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Restrict From<S> for {D,Subd}iagnosticMessage.

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Currently a `{D,Subd}iagnosticMessage` can be created from any type that
impls `Into<String>`. That includes `&str`, `String`, and `Cow<'static,
str>`, which are reasonable. It also includes `&String`, which is pretty
weird, and results in many places making unnecessary allocations for
patterns like this:
```
self.fatal(&format!(...))
```
This creates a string with `format!`, takes a reference, passes the
reference to `fatal`, which does an `into()`, which clones the
reference, doing a second allocation. Two allocations for a single
string, bleh.

This commit changes the `From` impls so that you can only create a
`{D,Subd}iagnosticMessage` from `&str`, `String`, or `Cow<'static,
str>`. This requires changing all the places that currently create one
from a `&String`. Most of these are of the `&format!(...)` form
described above; each one removes an unnecessary static `&`, plus an
allocation when executed. There are also a few places where the existing
use of `&String` was more reasonable; these now just use `clone()` at
the call site.

As well as making the code nicer and more efficient, this is a step
towards possibly using `Cow<'static, str>` in
`{D,Subd}iagnosticMessage::{Str,Eager}`. That would require changing
the `From<&'a str>` impls to `From<&'static str>`, which is doable, but
I'm not yet sure if it's worthwhile.
This commit is contained in:
Nicholas Nethercote
2023-04-20 13:26:58 +10:00
parent a368898de7
commit 6b62f37402
177 changed files with 791 additions and 787 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
compiler/rustc_hir_analysis/src/coherence/orphan.rs
View File

@@ -372,10 +372,10 @@ fn emit_orphan_check_error<'tcx>(
if is_target_ty {
// Point at `D<A>` in `impl<A, B> for C<B> in D<A>`
err.span_label(self_ty_span, &msg);
err.span_label(self_ty_span, msg);
} else {
// Point at `C<B>` in `impl<A, B> for C<B> in D<A>`
err.span_label(trait_span, &msg);
err.span_label(trait_span, msg);
}
}
err.note("define and implement a trait or new type instead");
@@ -531,15 +531,15 @@ fn lint_auto_trait_impl<'tcx>(
let self_descr = tcx.def_descr(self_type_did);
match arg {
ty::util::NotUniqueParam::DuplicateParam(arg) => {
lint.note(&format!("`{}` is mentioned multiple times", arg));
lint.note(format!("`{}` is mentioned multiple times", arg));
}
ty::util::NotUniqueParam::NotParam(arg) => {
lint.note(&format!("`{}` is not a generic parameter", arg));
lint.note(format!("`{}` is not a generic parameter", arg));
}
}
lint.span_note(
item_span,
&format!(
format!(
"try using the same sequence of generic parameters as the {} definition",
self_descr,
),