From 19e30b10f95979d6473404ac18983e91caa4cc82 Mon Sep 17 00:00:00 2001
From: KtorZ <matthias.benkort@gmail.com>
Date: Fri, 6 Sep 2024 12:27:53 +0200
Subject: [PATCH] Fix #1013

---
 CHANGELOG.md                        | 14 ++++++++++++++
 crates/aiken-lang/src/tipo/error.rs |  8 ++++----
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4b3436bf..12fd0a31 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,19 @@
 # Changelog
 
+## v1.1.1 - UNRELEASED
+
+### Added
+
+- N/A
+
+### Changed
+
+- **aiken-lang**: Fix underflow in error message reported by the validator arity. See [#1013](https://github.com/aiken-lang/aiken/issues/1013) @KtorZ.
+
+### Removed
+
+- N/A
+
 ## v1.1.0 - 2024-09-03
 
 ### Added
diff --git a/crates/aiken-lang/src/tipo/error.rs b/crates/aiken-lang/src/tipo/error.rs
index 2454daa0..2ed3a0fd 100644
--- a/crates/aiken-lang/src/tipo/error.rs
+++ b/crates/aiken-lang/src/tipo/error.rs
@@ -982,9 +982,9 @@ The best thing to do from here is to remove it."#))]
     #[error("Validators require at least 2 arguments and at most 3 arguments.\n")]
     #[diagnostic(code("illegal::validator_arity"))]
     #[diagnostic(help(
-        "Please {}.\nIf you don't need one of the required arguments use an underscore (e.g. `_datum`).",
-        if *count < 2 {
-            let missing = 2 - count;
+        "Please {}. If you don't need one of the required arguments use an underscore (e.g. `_datum`).",
+        if *count < *expected {
+            let missing = expected - count;
 
             let mut arguments = "argument".to_string();
 
@@ -997,7 +997,7 @@ The best thing to do from here is to remove it."#))]
                 missing.to_string().if_supports_color(Stdout, |s| s.yellow()),
             )
         } else {
-            let extra = count - 3;
+            let extra = count - expected;
 
             let mut arguments = "argument".to_string();