Structurally resolve correctly in check_pat_lit

Author: compiler-errors

compiler/rustc_hir_typeck/src/pat.rs

@@ -393,9 +393,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // They can denote both statically and dynamically-sized byte arrays.
         let mut pat_ty = ty;
         if let hir::ExprKind::Lit(Spanned { node: ast::LitKind::ByteStr(..), .. }) = lt.kind {
-            let expected = self.structurally_resolved_type(span, expected);
-            if let ty::Ref(_, inner_ty, _) = expected.kind()
-                && matches!(inner_ty.kind(), ty::Slice(_))
+            if let ty::Ref(_, inner_ty, _) = *self.structurally_resolved_type(span, expected).kind()
+                && self.structurally_resolved_type(span, inner_ty).is_slice()
             {
                 let tcx = self.tcx;
                 trace!(?lt.hir_id.local_id, "polymorphic byte string lit");

tests/ui/traits/new-solver/slice-match-byte-lit.rs

@@ -0,0 +1,11 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+fn test(s: &[u8]) {
+    match &s[0..3] {
+        b"uwu" => {}
+        _ => {}
+    }
+}
+
+fn main() {}