Use different hir ids for ConstArg and InferArg

Author: voidc

compiler/rustc_ast_lowering/src/lib.rs

@@ -2034,13 +2034,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         match c.value.kind {
             ExprKind::Underscore => {
                 if self.tcx.features().generic_arg_infer() {
-                    let hir_id = self.lower_node_id(c.id);
                     let ct_kind = hir::ConstArgKind::Infer(hir::InferArg {
-                        hir_id,
+                        hir_id: self.lower_node_id(c.id),
                         span: self.lower_span(c.value.span),
                     });
-                    // FIXME(void): should InferArg and ConstArg share the same hir_id?
-                    self.arena.alloc(hir::ConstArg { hir_id, kind: ct_kind })
+                    self.arena.alloc(hir::ConstArg { hir_id: self.next_id(), kind: ct_kind })
                 } else {
                     feature_err(
                         &self.tcx.sess,