From a2f24fac65e779fbc7db37f29a9f00195bd8de1a Mon Sep 17 00:00:00 2001
From: Cameron Zwarich <cameron@lean-fro.org>
Date: Thu, 7 Aug 2025 08:23:01 -0700
Subject: [PATCH] chore: use `unreachable!` for unreachable cases, not silent
 fallback (#9790)

---
 src/Lean/Compiler/IR/RC.lean | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Lean/Compiler/IR/RC.lean b/src/Lean/Compiler/IR/RC.lean
index 9b4ac05fac..c4ff5c6a54 100644
--- a/src/Lean/Compiler/IR/RC.lean
+++ b/src/Lean/Compiler/IR/RC.lean
@@ -288,7 +288,7 @@ partial def visitFnBody (b : FnBody) (ctx : Context) : FnBody × LiveVarSet :=
     let bLiveVars := collectLiveVars b ctx.jpLiveVarMap
     ⟨b, bLiveVars⟩
   | .unreachable => ⟨.unreachable, {}⟩
-  | _ => ⟨b, {}⟩ -- unreachable if well-formed
+  | .set .. | .setTag .. | .inc .. | .dec .. | .del .. => unreachable!
 
 partial def visitDecl (env : Environment) (decls : Array Decl) (d : Decl) : Decl :=
   match d with