Stop requiring HIR for trait item wf checks

Author: oli-obk

compiler/rustc_hir_analysis/src/check/check.rs

@@ -37,7 +37,7 @@ use {rustc_attr_data_structures as attrs, rustc_hir as hir};
 use super::compare_impl_item::check_type_bounds;
 use super::*;
 use crate::check::wfcheck::{
-    check_variances_for_type_defn, check_where_clauses, enter_wf_checking_ctxt,
+    check_trait_item, check_variances_for_type_defn, check_where_clauses, enter_wf_checking_ctxt,
 };
 
 fn add_abi_diag_help<T: EmissionGuarantee>(abi: ExternAbi, diag: &mut Diag<'_, T>) {
@@ -981,10 +981,24 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(),
             tcx.ensure_ok().type_of(def_id);
             tcx.ensure_ok().fn_sig(def_id);
             tcx.ensure_ok().predicates_of(def_id);
+            let assoc_item = tcx.associated_item(def_id);
+            match assoc_item.container {
+                ty::AssocItemContainer::Impl => {}
+                ty::AssocItemContainer::Trait => {
+                    res = res.and(check_trait_item(tcx, def_id));
+                }
+            }
         }
         DefKind::AssocConst => {
             tcx.ensure_ok().type_of(def_id);
             tcx.ensure_ok().predicates_of(def_id);
+            let assoc_item = tcx.associated_item(def_id);
+            match assoc_item.container {
+                ty::AssocItemContainer::Impl => {}
+                ty::AssocItemContainer::Trait => {
+                    res = res.and(check_trait_item(tcx, def_id));
+                }
+            }
         }
         DefKind::AssocTy => {
             tcx.ensure_ok().predicates_of(def_id);
@@ -995,6 +1009,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(),
                 ty::AssocItemContainer::Trait => {
                     tcx.ensure_ok().item_bounds(def_id);
                     tcx.ensure_ok().item_self_bounds(def_id);
+                    res = res.and(check_trait_item(tcx, def_id));
                     assoc_item.defaultness(tcx).has_value()
                 }
             };

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -195,7 +195,7 @@ fn check_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGua
     res = res.and(match node {
         hir::Node::Crate(_) => bug!("check_well_formed cannot be applied to the crate root"),
         hir::Node::Item(item) => check_item(tcx, item),
-        hir::Node::TraitItem(item) => check_trait_item(tcx, item),
+        hir::Node::TraitItem(..) => Ok(()),
         hir::Node::ImplItem(item) => check_impl_item(tcx, item),
         hir::Node::ForeignItem(item) => check_foreign_item(tcx, item),
         hir::Node::ConstBlock(_) | hir::Node::Expr(_) | hir::Node::OpaqueTy(_) => Ok(()),
@@ -322,18 +322,16 @@ fn check_foreign_item<'tcx>(
     }
 }
 
-fn check_trait_item<'tcx>(
+pub(crate) fn check_trait_item<'tcx>(
     tcx: TyCtxt<'tcx>,
-    trait_item: &'tcx hir::TraitItem<'tcx>,
+    def_id: LocalDefId,
 ) -> Result<(), ErrorGuaranteed> {
-    let def_id = trait_item.owner_id.def_id;
-
     // Check that an item definition in a subtrait is shadowing a supertrait item.
     lint_item_shadowing_supertrait_item(tcx, def_id);
 
     let mut res = check_associated_item(tcx, def_id);
 
-    if matches!(trait_item.kind, hir::TraitItemKind::Fn(..)) {
+    if matches!(tcx.def_kind(def_id), DefKind::AssocFn) {
         for &assoc_ty_def_id in tcx.associated_types_for_impl_traits_in_associated_fn(def_id) {
             res = res.and(check_associated_item(tcx, assoc_ty_def_id.expect_local()));
         }

tests/incremental/cyclic-trait-hierarchy.rs

@@ -6,7 +6,7 @@
 pub trait T2 {}
 #[cfg(cfail2)]
 pub trait T2: T1 {}
-//[cfail2]~^ ERROR cycle detected when computing the implied predicates of `T2`
+//[cfail2]~^ ERROR cycle detected when computing the super predicates of `T2`
 
 pub trait T1: T2 {}