From 8336211a4b0ec4b93e869bfafaa56f2e017185e8 Mon Sep 17 00:00:00 2001
From: Greg Shuflin <greg.shuflin@protonmail.com>
Date: Tue, 2 Nov 2021 21:03:48 -0700
Subject: [PATCH] Disallow functions with more than 255 arguments

---
 schala-lang/language/src/parsing/mod.rs           |  8 +++++++-
 schala-lang/language/src/parsing/test.rs          | 12 +++++++++++-
 schala-lang/language/src/symbol_table/resolver.rs |  2 +-
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/schala-lang/language/src/parsing/mod.rs b/schala-lang/language/src/parsing/mod.rs
index f5bee46..84f93b5 100644
--- a/schala-lang/language/src/parsing/mod.rs
+++ b/schala-lang/language/src/parsing/mod.rs
@@ -562,7 +562,13 @@ impl Parser {
 
     #[recursive_descent_method]
     fn formal_param_list(&mut self) -> ParseResult<Vec<FormalParam>> {
-        Ok(delimited!(self, LParen, formal_param, Comma, RParen))
+        let tok = self.token_handler.peek();
+        let list = delimited!(self, LParen, formal_param, Comma, RParen);
+        if list.len() > 255 {
+            ParseError::new_with_token("A function cannot have more than 255 arguments", tok.clone())
+        } else {
+            Ok(list)
+        }
     }
 
     #[recursive_descent_method]
diff --git a/schala-lang/language/src/parsing/test.rs b/schala-lang/language/src/parsing/test.rs
index fe78bdf..2d201a4 100644
--- a/schala-lang/language/src/parsing/test.rs
+++ b/schala-lang/language/src/parsing/test.rs
@@ -2,7 +2,7 @@
 #![allow(clippy::upper_case_acronyms)]
 #![allow(clippy::vec_init_then_push)]
 //use test_case::test_case;
-use std::rc::Rc;
+use std::{fmt::Write, rc::Rc};
 
 use pretty_assertions::assert_eq;
 
@@ -788,6 +788,16 @@ fn functions() {
     );
 }
 
+#[test]
+fn max_function_params() {
+    let mut buf = "fn longfunc(".to_string();
+    for n in 0..256 {
+        write!(buf, "a{}, ", n).unwrap();
+    }
+    write!(buf, ") {{ return 20 }}").unwrap();
+    assert_fail!(&buf, "A function cannot have more than 255 arguments");
+}
+
 #[test]
 fn functions_with_different_whitespace() {
     use ExpressionKind::*;
diff --git a/schala-lang/language/src/symbol_table/resolver.rs b/schala-lang/language/src/symbol_table/resolver.rs
index c2c1aff..32f7ca1 100644
--- a/schala-lang/language/src/symbol_table/resolver.rs
+++ b/schala-lang/language/src/symbol_table/resolver.rs
@@ -9,7 +9,7 @@ use crate::{
 #[derive(Debug)]
 enum NameType {
     //TODO eventually this needs to support closures
-    Param(u8), //TODO handle implications of functions being limited to 255 params
+    Param(u8),
     LocalVariable(ItemId),
     LocalFunction(ItemId),
     Import(Fqsn),