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
Download patch file Download diff file Expand all files Collapse all files

18
compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
View file

@ -573,7 +573,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
if !is_trait_sig {
err.span_suggestion_verbose(
err_help_span,
&format!(
format!(
"consider changing this to be a mutable {pointer_desc}"
),
suggested_code,
@ -582,7 +582,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
} else if let Some(x) = local_trait {
err.span_suggestion_verbose(
x,
&format!(
format!(
"consider changing that to be a mutable {pointer_desc}"
),
suggested_code,
@ -636,14 +636,14 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
};
err.span_suggestion_verbose(
span,
&format!("consider {changing} this binding's type"),
format!("consider {changing} this binding's type"),
sugg,
Applicability::HasPlaceholders,
);
} else {
err.span_label(
err_label_span,
&format!(
format!(
"consider changing this binding's type to be: `{message}`"
),
);
@ -679,13 +679,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
match opt_source {
Some(BorrowedContentSource::OverloadedDeref(ty)) => {
err.help(&format!(
err.help(format!(
"trait `DerefMut` is required to modify through a dereference, \
but it is not implemented for `{ty}`",
));
}
Some(BorrowedContentSource::OverloadedIndex(ty)) => {
err.help(&format!(
err.help(format!(
"trait `IndexMut` is required to modify indexed content, \
but it is not implemented for `{ty}`",
));
@ -736,7 +736,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
// val[index] = rv;
// ---------- place
self.err.multipart_suggestions(
&format!(
format!(
"to modify a `{}`, use `.get_mut()`, `.insert()` or the entry API",
self.ty,
),
@ -788,7 +788,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
{
// val[index].path(args..);
self.err.multipart_suggestion(
&format!("to modify a `{}` use `.get_mut()`", self.ty),
format!("to modify a `{}` use `.get_mut()`", self.ty),
vec![
(
val.span.shrink_to_hi().with_hi(index.span.lo()),
@ -822,7 +822,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
let mut v = V { assign_span, err, ty, suggested: false };
v.visit_body(body);
if !v.suggested {
err.help(&format!(
err.help(format!(
"to modify a `{ty}`, use `.get_mut()`, `.insert()` or the entry API",
));
}