Write a function to define types.

Search Terms

type defination, functional type defination, meta, meta programming, dynamic type declaration

Suggestion

Write a function to define types.

Use Cases

Build a more complex type.

Examples

type MyType<T extends string>{
  if(T extends 'a'){
    return 'a' //type 'a'
  }
  if(T extends 'b'){
    return 'b' //type 'b'
  }
  return string
}

Checklist

My suggestion meets these guidelines:

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

El issue no menciona archivos, tests ni puntos de entrada. Lee primero la discusión del issue para aclarar la sintaxis y la semántica de la función propuesta a nivel de tipos; después, identifica el área relevante del compilador y define tests que establezcan el comportamiento esperado.