rustdoc: Avoid ICE on unevaluated type const projections in array lengths

Author: lapla-cogito

src/librustdoc/clean/mod.rs

@@ -2152,7 +2152,10 @@ pub(crate) fn clean_middle_ty<'tcx>(
             format!("{pat:?}").into_boxed_str(),
         ),
         ty::Array(ty, n) => {
-            let n = cx.tcx.normalize_erasing_regions(cx.typing_env(), Unnormalized::new_wip(n));
+            let n = cx
+                .tcx
+                .try_normalize_erasing_regions(cx.typing_env(), Unnormalized::new_wip(n))
+                .unwrap_or(n);
             let n = print_const(cx.tcx, n);
             Array(Box::new(clean_middle_ty(bound_ty.rebind(ty), cx, None, None)), n.into())
         }

src/librustdoc/clean/utils.rs

@@ -351,8 +351,16 @@ pub(crate) fn name_from_pat(p: &hir::Pat<'_>) -> Symbol {
 pub(crate) fn print_const(tcx: TyCtxt<'_>, n: ty::Const<'_>) -> String {
     match n.kind() {
         ty::ConstKind::Unevaluated(ty::UnevaluatedConst { kind, .. }) => match kind {
-            ty::UnevaluatedConstKind::Projection { def_id }
-            | ty::UnevaluatedConstKind::Inherent { def_id }
+            ty::UnevaluatedConstKind::Projection { def_id } => {
+                if let Some(local_def_id) = def_id.as_local()
+                    && let Some(body_id) = tcx.hir_maybe_body_owned_by(local_def_id)
+                {
+                    rendered_const(tcx, body_id, local_def_id)
+                } else {
+                    n.to_string()
+                }
+            }
+            ty::UnevaluatedConstKind::Inherent { def_id }
             | ty::UnevaluatedConstKind::Free { def_id }
             | ty::UnevaluatedConstKind::Anon { def_id } => {
                 if let Some(local_def_id) = def_id.as_local()

tests/rustdoc-html/type-const-associated-const-no-body.rs

@@ -0,0 +1,20 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/149287>
+//! and <https://github.com/rust-lang/rust/issues/158155>
+
+#![crate_name = "foo"]
+#![feature(min_generic_const_args)]
+#![expect(incomplete_features)]
+
+pub trait Tr {
+    type const SIZE: usize;
+}
+
+//@ has 'foo/fn.mk_array.html'
+//@ has - '//pre[@class="rust item-decl"]/code' '[(); <T as Tr>::SIZE]'
+pub fn mk_array<T: Tr>() -> [(); <T as Tr>::SIZE] {
+    [(); T::SIZE]
+}
+
+//@ has 'foo/type.Arr.html'
+//@ has - '//pre[@class="rust item-decl"]/code' '[(); <T as Tr>::SIZE]'
+pub type Arr<T> = [(); <T as Tr>::SIZE];