From b995a55cafcbcafec51aba6c567b32161fa9c2f1 Mon Sep 17 00:00:00 2001
From: Cameron Steffen <cam.steffen94@gmail.com>
Date: Wed, 13 Aug 2025 14:36:13 -0500
Subject: [PATCH] Don't store defaultness for inherent impl items

---
 compiler/rustc_metadata/src/rmeta/encoder.rs     | 5 ++++-
 compiler/rustc_middle/src/query/mod.rs           | 1 +
 compiler/rustc_middle/src/ty/assoc.rs            | 5 ++++-
 compiler/rustc_ty_utils/src/ty.rs                | 4 ----
 src/librustdoc/clean/mod.rs                      | 5 ++++-
 src/librustdoc/passes/collect_intra_doc_links.rs | 2 +-
 6 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index cb603705ce14..db66938457f0 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1725,7 +1725,10 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         let tcx = self.tcx;
         let item = tcx.associated_item(def_id);
 
-        self.tables.defaultness.set_some(def_id.index, item.defaultness(tcx));
+        if matches!(item.container, AssocContainer::Trait | AssocContainer::TraitImpl(_)) {
+            self.tables.defaultness.set_some(def_id.index, item.defaultness(tcx));
+        }
+
         record!(self.tables.assoc_container[def_id] <- item.container);
 
         if let AssocContainer::Trait = item.container
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 2aa32dfa0d82..0e645a3aae45 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1881,6 +1881,7 @@ rustc_queries! {
     }
 
     /// Returns whether the impl or associated function has the `default` keyword.
+    /// Note: This will ICE on inherent impl items. Consider using `AssocItem::defaultness`.
     query defaultness(def_id: DefId) -> hir::Defaultness {
         desc { |tcx| "looking up whether `{}` has `default`", tcx.def_path_str(def_id) }
         separate_provide_extern
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index 60181783f9b1..768646c76302 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -53,7 +53,10 @@ impl AssocItem {
     ///
     /// [`type_of`]: crate::ty::TyCtxt::type_of
     pub fn defaultness(&self, tcx: TyCtxt<'_>) -> hir::Defaultness {
-        tcx.defaultness(self.def_id)
+        match self.container {
+            AssocContainer::InherentImpl => hir::Defaultness::Final,
+            AssocContainer::Trait | AssocContainer::TraitImpl(_) => tcx.defaultness(self.def_id),
+        }
     }
 
     pub fn expect_trait_impl(&self) -> Result<DefId, ErrorGuaranteed> {
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index b3f2bb6d4b5a..a5987757dc34 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -93,10 +93,6 @@ fn defaultness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Defaultness {
             ..
         })
         | hir::Node::TraitItem(hir::TraitItem { defaultness, .. }) => *defaultness,
-        hir::Node::ImplItem(hir::ImplItem {
-            impl_kind: hir::ImplItemImplKind::Inherent { .. },
-            ..
-        }) => hir::Defaultness::Final,
         node => {
             bug!("`defaultness` called on {:?}", node);
         }
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 8c40e42562cf..5ccacafea015 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1256,7 +1256,10 @@ pub(crate) fn clean_impl_item<'tcx>(
             })),
             hir::ImplItemKind::Fn(ref sig, body) => {
                 let m = clean_function(cx, sig, impl_.generics, ParamsSrc::Body(body));
-                let defaultness = cx.tcx.defaultness(impl_.owner_id);
+                let defaultness = match impl_.impl_kind {
+                    hir::ImplItemImplKind::Inherent { .. } => hir::Defaultness::Final,
+                    hir::ImplItemImplKind::Trait { defaultness, .. } => defaultness,
+                };
                 MethodItem(m, Some(defaultness))
             }
             hir::ImplItemKind::Type(hir_ty) => {
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 719b7c6ab89c..0da42f38251c 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -210,7 +210,7 @@ impl UrlFragment {
             &UrlFragment::Item(def_id) => {
                 let kind = match tcx.def_kind(def_id) {
                     DefKind::AssocFn => {
-                        if tcx.defaultness(def_id).has_value() {
+                        if tcx.associated_item(def_id).defaultness(tcx).has_value() {
                             "method."
                         } else {
                             "tymethod."