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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8
compiler/rustc_codegen_cranelift/src/constant.rs
View file

@ -308,7 +308,7 @@ fn data_id_for_static(
attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL),
) {
Ok(data_id) => data_id,
Err(ModuleError::IncompatibleDeclaration(_)) => tcx.sess.fatal(&format!(
Err(ModuleError::IncompatibleDeclaration(_)) => tcx.sess.fatal(format!(
"attempt to declare `{symbol_name}` as static, but it was already declared as function"
)),
Err(err) => Err::<_, _>(err).unwrap(),
@ -356,7 +356,7 @@ fn data_id_for_static(
attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL),
) {
Ok(data_id) => data_id,
Err(ModuleError::IncompatibleDeclaration(_)) => tcx.sess.fatal(&format!(
Err(ModuleError::IncompatibleDeclaration(_)) => tcx.sess.fatal(format!(
"attempt to declare `{symbol_name}` as static, but it was already declared as function"
)),
Err(err) => Err::<_, _>(err).unwrap(),
@ -404,7 +404,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
if let Some(names) = section_name.split_once(',') {
names
} else {
tcx.sess.fatal(&format!(
tcx.sess.fatal(format!(
"#[link_section = \"{}\"] is not valid for macos target: must be segment and section separated by comma",
section_name
));
@ -449,7 +449,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
GlobalAlloc::Static(def_id) => {
if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
{
tcx.sess.fatal(&format!(
tcx.sess.fatal(format!(
"Allocation {:?} contains reference to TLS value {:?}",
alloc_id, def_id
));