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Auto merge of #111748 - nnethercote:Cow-DiagnosticMessage, r=WaffleLapkin

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Use `Cow` in `{D,Subd}iagnosticMessage`.

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.

r? `@WaffleLapkin`
This commit is contained in:
bors 2023-05-29 07:10:44 +00:00
commit 70e04bd88d
45 changed files with 308 additions and 287 deletions
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2
compiler/rustc_builtin_macros/src/compile_error.rs
View file

@ -18,7 +18,7 @@ pub fn expand_compile_error<'cx>(
reason = "diagnostic message is specified by user"
)]
#[expect(rustc::untranslatable_diagnostic, reason = "diagnostic message is specified by user")]
cx.span_err(sp, var.as_str());
cx.span_err(sp, var.to_string());
DummyResult::any(sp)
}

2
compiler/rustc_builtin_macros/src/errors.rs
View file

@ -377,7 +377,7 @@ impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for EnvNotDefined {
rustc::untranslatable_diagnostic,
reason = "cannot translate user-provided messages"
)]
handler.struct_diagnostic(msg.as_str())
handler.struct_diagnostic(msg.to_string())
} else {
handler.struct_diagnostic(crate::fluent_generated::builtin_macros_env_not_defined)
};