From 84bfdcf234a70daf8dc2d09fc4a1237448e54de0 Mon Sep 17 00:00:00 2001
From: Gavin Jaeger-Freeborn <gavinfreeborn@gmail.com>
Date: Thu, 2 Feb 2023 15:59:50 -0800
Subject: [PATCH] fix: Infinite loop when evaluating `(())` (#1427)

Evaluation of `(())` is treated as a malformed expression
rather than causing an infinite loop
---
 src/Eval.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Eval.hs b/src/Eval.hs
index 660b69a0..6dcf42d7 100644
--- a/src/Eval.hs
+++ b/src/Eval.hs
@@ -394,6 +394,7 @@ eval ctx xobj@(XObj o info ty) preference resolver =
     evaluateApp :: Evaluator
     evaluateApp (AppPat f' args) =
       case f' of
+        (ListPat []) -> pure (evalError ctx (format (GenericMalformed xobj)) (xobjInfo xobj))
         l@(ListPat _) -> go l ResolveLocal
         sym@(SymPat _ _) -> go sym resolver
         _ -> pure (evalError ctx (format (GenericMalformed xobj)) (xobjInfo xobj))