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Rollup merge of rust-lang#74698 - ayrtonm:handle-traitref-mismatch, r…
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…=estebank

fixed error reporting for mismatched traits

mismatched traits were previously referred to as types

closes rust-lang#72217
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Dylan-DPC authored Jul 24, 2020
2 parents 7d545ed + b75ed4f commit a64b544
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Showing 3 changed files with 54 additions and 5 deletions.
29 changes: 24 additions & 5 deletions src/librustc_infer/infer/error_reporting/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1402,8 +1402,12 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}

debug!("note_type_err(diag={:?})", diag);
enum Mismatch<'a> {
Variable(ty::error::ExpectedFound<Ty<'a>>),
Fixed(&'static str),
}
let (expected_found, exp_found, is_simple_error) = match values {
None => (None, None, false),
None => (None, Mismatch::Fixed("type"), false),
Some(values) => {
let (is_simple_error, exp_found) = match values {
ValuePairs::Types(exp_found) => {
Expand All @@ -1417,9 +1421,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
)
.report(diag);

(is_simple_err, Some(exp_found))
(is_simple_err, Mismatch::Variable(exp_found))
}
_ => (false, None),
ValuePairs::TraitRefs(_) => (false, Mismatch::Fixed("trait")),
_ => (false, Mismatch::Fixed("type")),
};
let vals = match self.values_str(&values) {
Some((expected, found)) => Some((expected, found)),
Expand All @@ -1445,8 +1450,18 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
};
if let Some((expected, found)) = expected_found {
let expected_label = exp_found.map_or("type".into(), |ef| ef.expected.prefix_string());
let found_label = exp_found.map_or("type".into(), |ef| ef.found.prefix_string());
let expected_label = match exp_found {
Mismatch::Variable(ef) => ef.expected.prefix_string(),
Mismatch::Fixed(s) => s.into(),
};
let found_label = match exp_found {
Mismatch::Variable(ef) => ef.found.prefix_string(),
Mismatch::Fixed(s) => s.into(),
};
let exp_found = match exp_found {
Mismatch::Variable(exp_found) => Some(exp_found),
Mismatch::Fixed(_) => None,
};
match (&terr, expected == found) {
(TypeError::Sorts(values), extra) => {
let sort_string = |ty: Ty<'tcx>| match (extra, &ty.kind) {
Expand Down Expand Up @@ -1499,6 +1514,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
}
}
let exp_found = match exp_found {
Mismatch::Variable(exp_found) => Some(exp_found),
Mismatch::Fixed(_) => None,
};
if let Some(exp_found) = exp_found {
self.suggest_as_ref_where_appropriate(span, &exp_found, diag);
}
Expand Down
12 changes: 12 additions & 0 deletions src/test/ui/error-codes/E0308-2.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
trait DynEq {}

impl<'a> PartialEq for &'a (dyn DynEq + 'static) {
fn eq(&self, _other: &Self) -> bool {
true
}
}

impl Eq for &dyn DynEq {} //~ ERROR E0308

fn main() {
}
18 changes: 18 additions & 0 deletions src/test/ui/error-codes/E0308-2.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
error[E0308]: mismatched types
--> $DIR/E0308-2.rs:9:6
|
LL | impl Eq for &dyn DynEq {}
| ^^ lifetime mismatch
|
= note: expected trait `std::cmp::PartialEq`
found trait `std::cmp::PartialEq`
note: the lifetime `'_` as defined on the impl at 9:13...
--> $DIR/E0308-2.rs:9:13
|
LL | impl Eq for &dyn DynEq {}
| ^
= note: ...does not necessarily outlive the static lifetime

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.

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