Address review comments

Author: camelid

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -2125,6 +2125,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 );
                 ty::Const::new_unevaluated(tcx, ty::UnevaluatedConst::new(did, args))
             }
+            // FIXME(const_generics): create real const to allow fn items as const paths
             Res::Def(DefKind::Fn | DefKind::AssocFn, _) => ty::Const::new_error_with_message(
                 tcx,
                 span,
@@ -2170,10 +2171,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             | Res::Local(_)
             | Res::ToolMod
             | Res::NonMacroAttr(_)
-            | Res::Err => Const::new_error(
-                tcx,
-                tcx.dcx().span_delayed_bug(span, "invalid Res for const path"),
-            ),
+            | Res::Err => Const::new_error_with_message(tcx, span, "invalid Res for const path"),
         }
     }
 

compiler/rustc_hir_analysis/src/lib.rs

@@ -230,7 +230,8 @@ pub fn lower_ty<'tcx>(tcx: TyCtxt<'tcx>, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> {
 }
 
 /// This is for rustdoc.
-pub fn lower_const_arg<'tcx>(
+// FIXME(const_generics): having special methods for rustdoc in `rustc_hir_analysis` is cursed
+pub fn lower_const_arg_for_rustdoc<'tcx>(
     tcx: TyCtxt<'tcx>,
     hir_ct: &hir::ConstArg<'tcx>,
     feed: FeedConstTy,

compiler/rustc_middle/src/ty/consts.rs

@@ -185,6 +185,7 @@ impl<'tcx> rustc_type_ir::inherent::Const<TyCtxt<'tcx>> for Const<'tcx> {
 }
 
 impl<'tcx> Const<'tcx> {
+    // FIXME: move this and try_from_lit to hir_ty_lowering like lower_const_arg/from_const_arg
     /// Literals and const generic parameters are eagerly converted to a constant, everything else
     /// becomes `Unevaluated`.
     #[instrument(skip(tcx), level = "debug")]

src/librustdoc/clean/mod.rs

@@ -43,7 +43,7 @@ use rustc_hir::PredicateOrigin;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, LOCAL_CRATE, LocalDefId};
 use rustc_hir_analysis::hir_ty_lowering::FeedConstTy;
-use rustc_hir_analysis::{lower_const_arg, lower_ty};
+use rustc_hir_analysis::{lower_const_arg_for_rustdoc, lower_ty};
 use rustc_middle::metadata::Reexport;
 use rustc_middle::middle::resolve_bound_vars as rbv;
 use rustc_middle::ty::{self, AdtKind, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt, TypingMode};
@@ -437,7 +437,7 @@ fn clean_hir_term<'tcx>(term: &hir::Term<'tcx>, cx: &mut DocContext<'tcx>) -> Te
     match term {
         hir::Term::Ty(ty) => Term::Type(clean_ty(ty, cx)),
         hir::Term::Const(c) => {
-            let ct = lower_const_arg(cx.tcx, c, FeedConstTy::No);
+            let ct = lower_const_arg_for_rustdoc(cx.tcx, c, FeedConstTy::No);
             Term::Constant(clean_middle_const(ty::Binder::dummy(ct), cx))
         }
     }
@@ -625,8 +625,9 @@ fn clean_generic_param<'tcx>(
         hir::GenericParamKind::Const { ty, default, synthetic } => {
             (param.name.ident().name, GenericParamDefKind::Const {
                 ty: Box::new(clean_ty(ty, cx)),
-                default: default
-                    .map(|ct| Box::new(lower_const_arg(cx.tcx, ct, FeedConstTy::No).to_string())),
+                default: default.map(|ct| {
+                    Box::new(lower_const_arg_for_rustdoc(cx.tcx, ct, FeedConstTy::No).to_string())
+                }),
                 synthetic,
             })
         }
@@ -1813,7 +1814,7 @@ pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> T
                     // `const_eval_poly` tries to first substitute generic parameters which
                     // results in an ICE while manually constructing the constant and using `eval`
                     // does nothing for `ConstKind::Param`.
-                    let ct = lower_const_arg(cx.tcx, const_arg, FeedConstTy::No);
+                    let ct = lower_const_arg_for_rustdoc(cx.tcx, const_arg, FeedConstTy::No);
                     let ct = if let hir::ConstArgKind::Anon(hir::AnonConst { def_id, .. }) =
                         const_arg.kind
                     {