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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
Download patch file Download diff file Expand all files Collapse all files

7
compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
View file

@ -25,6 +25,7 @@ use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
use rustc_trait_selection::traits::{
self, ObligationCause, ObligationCauseCode, ObligationCtxt, Reveal,
};
use std::borrow::Cow;
use std::iter;
/// Checks that a method from an impl conforms to the signature of
@ -684,7 +685,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
&cause,
hir.get_if_local(impl_m.def_id)
.and_then(|node| node.fn_decl())
.map(|decl| (decl.output.span(), "return type in trait".to_owned())),
.map(|decl| (decl.output.span(), Cow::from("return type in trait"))),
Some(infer::ValuePairs::Terms(ExpectedFound {
expected: trait_return_ty.into(),
found: impl_return_ty.into(),
@ -963,7 +964,7 @@ fn report_trait_method_mismatch<'tcx>(
infcx.err_ctxt().note_type_err(
&mut diag,
&cause,
trait_err_span.map(|sp| (sp, "type in trait".to_owned())),
trait_err_span.map(|sp| (sp, Cow::from("type in trait"))),
Some(infer::ValuePairs::Sigs(ExpectedFound { expected: trait_sig, found: impl_sig })),
terr,
false,
@ -1731,7 +1732,7 @@ pub(super) fn compare_impl_const_raw(
infcx.err_ctxt().note_type_err(
&mut diag,
&cause,
trait_c_span.map(|span| (span, "type in trait".to_owned())),
trait_c_span.map(|span| (span, Cow::from("type in trait"))),
Some(infer::ValuePairs::Terms(ExpectedFound {
expected: trait_ty.into(),
found: impl_ty.into(),

9
compiler/rustc_hir_analysis/src/check/intrinsic.rs
View file

@ -121,10 +121,11 @@ pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: DefId) -> hir
if has_safe_attr != is_in_list {
tcx.sess.struct_span_err(
tcx.def_span(intrinsic_id),
DiagnosticMessage::Str(format!(
"intrinsic safety mismatch between list of intrinsics within the compiler and core library intrinsics for intrinsic `{}`",
tcx.item_name(intrinsic_id)
))).emit();
DiagnosticMessage::from(format!(
"intrinsic safety mismatch between list of intrinsics within the compiler and core library intrinsics for intrinsic `{}`",
tcx.item_name(intrinsic_id)
)
)).emit();
}
is_in_list