From cfdddbb00236770e7f621deffb2f63ed40573df1 Mon Sep 17 00:00:00 2001
From: Steve Dunham <dunhamsteve@gmail.com>
Date: Wed, 18 Mar 2026 17:28:58 -0700
Subject: [PATCH] cons/nil for pair/unit in scheme backend

---
 Makefile                 |  2 +-
 prim.ss                  |  5 ++---
 src/Lib/CompileExp.newt  |  6 ------
 src/Lib/ProcessDecl.newt | 13 ++++++++-----
 4 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/Makefile b/Makefile
index 458431f..5e75b82 100644
--- a/Makefile
+++ b/Makefile
@@ -25,7 +25,7 @@ newt3.js: newt2.js
 newt.ss: newt.js
 	$(RUNJS) newt.js src/Main.newt -o newt.ss
 
-newt.so: newt.ss
+newt.so: newt.ss prim.ss
 	chez --script scripts/compile-chez.ss
 
 test: newt.js
diff --git a/prim.ss b/prim.ss
index 7386c4c..e4a780e 100644
--- a/prim.ss
+++ b/prim.ss
@@ -1,9 +1,8 @@
 ;; REVIEW all of this - some of it is IO and needs the IO dance
 ;; maybe we make a helper? A macro?
 
-(define $Nil (lambda (nm-0) (vector 0 nm-0)))
-(define $Cons (lambda (nm-0 nm-1 nm-2) (vector 1 nm-0 nm-1 nm-2)))
-(define $IORes (lambda (nm-1 nm-2) (vector 0 #f nm-1 nm-2)))
+; (define $IORes (lambda (nm-1 nm-2) (vector 0 #f nm-1 nm-2)))
+(define $IORes (lambda (nm-1 nm-2) (cons nm-1 nm-2)))
 (define ($Left x) (vector 0 #f #f x))
 (define ($Right x) (vector 1 #f #f x))
 (define $LT 0)
diff --git a/src/Lib/CompileExp.newt b/src/Lib/CompileExp.newt
index 979671e..ef22d84 100644
--- a/src/Lib/CompileExp.newt
+++ b/src/Lib/CompileExp.newt
@@ -146,12 +146,6 @@ compileTerm tm@(App _ _ _) = case funArgs tm of
             if length' qs == length' args
               then pure $ CConstr tag nm.baseName args' qs NilCon
               else apply nm args' arity
-          -- REVIEW Slower for JS, faster for scheme. (2.88 vs 3.01)
-          -- but all of the "JS" diff is code gen?
-          -- Just (DCon tag info qs _) =>
-          --   if length' qs == length' args
-          --     then pure $ CConstr tag nm.baseName args' qs info
-          --     else apply nm args' arity
           _ => apply nm args' arity
   -- REVIEW maybe we want a different constructor for non-Ref applications?
   (t, args) => do
diff --git a/src/Lib/ProcessDecl.newt b/src/Lib/ProcessDecl.newt
index 40fa641..3c98095 100644
--- a/src/Lib/ProcessDecl.newt
+++ b/src/Lib/ProcessDecl.newt
@@ -415,11 +415,14 @@ populateConInfo entries =
     -- Boolean
     | Just (a :: b :: Nil) => (setInfo a FalseCon :: setInfo b TrueCon :: Nil)
     | Just entries => entries in
-  let (a :: b :: Nil) = entries | _ => entries in
-  fromMaybe entries $ checkNat entries <|> checkCons entries
-  -- let (Nothing) = checkNat entries | Just entries => entries in
-  -- let (Nothing) = checkNat entries | Just entries => entries in
-  -- entries
+  case entries of
+    a :: Nil => case countFields a of
+      0 => setInfo a NilCon :: Nil
+      2 => setInfo a ConsCon :: Nil
+      _ => entries
+    a :: b :: Nil =>
+      fromMaybe entries $ checkNat entries <|> checkCons entries
+    _ => entries
   where
     countFields : TopEntry → Int
     countFields (MkEntry fc name type def eflags) = go type