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_codegen_ssa/src/codegen_attrs.rs
View file

@ -301,7 +301,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
if let Some(val) = attr.value_str() {
if val.as_str().bytes().any(|b| b == 0) {
let msg = format!("illegal null byte in link_section value: `{}`", &val);
tcx.sess.span_err(attr.span, &msg);
tcx.sess.span_err(attr.span, msg);
} else {
codegen_fn_attrs.link_section = Some(val);
}
@ -631,7 +631,7 @@ fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
} else {
let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
tcx.sess
.struct_span_err(attr.span, &msg)
.struct_span_err(attr.span, msg)
.note("the value may not exceed `u16::MAX`")
.emit();
None