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_cranelift/src/driver/aot.rs
View file

@ -69,7 +69,7 @@ impl OngoingCodegen {
let module_codegen_result = match module_codegen_result {
Ok(module_codegen_result) => module_codegen_result,
Err(err) => sess.fatal(&err),
Err(err) => sess.fatal(err),
};
let ModuleCodegenResult { module_regular, module_global_asm, existing_work_product } =
module_codegen_result;
@ -468,7 +468,7 @@ pub(crate) fn run_aot(
let obj = create_compressed_metadata_file(tcx.sess, &metadata, &symbol_name);
if let Err(err) = std::fs::write(&tmp_file, obj) {
tcx.sess.fatal(&format!("error writing metadata object file: {}", err));
tcx.sess.fatal(format!("error writing metadata object file: {}", err));
}
(metadata_cgu_name, tmp_file)