> the moment I use Object.entries ... the key has been widened to string
This is correct behavior though, and what you propose would be wrong. The type isn’t narrowed. Type U satisfies type T when the keys of U are a superset of the keys of T, so long as the keys map to the correct value-types in the intersection of (keyof T) and (keyof U)
This is because the only time extra keys are outlawed is when you instantiate an object of type T and explicitly declare it as a T. I can link if you need but this is an important subtlety which is why Object.entries returns string instead of keyof T, and it’s not borne of MS/TS developer laziness
This is correct behavior though, and what you propose would be wrong. The type isn’t narrowed. Type U satisfies type T when the keys of U are a superset of the keys of T, so long as the keys map to the correct value-types in the intersection of (keyof T) and (keyof U)
This is because the only time extra keys are outlawed is when you instantiate an object of type T and explicitly declare it as a T. I can link if you need but this is an important subtlety which is why Object.entries returns string instead of keyof T, and it’s not borne of MS/TS developer laziness