No excess property error for computed property

TypeScript Version: 3.7.5 and 3.9.0-dev.20200220

Search Terms: excess property, computed property, index signature

Code

interface Foo {
	a: string;
} 

const bar: Foo = {
	a: "",
	z: "" // error, excess prop
}

const baz: Foo = {
	a: "",
	["Z".toLowerCase()]: "" // this is okay I guess?
}

Expected behavior:
The computed property in the definition of baz should maybe produce an excess property error, since Foo has no string index signature and "Z".toLowerCase() is only known to be a string.

Actual behavior:
The computed property is allowed.

Playground Link: Here

Related Issues: #22427

This issue is a re-opening of #22427, which was marked as a bug and closed as "fixed", but I don't see an actual fix referenced anywhere in that issue and the behavior described in that issue persists. Any ideas? Thanks!

There's an SO question asking this, which brought me to #22427, which has me scratching my head 😕.

Comienza con la reproducción en TypeScript Playground del issue y compara el caso de la propiedad calculada con el caso directo de propiedades en exceso. Lee el issue relacionado #22427 para entender la discusión anterior; se considera terminado cuando el comportamiento esperado de las propiedades en exceso se haya resuelto o el comportamiento previsto esté documentado mediante pruebas actualizadas del compilador.