2 files changed, 5 insertions, 1 deletions
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 6783bbf8bf4..413717e45eb 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -747,6 +747,9 @@ pub struct Ascription<'tcx> {
 
 #[derive(Clone, Debug, HashStable, TypeVisitable)]
 pub enum PatKind<'tcx> {
+    /// A missing pattern, e.g. for an anonymous param in a bare fn like `fn f(u32)`.
+    Missing,
+
     /// A wildcard pattern: `_`.
     Wild,
 
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index 7d62ab7970d..f3da2a5cc8e 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -250,7 +250,8 @@ pub(crate) fn for_each_immediate_subpat<'a, 'tcx>(
     mut callback: impl FnMut(&'a Pat<'tcx>),
 ) {
     match &pat.kind {
-        PatKind::Wild
+        PatKind::Missing
+        | PatKind::Wild
         | PatKind::Binding { subpattern: None, .. }
         | PatKind::Constant { value: _ }
         | PatKind::Range(_)