From 7727fbe6684ff12815f84085dd078074f9bd22de Mon Sep 17 00:00:00 2001
From: crumbtoo <crumb@disroot.org>
Date: Fri, 15 Mar 2024 18:47:52 -0600
Subject: [PATCH] correctly apply substs

---
 src/Rlp/HindleyMilner.hs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Rlp/HindleyMilner.hs b/src/Rlp/HindleyMilner.hs
index 7b72730..9696300 100644
--- a/src/Rlp/HindleyMilner.hs
+++ b/src/Rlp/HindleyMilner.hs
@@ -136,7 +136,7 @@ infer1' g1 e = do
     ((t,j) :< _) <- annotate e
     g2 <- unify (j ^. constraints)
     g <- unionContextWithKeyM unifyTypes g1 g2
-    pure $ ifoldlOf (contextVars . itraversed) subst t g
+    pure $ ifoldrOf (contextVars . itraversed) subst t g
   where
     -- intuitively, we'd return mgu(s,t) but the union is left-biased making `s`
     -- the user-specified type: prioritise her.
@@ -211,6 +211,7 @@ typeCheckRlpProgR p = tc p
     etaExpandAll = programDecls . each %~ etaExpand
 
 etaExpand :: Decl b (RlpExpr b) -> Decl b (RlpExpr b)
+etaExpand (FunD n [] e) = FunD n [] e
 etaExpand (FunD n as e)
     | Right as' <- allVarP as
     = FunD n [] (Finl . LamF as' $ e)