From 929ae557ed092e53aaf46588fd34e86abe402d44 Mon Sep 17 00:00:00 2001
From: Nat Quayle Nelson <natquaylenelson@gmail.com>
Date: Fri, 8 Aug 2025 12:10:11 -0500
Subject: [PATCH] allow :Null on lambda and arrow lambda

---
 src/kiss/Reader.hx       | 11 +++++++++--
 src/kiss/SpecialForms.hx |  5 ++++-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/kiss/Reader.hx b/src/kiss/Reader.hx
index 33496a1..a531938 100644
--- a/src/kiss/Reader.hx
+++ b/src/kiss/Reader.hx
@@ -178,7 +178,7 @@ class Reader {
         //     -+>countVar arg body
         //     -+>countVar {body}
         //     -+>countVar (body)
-        // or any of those with the first expression after -> or -+> prefixed by :Void
+        // or any of those with the first expression after -> or -+> prefixed by :Void or :Null
         function arrowSyntax(countingLambda:Bool, stream:Stream, k:HasReadTables) {
             var countVar = if (countingLambda) {
                 _assertRead(stream, k);
@@ -192,10 +192,14 @@ class Reader {
             var bodyExp:ReaderExp = null;
 
             var returnsValue = true;
+            var returnsNull = false;
             switch (firstExp.def) {
                 case TypedExp("Void", realFirstExp):
                     firstExp = realFirstExp;
                     returnsValue = false;
+                case TypedExp("Null", realFirstExp):
+                    firstExp = realFirstExp;
+                    returnsNull = true;
                 default:
             }
             switch (firstExp.def) {
@@ -209,10 +213,13 @@ class Reader {
                     argsExp = b.list([]);
                     bodyExp = firstExp;
                 default:
-                    throw KissError.fromExp(firstExp, "first expression after -> should be [args...], arg, (exp) or {body}, or one of those prefixed with :Void. When an argument type must be specified, even a single argument name must be put in brackets. For example: ->[:ArgType arg] <exp>");
+                    throw KissError.fromExp(firstExp, "first expression after -> should be [args...], arg, (exp) or {body}, or one of those prefixed with :Void or :Null. When an argument type must be specified, even a single argument name must be put in brackets. For example: ->[:ArgType arg] <exp>");
             }
             if (!returnsValue) {
                 argsExp = TypedExp("Void", argsExp).withPosOf(argsExp);
+            } else if(returnsNull) {
+                argsExp = TypedExp("Null", argsExp).withPosOf(argsExp);
+                bodyExp = b.begin([bodyExp, b.callSymbol("return", [b.symbol("null")])]);
             }
             return if (countingLambda) {
                 CallExp(b.symbol("countingLambda"), [countVar, argsExp, bodyExp]);
diff --git a/src/kiss/SpecialForms.hx b/src/kiss/SpecialForms.hx
index 835d50d..4e731b2 100644
--- a/src/kiss/SpecialForms.hx
+++ b/src/kiss/SpecialForms.hx
@@ -271,12 +271,15 @@ class SpecialForms {
             block;
         };
 
-        k.doc("lambda", 2, null, "(lambda [<argsNames...>] <body...>)");
+        k.doc("lambda", 2, null, "(lambda  <optional :Void or :Null> [<argsNames...>] <body...>)");
         map["lambda"] = (wholeExp:ReaderExp, args:Array<ReaderExp>, k:KissState) -> {
             var returnsValue = switch (args[0].def) {
                 case TypedExp("Void", argNames):
                     args[0] = argNames;
                     false;
+                case TypedExp("Null", argNames):
+                    args[0] = argNames;
+                    true;
                 default:
                     true;
             }