {
	b: number,
}

export final type C1 = A1 & B1
export final type C2 = A2 & B2

=>

will no need to know what is A1 B1

and also will not import b.ts for know what is A2, B2 when import a.ts

export declare type C1 = {
	a: number,
	b: number,
}
export declare type C2 = {
	a: number,
	b: number,
}

or

export declare type C1 = {
	a: number,
} & {
	b: number,
}
export declare type C2 = {
	a: number,
} & {
	b: number,
}

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.