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Improve error message for using value as type #29778
Description
TypeScript Version: 3.4.0-dev.20190206
Search Terms: "cannot find name" type error
Code
If you use a type as a value you get a nice error message:
type t = number;
let x = t;
// error TS2693: 't' only refers to a type, but is being used as a value here.But if you do the same thing in reverse, you get a really confusing one:
let t = 3;
let x: t;
// error TS2304: Cannot find name 't'.Expected behavior:
Error message should say something more like the type one.
Actual behavior:
Error message suggests there is no 't' in scope at all, which is very confusing especially when you have imported t from some other file and you thought it was a type.
Playground Link:
Related Issues:
There are some around this same problem with namespaces I think, like
#26391 or #12075
I think this issue is more broadly complaining about issues in this area:
#27630
But the issue I'm filing here is very specific and concrete, with an easy repro.
This issue discusses some suggested fixes for this issue, but I think first we need to fix the error message.
#28975
Activity
DanielRosenwasser commentedon Feb 6, 2019
Duplicate of #28975?
evmar commentedon Feb 6, 2019
Hm, that one is really close. But it is saying we should suggest a specific fix, and is bogged down in how it's hard to pick the right fix. Here I'm asking to at least fix the error message (without necessarily suggesting a fix), so #28975 I guess would be follow-on work from that.
Edit: I stuck a link to it in the related list.
DanielRosenwasser commentedon Feb 6, 2019
Seems small enough to avoid the bikeshed 🚲🏠.
dragomirtitian commentedon Feb 7, 2019
Daniel Rosenwasser (@DanielRosenwasser) Would the message
't' refers to a value, but is being used as a type here.be too similar to the reverse message ? ('t' only refers to a type, but is being used as a value here.)Also where would be a good place to place the tests for such a feature ?
Merge pull request #29896 from dragomirtitian/GH-29778
DanielRosenwasser commentedon Feb 14, 2019
Thanks for the PR Titian Cernicova-Dragomir (@dragomirtitian)!