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Highlight clarifying information in "expected/found" error #136415

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merged 1 commit into from
Feb 2, 2025
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Highlight clarifying information in "expected/found" error #136415

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20 changes: 15 additions & 5 deletions compiler/rustc_errors/src/diagnostic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -641,7 +641,14 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
found_label: &dyn fmt::Display,
found: DiagStyledString,
) -> &mut Self {
self.note_expected_found_extra(expected_label, expected, found_label, found, &"", &"")
self.note_expected_found_extra(
expected_label,
expected,
found_label,
found,
DiagStyledString::normal(""),
DiagStyledString::normal(""),
)
}

#[rustc_lint_diagnostics]
Expand All @@ -651,8 +658,8 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
expected: DiagStyledString,
found_label: &dyn fmt::Display,
found: DiagStyledString,
expected_extra: &dyn fmt::Display,
found_extra: &dyn fmt::Display,
expected_extra: DiagStyledString,
found_extra: DiagStyledString,
) -> &mut Self {
let expected_label = expected_label.to_string();
let expected_label = if expected_label.is_empty() {
Expand All @@ -677,10 +684,13 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
expected_label
))];
msg.extend(expected.0);
msg.push(StringPart::normal(format!("`{expected_extra}\n")));
msg.push(StringPart::normal(format!("`")));
msg.extend(expected_extra.0);
msg.push(StringPart::normal(format!("\n")));
msg.push(StringPart::normal(format!("{}{} `", " ".repeat(found_padding), found_label)));
msg.extend(found.0);
msg.push(StringPart::normal(format!("`{found_extra}")));
msg.push(StringPart::normal(format!("`")));
msg.extend(found_extra.0);

// For now, just attach these as notes.
self.highlighted_note(msg);
Expand Down
46 changes: 28 additions & 18 deletions compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
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Expand Up @@ -1725,32 +1725,42 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
}
}
TypeError::Sorts(values) => {
let extra = expected == found;
let extra = expected == found
// Ensure that we don't ever say something like
// expected `impl Trait` (opaque type `impl Trait`)
// found `impl Trait` (opaque type `impl Trait`)
&& values.expected.sort_string(self.tcx)
!= values.found.sort_string(self.tcx);
let sort_string = |ty: Ty<'tcx>| match (extra, ty.kind()) {
(true, ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })) => {
let sm = self.tcx.sess.source_map();
let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
format!(
DiagStyledString::normal(format!(
" (opaque type at <{}:{}:{}>)",
sm.filename_for_diagnostics(&pos.file.name),
pos.line,
pos.col.to_usize() + 1,
)
))
}
(true, ty::Alias(ty::Projection, proj))
if self.tcx.is_impl_trait_in_trait(proj.def_id) =>
{
let sm = self.tcx.sess.source_map();
let pos = sm.lookup_char_pos(self.tcx.def_span(proj.def_id).lo());
format!(
DiagStyledString::normal(format!(
" (trait associated opaque type at <{}:{}:{}>)",
sm.filename_for_diagnostics(&pos.file.name),
pos.line,
pos.col.to_usize() + 1,
)
))
}
(true, _) => format!(" ({})", ty.sort_string(self.tcx)),
(false, _) => "".to_string(),
(true, _) => {
let mut s = DiagStyledString::normal(" (");
s.push_highlighted(ty.sort_string(self.tcx));
s.push_normal(")");
s
}
(false, _) => DiagStyledString::normal(""),
};
if !(values.expected.is_simple_text() && values.found.is_simple_text())
|| (exp_found.is_some_and(|ef| {
Expand All @@ -1767,23 +1777,23 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
}
}))
{
if let Some(ExpectedFound { found: found_ty, .. }) = exp_found {
if let Some(ExpectedFound { found: found_ty, .. }) = exp_found
&& !self.tcx.ty_is_opaque_future(found_ty)
{
// `Future` is a special opaque type that the compiler
// will try to hide in some case such as `async fn`, so
// to make an error more use friendly we will
// avoid to suggest a mismatch type with a
// type that the user usually are not using
// directly such as `impl Future<Output = u8>`.
if !self.tcx.ty_is_opaque_future(found_ty) {
diag.note_expected_found_extra(
&expected_label,
expected,
&found_label,
found,
&sort_string(values.expected),
&sort_string(values.found),
);
}
diag.note_expected_found_extra(
&expected_label,
expected,
&found_label,
found,
sort_string(values.expected),
sort_string(values.found),
);
}
}
}
Expand Down
16 changes: 16 additions & 0 deletions tests/ui/error-emitter/E0308-clarification.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
//@ compile-flags: -Zunstable-options --error-format=human-unicode --color=always
//@ only-linux
// Ensure that when we have a type error where both types have the same textual representation, the
// diagnostic machinery highlights the clarifying comment that comes after in parentheses.
trait Foo: Copy + ToString {}

impl<T: Copy + ToString> Foo for T {}

fn hide<T: Foo>(x: T) -> impl Foo {
x
}

fn main() {
let mut x = (hide(0_u32), hide(0_i32));
x = (x.1, x.0);
}
97 changes: 97 additions & 0 deletions tests/ui/error-emitter/E0308-clarification.svg
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4 changes: 2 additions & 2 deletions tests/ui/impl-trait/impl-trait-in-macro.stderr
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Expand Up @@ -12,8 +12,8 @@ LL | let mut a = x;
LL | a = y;
| ^ expected type parameter `impl Debug`, found a different type parameter `impl Debug`
|
= note: expected type parameter `impl Debug` (type parameter `impl Debug`)
found type parameter `impl Debug` (type parameter `impl Debug`)
= note: expected type parameter `impl Debug`
found type parameter `impl Debug`
= note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
= note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters

Expand Down
4 changes: 2 additions & 2 deletions tests/ui/impl-trait/universal-two-impl-traits.stderr
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Expand Up @@ -10,8 +10,8 @@ LL | let mut a = x;
LL | a = y;
| ^ expected type parameter `impl Debug`, found a different type parameter `impl Debug`
|
= note: expected type parameter `impl Debug` (type parameter `impl Debug`)
found type parameter `impl Debug` (type parameter `impl Debug`)
= note: expected type parameter `impl Debug`
found type parameter `impl Debug`
= note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
= note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters

Expand Down
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