bjoernager/rust
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Use Cow in {D,Subd}iagnosticMessage.

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Each of `{D,Subd}iagnosticMessage::{Str,Eager}` has a comment:
```
// FIXME(davidtwco): can a `Cow<'static, str>` be used here?
```
This commit answers that question in the affirmative. It's not the most
compelling change ever, but it might be worth merging.

This requires changing the `impl<'a> From<&'a str>` impls to `impl
From<&'static str>`, which involves a bunch of knock-on changes that
require/result in call sites being a little more precise about exactly
what kind of string they use to create errors, and not just `&str`. This
will result in fewer unnecessary allocations, though this will not have
any notable perf effects given that these are error paths.

Note that I was lazy within Clippy, using `to_string` in a few places to
preserve the existing string imprecision. I could have used `impl
Into<{D,Subd}iagnosticMessage>` in various places as is done in the
compiler, but that would have required changes to *many* call sites
(mostly changing `&format("...")` to `format!("...")`) which didn't seem
worthwhile.
This commit is contained in:
Nicholas Nethercote 2023-05-04 10:55:21 +10:00
parent 1c53407e8c
commit 781111ef35
45 changed files with 308 additions and 287 deletions
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32
compiler/rustc_error_messages/src/lib.rs
View file

@ -263,8 +263,7 @@ type FluentId = Cow<'static, str>;
#[rustc_diagnostic_item = "SubdiagnosticMessage"]
pub enum SubdiagnosticMessage {
/// Non-translatable diagnostic message.
// FIXME(davidtwco): can a `Cow<'static, str>` be used here?
Str(String),
Str(Cow<'static, str>),
/// Translatable message which has already been translated eagerly.
///
/// Some diagnostics have repeated subdiagnostics where the same interpolated variables would
@ -275,8 +274,7 @@ pub enum SubdiagnosticMessage {
/// incorrect diagnostics. Eager translation results in translation for a subdiagnostic
/// happening immediately after the subdiagnostic derive's logic has been run. This variant
/// stores messages which have been translated eagerly.
// FIXME(#100717): can a `Cow<'static, str>` be used here?
Eager(String),
Eager(Cow<'static, str>),
/// Identifier of a Fluent message. Instances of this variant are generated by the
/// `Subdiagnostic` derive.
FluentIdentifier(FluentId),
@ -290,17 +288,17 @@ pub enum SubdiagnosticMessage {
impl From<String> for SubdiagnosticMessage {
fn from(s: String) -> Self {
SubdiagnosticMessage::Str(s)
SubdiagnosticMessage::Str(Cow::Owned(s))
}
}
impl<'a> From<&'a str> for SubdiagnosticMessage {
fn from(s: &'a str) -> Self {
SubdiagnosticMessage::Str(s.to_string())
impl From<&'static str> for SubdiagnosticMessage {
fn from(s: &'static str) -> Self {
SubdiagnosticMessage::Str(Cow::Borrowed(s))
}
}
impl From<Cow<'static, str>> for SubdiagnosticMessage {
fn from(s: Cow<'static, str>) -> Self {
SubdiagnosticMessage::Str(s.to_string())
SubdiagnosticMessage::Str(s)
}
}
@ -312,8 +310,7 @@ impl From<Cow<'static, str>> for SubdiagnosticMessage {
#[rustc_diagnostic_item = "DiagnosticMessage"]
pub enum DiagnosticMessage {
/// Non-translatable diagnostic message.
// FIXME(#100717): can a `Cow<'static, str>` be used here?
Str(String),
Str(Cow<'static, str>),
/// Translatable message which has already been translated eagerly.
///
/// Some diagnostics have repeated subdiagnostics where the same interpolated variables would
@ -324,8 +321,7 @@ pub enum DiagnosticMessage {
/// incorrect diagnostics. Eager translation results in translation for a subdiagnostic
/// happening immediately after the subdiagnostic derive's logic has been run. This variant
/// stores messages which have been translated eagerly.
// FIXME(#100717): can a `Cow<'static, str>` be used here?
Eager(String),
Eager(Cow<'static, str>),
/// Identifier for a Fluent message (with optional attribute) corresponding to the diagnostic
/// message.
///
@ -363,17 +359,17 @@ impl DiagnosticMessage {
impl From<String> for DiagnosticMessage {
fn from(s: String) -> Self {
DiagnosticMessage::Str(s)
DiagnosticMessage::Str(Cow::Owned(s))
}
}
impl<'a> From<&'a str> for DiagnosticMessage {
fn from(s: &'a str) -> Self {
DiagnosticMessage::Str(s.to_string())
impl From<&'static str> for DiagnosticMessage {
fn from(s: &'static str) -> Self {
DiagnosticMessage::Str(Cow::Borrowed(s))
}
}
impl From<Cow<'static, str>> for DiagnosticMessage {
fn from(s: Cow<'static, str>) -> Self {
DiagnosticMessage::Str(s.to_string())
DiagnosticMessage::Str(s)
}
}