bjoernager/rust
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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
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4
compiler/rustc_mir_transform/src/elaborate_drops.rs
View file

@ -366,7 +366,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
if maybe_dead {
self.tcx.sess.delay_span_bug(
terminator.source_info.span,
&format!(
format!(
"drop of untracked, uninitialized value {:?}, place {:?} ({:?})",
bb, place, path
),
@ -440,7 +440,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
) {
self.tcx.sess.delay_span_bug(
terminator.source_info.span,
&format!("drop of untracked value {:?}", bb),
format!("drop of untracked value {:?}", bb),
);
}
// A drop and replace behind a pointer/array/whatever.

5
compiler/rustc_mir_transform/src/generator.rs
View file

@ -865,7 +865,7 @@ fn sanitize_witness<'tcx>(
_ => {
tcx.sess.delay_span_bug(
body.span,
&format!("unexpected generator witness type {:?}", witness.kind()),
format!("unexpected generator witness type {:?}", witness.kind()),
);
return;
}
@ -1451,8 +1451,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
)
}
_ => {
tcx.sess
.delay_span_bug(body.span, &format!("unexpected generator type {}", gen_ty));
tcx.sess.delay_span_bug(body.span, format!("unexpected generator type {}", gen_ty));
return;
}
};