Confusing error when trying to call non-function

[emberian]

render/man.rs:62:28: 62:43 error: expected function but found `&'static str`
render/man.rs:62                     let s = shortty(&item);
                                             ^~~~~~~~~~~~~~~

It should say something like

error: cannot call non-callable `shortty`; expected function but found `T`
...
note: `shortty` declared here

The big thing is the pointer to the thing it thinks you're trying to call!

[flaper87]

Triage: Still valid. Here's a test case for this bug:

fn main() {
    let shortty = "test";
    shortty();
}

I agree a note would be very useful for this and similar cases.

[frewsxcv]

Triage: The output hasn't changed much since when this was first reported.

/tmp $ echo 'fn main() { let shortty = "test"; shortty(); }' > hello.rs
/tmp $ rustc hello.rs
hello.rs:1:35: 1:44 error: expected function, found `&str`
hello.rs:1 fn main() { let shortty = "test"; shortty(); }
                                             ^~~~~~~~~
error: aborting due to previous error

Personally, I don't think this error message is that confusing.

The big thing is the pointer to the thing it thinks you're trying to call!

@cmr What do you mean by this?

[jdm]

@frewsxcv @cmr means the extra note he suggested in the original report: note: foo declared here.

[Manishearth]

Willing to mentor this.

Relevant code: https://github.com/rust-lang/rust/blob/master/src/librustc_typeck/check/callee.rs#L231

You need to find the defid of the call expression (use def_map in fcx.tcx()), and do something similar as done here to point out where something was imported or defined. It might be useful to refactor that out in a note_did_import utility function that takes two strings and a def id or something and reports on the import or definition, whichever is local.

[Detegr]

This looks like a bug I could be able to fix, so I'll try getting something done this weekend.

[Manishearth]

Sure!

[Manishearth]

@Detegr Btw, http://manishearth.github.io/rust-internals-docs/rustc/ is a searchable set of online docs for the internals.

http://manishearth.github.io/rust-internals-docs/rustc/middle/ty/struct.ctxt.html , specifically the DefMap is what you need here.

[Manishearth]

@Detegr ignore the advice about refactoring it. We should just note that it is a local variable if it is indeed local. I don't think there's an easy way of figuring out where something was imported from.

[Detegr]

@Manishearth All right. If there is no need for refactoring, I think I have it working correctly now. I'll do a PR later today. Thanks for all the tips, they helped a lot.