Avoid creating an unused HirId

Author: camelid

compiler/rustc_ast_lowering/src/lib.rs

@@ -1174,7 +1174,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn lower_anon_const_as_const_arg(&mut self, anon: &AnonConst) -> hir::ConstArg<'hir> {
-        if let ExprKind::Path(qself, path) = &anon.value.kind {
+        if let ExprKind::Path(qself, path) = &anon.value.kind
+            && let Some(res) = self
+                .resolver
+                .get_partial_res(anon.id)
+                .and_then(|partial_res| partial_res.full_res())
+            // FIXME(min_generic_const_exprs): for now we only lower params to ConstArgKind::Path
+            && let Res::Def(DefKind::ConstParam, _) = res
+        {
             let qpath = self.lower_qpath(
                 anon.id,
                 qself,
@@ -1183,18 +1190,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                 None,
             );
-            // FIXME(min_generic_const_exprs): for now we only lower params to ConstArgKind::Path
-            if let hir::QPath::Resolved(
-                _,
-                &hir::Path { res: Res::Def(DefKind::ConstParam, _), .. },
-            ) = qpath
-            {
-                return ConstArg {
-                    hir_id: self.lower_node_id(anon.id),
-                    kind: ConstArgKind::Path(qpath),
-                    is_desugared_from_effects: false,
-                };
-            }
+            return ConstArg {
+                hir_id: self.lower_node_id(anon.id),
+                kind: ConstArgKind::Path(qpath),
+                is_desugared_from_effects: false,
+            };
         }
 
         let lowered_anon = self.lower_anon_const(anon);
@@ -2599,12 +2599,11 @@ impl<'hir> GenericArgsCtor<'hir> {
             return;
         }
 
-        let id = lcx.next_node_id();
-        let hir_id = lcx.next_id();
-
-        let const_arg_kind = match constness {
+        let (hir_id, const_arg_kind) = match constness {
             BoundConstness::Never => return,
             BoundConstness::Always(span) => {
+                let id = lcx.next_node_id();
+                let hir_id = lcx.next_id();
                 let span = lcx.lower_span(span);
 
                 let body = hir::ExprKind::Lit(
@@ -2621,14 +2620,18 @@ impl<'hir> GenericArgsCtor<'hir> {
                 );
 
                 lcx.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
-                hir::ConstArgKind::Anon(lcx.arena.alloc(hir::AnonConst {
-                    def_id,
+                (
                     hir_id,
-                    body,
-                    span,
-                }))
+                    hir::ConstArgKind::Anon(lcx.arena.alloc(hir::AnonConst {
+                        def_id,
+                        hir_id,
+                        body,
+                        span,
+                    })),
+                )
             }
             BoundConstness::Maybe(span) => {
+                let hir_id = lcx.next_id();
                 let span = lcx.lower_span(span);
 
                 let Some(host_param_id) = lcx.host_param_id else {
@@ -2652,7 +2655,7 @@ impl<'hir> GenericArgsCtor<'hir> {
                         )
                     ],
                 });
-                hir::ConstArgKind::Path(hir::QPath::Resolved(None, path))
+                (hir_id, hir::ConstArgKind::Path(hir::QPath::Resolved(None, path)))
             }
         };