bjoernager/rust
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Use Cow in {D,Subd}iagnosticMessage.

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Each of `{D,Subd}iagnosticMessage::{Str,Eager}` has a comment:
```
// FIXME(davidtwco): can a `Cow<'static, str>` be used here?
```
This commit answers that question in the affirmative. It's not the most
compelling change ever, but it might be worth merging.

This requires changing the `impl<'a> From<&'a str>` impls to `impl
From<&'static str>`, which involves a bunch of knock-on changes that
require/result in call sites being a little more precise about exactly
what kind of string they use to create errors, and not just `&str`. This
will result in fewer unnecessary allocations, though this will not have
any notable perf effects given that these are error paths.

Note that I was lazy within Clippy, using `to_string` in a few places to
preserve the existing string imprecision. I could have used `impl
Into<{D,Subd}iagnosticMessage>` in various places as is done in the
compiler, but that would have required changes to *many* call sites
(mostly changing `&format("...")` to `format!("...")`) which didn't seem
worthwhile.
This commit is contained in:
Nicholas Nethercote 2023-05-04 10:55:21 +10:00
parent 1c53407e8c
commit 781111ef35
45 changed files with 308 additions and 287 deletions
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24
compiler/rustc_errors/src/diagnostic.rs
View file

@ -352,14 +352,9 @@ impl Diagnostic {
/// Labels all the given spans with the provided label.
/// See [`Self::span_label()`] for more information.
pub fn span_labels(
&mut self,
spans: impl IntoIterator<Item = Span>,
label: impl AsRef<str>,
) -> &mut Self {
let label = label.as_ref();
pub fn span_labels(&mut self, spans: impl IntoIterator<Item = Span>, label: &str) -> &mut Self {
for span in spans {
self.span_label(span, label);
self.span_label(span, label.to_string());
}
self
}
@ -394,17 +389,18 @@ impl Diagnostic {
expected: DiagnosticStyledString,
found: DiagnosticStyledString,
) -> &mut Self {
let mut msg: Vec<_> = vec![("required when trying to coerce from type `", Style::NoStyle)];
let mut msg: Vec<_> =
vec![(Cow::from("required when trying to coerce from type `"), Style::NoStyle)];
msg.extend(expected.0.iter().map(|x| match *x {
StringPart::Normal(ref s) => (s.as_str(), Style::NoStyle),
StringPart::Highlighted(ref s) => (s.as_str(), Style::Highlight),
StringPart::Normal(ref s) => (Cow::from(s.clone()), Style::NoStyle),
StringPart::Highlighted(ref s) => (Cow::from(s.clone()), Style::Highlight),
}));
msg.push(("` to type '", Style::NoStyle));
msg.push((Cow::from("` to type '"), Style::NoStyle));
msg.extend(found.0.iter().map(|x| match *x {
StringPart::Normal(ref s) => (s.as_str(), Style::NoStyle),
StringPart::Highlighted(ref s) => (s.as_str(), Style::Highlight),
StringPart::Normal(ref s) => (Cow::from(s.clone()), Style::NoStyle),
StringPart::Highlighted(ref s) => (Cow::from(s.clone()), Style::Highlight),
}));
msg.push(("`", Style::NoStyle));
msg.push((Cow::from("`"), Style::NoStyle));
// For now, just attach these as notes
self.highlighted_note(msg);