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Rollup merge of #136415 - estebank:highlight-clarification, r=compiler-errors

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Highlight clarifying information in "expected/found" error

When the expected and found types have the same textual representation, we add clarifying in parentheses. We now visually highlight it in the output.

Detect a corner case where the clarifying information would be the same for both types and skip it, as it doesn't add anything useful.

![Screenshot of the rustc highlighted output on the terminal](https://github.com/user-attachments/assets/aa4b9433-5332-4941-b2c2-1a43e5cadff7)
This commit is contained in:
Matthias Krüger 2025-02-02 18:05:24 +01:00 • committed by GitHub
commit 7e3d872bc0
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6 changed files with 160 additions and 27 deletions
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20
compiler/rustc_errors/src/diagnostic.rs
View file

@ -644,7 +644,14 @@ 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]
@ -654,8 +661,8 @@ 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() {
@ -680,10 +687,13 @@ 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);

34
compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
View file

@ -1722,32 +1722,42 @@ 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| {
@ -1764,26 +1774,26 @@ 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),
sort_string(values.expected),
sort_string(values.found),
);
}
}
}
}
_ => {
debug!(
"note_type_err: exp_found={:?}, expected={:?} found={:?}",

16
tests/ui/error-emitter/E0308-clarification.rs Normal file
View file

@ -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
tests/ui/error-emitter/E0308-clarification.svg Normal file
View file

@ -0,0 +1,97 @@
<svg width="740px" height="668px" xmlns="http://www.w3.org/2000/svg">
<style>
.fg { fill: #AAAAAA }
.bg { background: #000000 }
.fg-ansi256-009 { fill: #FF5555 }
.fg-ansi256-012 { fill: #5555FF }
.fg-magenta { fill: #AA00AA }
.container {
padding: 0 10px;
line-height: 18px;
}
.bold { font-weight: bold; }
tspan {
font: 14px SFMono-Regular, Consolas, Liberation Mono, Menlo, monospace;
white-space: pre;
line-height: 18px;
}
</style>
<rect width="100%" height="100%" y="0" rx="4.5" class="bg" />
<text xml:space="preserve" class="container fg">
<tspan x="10px" y="28px"><tspan class="fg-ansi256-009 bold">error[E0308]</tspan><tspan class="bold">: mismatched types</tspan>
</tspan>
<tspan x="10px" y="46px"><tspan> </tspan><tspan class="fg-ansi256-012 bold"> ╭▸ </tspan><tspan>$DIR/E0308-clarification.rs:15:10</tspan>
</tspan>
<tspan x="10px" y="64px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan>
</tspan>
<tspan x="10px" y="82px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> fn hide&lt;T: Foo&gt;(x: T) -&gt; impl Foo {</tspan>
</tspan>
<tspan x="10px" y="100px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">┬───────</tspan>
</tspan>
<tspan x="10px" y="118px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan>
</tspan>
<tspan x="10px" y="136px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">the expected opaque type</tspan>
</tspan>
<tspan x="10px" y="154px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">the found opaque type</tspan>
</tspan>
<tspan x="10px" y="172px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">‡</tspan>
</tspan>
<tspan x="10px" y="190px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> x = (x.1, x.0);</tspan>
</tspan>
<tspan x="10px" y="208px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">━━━</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">expected `u32`, found `i32`</tspan>
</tspan>
<tspan x="10px" y="226px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan>
</tspan>
<tspan x="10px" y="244px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">├ </tspan><tspan class="bold">note</tspan><tspan>: expected opaque type `</tspan><tspan class="fg-magenta bold">impl Foo</tspan><tspan>` (</tspan><tspan class="fg-magenta bold">`u32`</tspan><tspan>)</tspan>
</tspan>
<tspan x="10px" y="262px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> found opaque type `</tspan><tspan class="fg-magenta bold">impl Foo</tspan><tspan>` (</tspan><tspan class="fg-magenta bold">`i32`</tspan><tspan>)</tspan>
</tspan>
<tspan x="10px" y="280px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">╰ </tspan><tspan class="bold">note</tspan><tspan>: distinct uses of `impl Trait` result in different opaque types</tspan>
</tspan>
<tspan x="10px" y="298px">
</tspan>
<tspan x="10px" y="316px"><tspan class="fg-ansi256-009 bold">error[E0308]</tspan><tspan class="bold">: mismatched types</tspan>
</tspan>
<tspan x="10px" y="334px"><tspan> </tspan><tspan class="fg-ansi256-012 bold"> ╭▸ </tspan><tspan>$DIR/E0308-clarification.rs:15:15</tspan>
</tspan>
<tspan x="10px" y="352px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan>
</tspan>
<tspan x="10px" y="370px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> fn hide&lt;T: Foo&gt;(x: T) -&gt; impl Foo {</tspan>
</tspan>
<tspan x="10px" y="388px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">┬───────</tspan>
</tspan>
<tspan x="10px" y="406px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan>
</tspan>
<tspan x="10px" y="424px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">the expected opaque type</tspan>
</tspan>
<tspan x="10px" y="442px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">the found opaque type</tspan>
</tspan>
<tspan x="10px" y="460px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">‡</tspan>
</tspan>
<tspan x="10px" y="478px"><tspan class="fg-ansi256-012 bold">LL</tspan><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> x = (x.1, x.0);</tspan>
</tspan>
<tspan x="10px" y="496px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">━━━</tspan><tspan> </tspan><tspan class="fg-ansi256-009 bold">expected `i32`, found `u32`</tspan>
</tspan>
<tspan x="10px" y="514px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan>
</tspan>
<tspan x="10px" y="532px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">├ </tspan><tspan class="bold">note</tspan><tspan>: expected opaque type `</tspan><tspan class="fg-magenta bold">impl Foo</tspan><tspan>` (</tspan><tspan class="fg-magenta bold">`i32`</tspan><tspan>)</tspan>
</tspan>
<tspan x="10px" y="550px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">│</tspan><tspan> found opaque type `</tspan><tspan class="fg-magenta bold">impl Foo</tspan><tspan>` (</tspan><tspan class="fg-magenta bold">`u32`</tspan><tspan>)</tspan>
</tspan>
<tspan x="10px" y="568px"><tspan> </tspan><tspan class="fg-ansi256-012 bold">╰ </tspan><tspan class="bold">note</tspan><tspan>: distinct uses of `impl Trait` result in different opaque types</tspan>
</tspan>
<tspan x="10px" y="586px">
</tspan>
<tspan x="10px" y="604px"><tspan class="fg-ansi256-009 bold">error</tspan><tspan class="bold">: aborting due to 2 previous errors</tspan>
</tspan>
<tspan x="10px" y="622px">
</tspan>
<tspan x="10px" y="640px"><tspan class="bold">For more information about this error, try `rustc --explain E0308`.</tspan>
</tspan>
<tspan x="10px" y="658px">
</tspan>
</text>
</svg>
Side by side

After

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4
tests/ui/impl-trait/impl-trait-in-macro.stderr
View file

@ -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

4
tests/ui/impl-trait/universal-two-impl-traits.stderr
View file

@ -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