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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

6
compiler/rustc_parse/src/lib.rs
View File

@@ -153,7 +153,7 @@ fn try_file_to_source_file(
) -> Result<Lrc<SourceFile>, Diagnostic> {
sess.source_map().load_file(path).map_err(|e| {
let msg = format!("couldn't read {}: {}", path.display(), e);
let mut diag = Diagnostic::new(Level::Fatal, &msg);
let mut diag = Diagnostic::new(Level::Fatal, msg);
if let Some(sp) = spanopt {
diag.set_span(sp);
}
@@ -190,7 +190,7 @@ pub fn maybe_file_to_stream(
override_span: Option<Span>,
) -> Result<TokenStream, Vec<Diagnostic>> {
let src = source_file.src.as_ref().unwrap_or_else(|| {
sess.span_diagnostic.bug(&format!(
sess.span_diagnostic.bug(format!(
"cannot lex `source_file` without source: {}",
sess.source_map().filename_for_diagnostics(&source_file.name)
));
@@ -247,7 +247,7 @@ pub fn parse_cfg_attr(
match parse_in(parse_sess, tokens.clone(), "`cfg_attr` input", |p| p.parse_cfg_attr()) {
Ok(r) => return Some(r),
Err(mut e) => {
e.help(&format!("the valid syntax is `{}`", CFG_ATTR_GRAMMAR_HELP))
e.help(format!("the valid syntax is `{}`", CFG_ATTR_GRAMMAR_HELP))
.note(CFG_ATTR_NOTE_REF)
.emit();
}