Change Capitalize and Uncapitalize from intrinsic

[sno2]

Suggestion

✅ Viability 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, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

lib Update Request

Configuration Check

My compilation target is ES2015 and my lib is the default.

Sample Code

Inside of lib.es5.d.ts, the Capitalize and Uncapitalize types are typed as intrinsic. However, these can easily be created in regular TS with the following:

type Capitalize<S extends string> = S extends `${infer C}${infer $S}` ? `${Uppercase<C>}${$S}` : never;

type Uncapitalize<S extends string> = S extends `${infer C}${infer $S}` ? `${Lowercase<C>}${$S}` : never;

[sno2]

#41283 is related.

[sno2]

I don't agree with this idea anymore because TypeScript overflows with a way too little amount of characters using this method.