Auto merge of rust-lang#81901 - Mark-Simulacrum:use-string-not-cow, r=jackh726

Switch query descriptions to just String

In practice we never used the borrowed variant anyway.

Author: bors

compiler/rustc_macros/src/query.rs

@@ -417,8 +417,8 @@ fn add_query_description_impl(
         fn describe(
             #tcx: TyCtxt<'tcx>,
             #key: #arg,
-        ) -> Cow<'static, str> {
-            ::rustc_middle::ty::print::with_no_trimmed_paths(|| format!(#desc).into())
+        ) -> String {
+            ::rustc_middle::ty::print::with_no_trimmed_paths(|| format!(#desc))
         }
     };
 

compiler/rustc_middle/src/query/mod.rs

@@ -13,7 +13,6 @@ use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_query_system::query::QueryDescription;
 
 use rustc_span::symbol::Symbol;
-use std::borrow::Cow;
 
 fn describe_as_module(def_id: LocalDefId, tcx: TyCtxt<'_>) -> String {
     if def_id.is_top_level_module() {

compiler/rustc_middle/src/ty/query/mod.rs

@@ -53,7 +53,6 @@ use rustc_ast as ast;
 use rustc_attr as attr;
 use rustc_span::symbol::Symbol;
 use rustc_span::{Span, DUMMY_SP};
-use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::ops::Deref;
 use std::path::PathBuf;

compiler/rustc_middle/src/ty/query/plumbing.rs

@@ -277,14 +277,14 @@ macro_rules! define_queries {
                 }
             }
 
-            pub fn describe(&self, tcx: TyCtxt<$tcx>) -> Cow<'static, str> {
+            pub fn describe(&self, tcx: TyCtxt<$tcx>) -> String {
                 let (r, name) = match *self {
                     $(Query::$name(key) => {
                         (queries::$name::describe(tcx, key), stringify!($name))
                     })*
                 };
                 if tcx.sess.verbose() {
-                    format!("{} [{}]", r, name).into()
+                    format!("{} [{}]", r, name)
                 } else {
                     r
                 }

compiler/rustc_query_system/src/query/config.rs

@@ -7,7 +7,6 @@ use crate::query::plumbing::CycleError;
 use crate::query::{QueryContext, QueryState};
 
 use rustc_data_structures::fingerprint::Fingerprint;
-use std::borrow::Cow;
 use std::fmt::Debug;
 use std::hash::Hash;
 
@@ -95,7 +94,7 @@ pub trait QueryAccessors<CTX: QueryContext>: QueryConfig {
 }
 
 pub trait QueryDescription<CTX: QueryContext>: QueryAccessors<CTX> {
-    fn describe(tcx: CTX, key: Self::Key) -> Cow<'static, str>;
+    fn describe(tcx: CTX, key: Self::Key) -> String;
 
     #[inline]
     fn cache_on_disk(_: CTX, _: &Self::Key, _: Option<&Self::Value>) -> bool {