Repository navigation
Generic inference from LHS of assignment when destructuring can lead to unexpected anys #45074
Description
Bug Report
🔎 Search Terms
Generic inference, destructuring, binding patterns
🕗 Version & Regression Information
Exists in 4.3.5
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about generics
⏯ Playground Link
Playground link with relevant code
💻 Code
declare function genericFunc<T>(): T;
const { bar } = genericFunc();
// `bar` is `any` here.🙁 Actual behavior
bar is any and T is inferred to be { bar: any }.
🙂 Expected behavior
The inferred type of T should be unknown and there should be an error from trying to destructure it.
(Or, T could still be inferred as { bar: any } but then noImplicitAny should trigger an error. This seems at a glance less desirable to me than the former, but I don't know enough how generic inference works to make a more informed recommendation. Anyways, some sort of error no matter how it happens is what would be ideal!)
Notes: see #43371 (comment) for the original context.
Activity
andrewbranch commentedon Jul 21, 2021
The inference of
{ bar: any }may or may not be avoidable without breaking a lot of other inferences, but it should at least error undernoImplicitAny.andrewbranch commentedon Jul 21, 2021
Related: #43605
jkillian commentedon Oct 1, 2021
Related to the discussion in #46012 I believe
andrewbranch commentedon Oct 4, 2021
Yeah. Probably not going to fix the
noImplicitAnyerror for 4.5 because I want to investigate making this whole pattern an error in the 4.6 timeframe, as discussed in that design meeting.jkillian commentedon May 24, 2022
Love that this is fixed, thanks Andrew Branch (@andrewbranch)!