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Generic Constraints working incorrectly #29000
Description
TypeScript Version: 3.2.2
Code
type Omit<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>;
interface IName {
name: string;
}
const callWithName =
<T extends IName, R>(fn: (origianlArgs: T) => R, name: string) =>
(arg: Omit<T, 'name'>) =>
fn({
...arg,
name,
});
const greeting = (arg: { name: string }) => {
console.log(`Hello ${arg.name}`);
}
const greetingToTom = callWithName(greeting, 'Tom');
greetingToTom({});Expected behavior:
shouldn't have any type error
Actual behavior:
has a error:
Argument of type '{ name: string; }' is not assignable to parameter of type 'T'.
Playground Link:
Related Issues:
Activity
jack-williams commentedon Dec 13, 2018
EDIT: Outdated comment. I wont delete the comment so you can read the history if you want.
jack-williams commentedon Dec 13, 2018
No problem. If I were you I would edit your initial post with the new example (and I'll probably remove / edit my comment too).
This looks familiar to other posts I've seen but I can't say if this is a duplicate. Your
nameparameter should be something likeT["name"]though, as it might be the case thatTis instantiated with something more precise thanstring, like"foobar".This seems to boil down to whether
{ name: T["name"]; } & Pick<T, Exclude<keyof T, "name">>should be assignable toT.Sorry I can't be more help!
hronro commentedon Dec 13, 2018
Jack Williams (@jack-williams) Thanks. And I found a issue here which is similar: #28748
So maybe my issue is duplicated?
jack-williams commentedon Dec 13, 2018
Possibly; this issue also looks similar #28821. I don't know enough to say if this is a duplicate so I would wait for someone more knowledgeable to drop by.
DanielRosenwasser commentedon Dec 13, 2018
Potentially a dupe; I'll let Anders Hejlsberg (@ahejlsberg) decide.
sveyret commentedon Dec 15, 2018
Also similar to #28884.
ahejlsberg commentedon Dec 17, 2018
Duplicate of #28884.
typescript-bot commentedon Dec 20, 2018
This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.