Support safe index access for noImplicitAny

It is hard to use noImplicitAny without enabling suppressImplicitAnyIndexErrors on the current TypeScript.

Search Terms

noImplicitAny suppressImplicitAnyIndexErrors

Suggestion

Provide safe indexes without explicit type declarations to avoid unsafe index access errors.

Use Cases

• for-in
• Object.keys

Examples

const o = {};
for (const key in o) {
    o[key]; // Should be no error.
}
for (const key of Object.keys(o)) {
    o[key]; // Should be no error.
}

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code (for-in only)
• 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.

Comienza revisando el comportamiento de noImplicitAny y suppressImplicitAnyIndexErrors descrito en el issue, junto con los ejemplos de for-in y Object.keys. Se considera terminado cuando los accesos indexados mostrados se aceptan de forma segura sin declaraciones de tipo explícitas, manteniendo las restricciones indicadas de tiempo de ejecución y compatibilidad con JavaScript.