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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8
compiler/rustc_errors/src/diagnostic_builder.rs
View file

@ -558,7 +558,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
}
// Take the `Diagnostic` by replacing it with a dummy.
let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::Str("".to_string()));
let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::from(""));
let diagnostic = std::mem::replace(&mut *self.inner.diagnostic, dummy);
// Disable the ICE on `Drop`.
@ -627,7 +627,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
pub fn span_labels(
&mut self,
spans: impl IntoIterator<Item = Span>,
label: impl AsRef<str>,
label: &str,
) -> &mut Self);
forward!(pub fn note_expected_found(
@ -781,8 +781,8 @@ impl Drop for DiagnosticBuilderInner<'_> {
if !panicking() {
handler.emit_diagnostic(&mut Diagnostic::new(
Level::Bug,
DiagnosticMessage::Str(
"the following error was constructed but not emitted".to_string(),
DiagnosticMessage::from(
"the following error was constructed but not emitted",
),
));
handler.emit_diagnostic(&mut self.diagnostic);