Querify unused trait check.

compiler/rustc_hir_analysis/src/check_unused.rs

@@ -1,11 +1,16 @@
 use rustc_data_structures::unord::{ExtendUnord, UnordSet};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
+use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::lint;
 
-pub fn check_crate(tcx: TyCtxt<'_>) {
-    let mut used_trait_imports: UnordSet<LocalDefId> = Default::default();
+pub fn provide(providers: &mut Providers) {
+    *providers = Providers { check_unused_traits, ..*providers };
+}
+
+fn check_unused_traits(tcx: TyCtxt<'_>, (): ()) {
+    let mut used_trait_imports = UnordSet::<LocalDefId>::default();
 
     // FIXME: Use `tcx.hir().par_body_owners()` when we implement creating `DefId`s
     // for anon constants during their parents' typeck.

compiler/rustc_hir_analysis/src/lib.rs

@@ -177,6 +177,7 @@ pub fn provide(providers: &mut Providers) {
     collect::provide(providers);
     coherence::provide(providers);
     check::provide(providers);
+    check_unused::provide(providers);
     variance::provide(providers);
     outlives::provide(providers);
     impl_wf_check::provide(providers);
@@ -247,7 +248,7 @@ pub fn check_crate(tcx: TyCtxt<'_>) -> Result<(), ErrorGuaranteed> {
         }
     });
 
-    check_unused::check_crate(tcx);
+    tcx.ensure().check_unused_traits(());
 
     if let Some(reported) = tcx.sess.has_errors() { Err(reported) } else { Ok(()) }
 }

compiler/rustc_middle/src/query/mod.rs

@@ -898,6 +898,10 @@
         desc { |tcx| "linting {}", describe_as_module(key, tcx) }
     }
 
+    query check_unused_traits(_: ()) -> () {
+        desc { "checking unused trait imports in crate" }
+    }
+
     /// Checks the attributes in the module.
     query check_mod_attrs(key: LocalDefId) -> () {
         desc { |tcx| "checking attributes in {}", describe_as_module(key, tcx) }

tests/incremental/hashes/trait_defs.rs

@@ -426,7 +426,7 @@ trait TraitAddExternModifier {
 #[cfg(not(any(cfail1,cfail4)))]
 #[rustc_clean(cfg="cfail2")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(except="hir_owner", cfg="cfail5")]
+#[rustc_clean(cfg="cfail5")]
 #[rustc_clean(cfg="cfail6")]
 trait TraitAddExternModifier {
     #[rustc_clean(except="hir_owner,hir_owner_nodes,fn_sig", cfg="cfail2")]