Auto merge of #118870 - Enselic:rustc_passes-query-stability, r=compiler-errors

rustc_passes: Enforce `rustc::potential_query_instability` lint
Stop allowing `rustc::potential_query_instability` in all of `rustc_passes` and instead allow it on a case-by-case basis if it is safe. In this case, all instances of the lint are safe to allow.
Part of #84447 which is E-help-wanted.

Author: bors

compiler/rustc_passes/src/diagnostic_items.rs

@@ -83,6 +83,9 @@ fn all_diagnostic_items(tcx: TyCtxt<'_>, (): ()) -> DiagnosticItems {
 
 // Collect diagnostic items in other crates.
 for&cnum in tcx.crates(()).iter().chain(std::iter::once(&LOCAL_CRATE)){
+// We are collecting many DiagnosticItems hash maps into one
+// DiagnosticItems hash map. The iteration order does not matter.
+#[allow(rustc::potential_query_instability)]
 for(&name,&def_id)in&tcx.diagnostic_items(cnum).name_to_id{
 collect_item(tcx,&mut items, name, def_id);
 }

compiler/rustc_passes/src/hir_stats.rs

@@ -121,6 +121,8 @@ impl<'k> StatCollector<'k> {
 }
 
 fnprint(&self,title:&str,prefix:&str){
+// We will soon sort, so the initial order does not matter.
+#[allow(rustc::potential_query_instability)]
 letmut nodes:Vec<_> = self.nodes.iter().collect();
  nodes.sort_by_key(|(_, node)| node.stats.count* node.stats.size);
 
@@ -147,6 +149,8 @@ impl<'k> StatCollector<'k> {
  to_readable_str(node.stats.size)
 );
 if !node.subnodes.is_empty(){
+// We will soon sort, so the initial order does not matter.
+#[allow(rustc::potential_query_instability)]
 letmut subnodes:Vec<_> = node.subnodes.iter().collect();
  subnodes.sort_by_key(|(_, subnode)| subnode.count* subnode.size);
 

compiler/rustc_passes/src/lib.rs

@@ -4,7 +4,6 @@
 //!
 //! This API is completely unstable and subject to change.
 
-#![allow(rustc::potential_query_instability)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]

compiler/rustc_passes/src/stability.rs

@@ -1048,6 +1048,9 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
  tcx.sess.emit_err(errors::UnknownFeature{ span,feature:*feature });
 }
 
+// We only use the hash map contents to emit errors, and the order of
+// emitted errors do not affect query stability.
+#[allow(rustc::potential_query_instability)]
 for(implied_by, feature)in remaining_implications {
 let local_defined_features = tcx.lib_features(LOCAL_CRATE);
 let span = local_defined_features