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Rollup merge of #82220 - henryboisdequin:fixes-80853, r=varkor

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fix the false 'defined here' messages

Closes #80853.

Take this code:

```rust
struct S;

fn repro_ref(thing: S) {
    thing();
}
```

Previously, the error message would be this:

```
error[E0618]: expected function, found `S`
 --> src/lib.rs:4:5
  |
3 | fn repro_ref(thing: S) {
  |              ----- `S` defined here
4 |     thing();
  |     ^^^^^--
  |     |
  |     call expression requires function

error: aborting due to previous error
```

This is incorrect as `S` is not defined in the function arguments, `thing` is defined there. With this change, the following is emitted:

```
error[E0618]: expected function, found `S`
  --> $DIR/80853.rs:4:5
   |
LL | fn repro_ref(thing: S) {
   |              ----- is of type `S`
LL |     thing();
   |     ^^^^^--
   |     |
   |     call expression requires function
   |
   = note: local variable `S` is not a function

error: aborting due to previous error
```

As you can see, this error message points out that `thing` is of type `S` and later in a note, that `S` is not a function. This change does seem like a downside for some error messages. Take this example:

```
LL | struct Empty2;
   | -------------- is of type `Empty2`
```

As you can see, the error message shows that the definition of `Empty2` is of type `Empty2`. Although this isn't wrong, it would be more helpful if it would say something like this (which was there previously):

```
LL | struct Empty2;
   | -------------- `Empty2` defined here
```

If there is a better way of doing this, where the `Empty2` example would stay the same as without this change, please inform me.

**Update: This is now fixed**

CC `@camelid`
This commit is contained in:
Dylan DPC 2021-02-25 14:34:00 +01:00 • committed by GitHub
commit 6bf486711b
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11 changed files with 67 additions and 9 deletions
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23
compiler/rustc_typeck/src/check/callee.rs
View file

@ -4,7 +4,7 @@ use crate::type_error_struct;
use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
use rustc_hir as hir;
use rustc_hir::def::Res;
use rustc_hir::def::{Namespace, Res};
use rustc_hir::def_id::{DefId, LOCAL_CRATE};
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_infer::{infer, traits};
@ -374,7 +374,26 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
|p| format!("`{}` defined here returns `{}`", p, callee_ty),
)
}
_ => Some(format!("`{}` defined here", callee_ty)),
_ => {
match def {
// Emit a different diagnostic for local variables, as they are not
// type definitions themselves, but rather variables *of* that type.
Res::Local(hir_id) => Some(format!(
"`{}` has type `{}`",
self.tcx.hir().name(hir_id),
callee_ty
)),
Res::Def(kind, def_id)
if kind.ns() == Some(Namespace::ValueNS) =>
{
Some(format!(
"`{}` defined here",
self.tcx.def_path_str(def_id),
))
}
_ => Some(format!("`{}` defined here", callee_ty)),
}
}
};
if let Some(label) = label {
err.span_label(span, label);