From 9d99eff6f90522a838551326e651bb6b660ca624 Mon Sep 17 00:00:00 2001
From: Trevor Elliott <telliott@fastly.com>
Date: Thu, 15 Sep 2022 10:40:37 -0700
Subject: [PATCH] Flatten `and` patterns in ISLE (#4915)

Flatten nested and patterns into a single vector in the ISLE front-end.
---
 cranelift/isle/isle/src/sema.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/cranelift/isle/isle/src/sema.rs b/cranelift/isle/isle/src/sema.rs
index 3da2441ed4..68c20097c0 100644
--- a/cranelift/isle/isle/src/sema.rs
+++ b/cranelift/isle/isle/src/sema.rs
@@ -1514,7 +1514,12 @@ impl TermEnv {
                         /* is_root = */ false,
                     ));
                     expected_ty = expected_ty.or(Some(ty));
-                    children.push(subpat);
+
+                    // Normalize nested `And` nodes to a single vector of conjuncts.
+                    match subpat {
+                        Pattern::And(_, subpat_children) => children.extend(subpat_children),
+                        _ => children.push(subpat),
+                    }
                 }
                 if expected_ty.is_none() {
                     tyenv.report_error(pos, "No type for (and ...) form.".to_string());