From a5351a88aeced58f782ebe9f8508dbe9d6febba4 Mon Sep 17 00:00:00 2001
From: Alex van de Sandt <alex@avandesa.dev>
Date: Sun, 30 Jun 2024 17:37:36 -0400
Subject: [PATCH] Pass function args through child env

---
 src/callable.rs    | 18 ++++++++----------
 src/interpreter.rs | 14 ++++++++++----
 2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/src/callable.rs b/src/callable.rs
index 7810f1d..159f6e2 100644
--- a/src/callable.rs
+++ b/src/callable.rs
@@ -8,14 +8,16 @@ use crate::{environment::Env, interpreter::RuntimeError, value::Value};
 type CallableOutput = Result<Value, RuntimeError>;
 
 pub trait Callable: Debug {
-    fn arity(&self) -> usize;
-    fn call(&self, env: &Env, args: &[Value]) -> CallableOutput;
+    fn params(&self) -> Vec<String> {
+        Vec::new()
+    }
+    fn call(&self, env: &Env) -> CallableOutput;
 }
 
 pub struct NativeFunction {
     arity: usize,
     #[allow(clippy::type_complexity)]
-    implementation: Box<dyn Fn(&Env, &[Value]) -> CallableOutput>,
+    implementation: Box<dyn Fn(&Env) -> CallableOutput>,
 }
 
 impl NativeFunction {
@@ -26,7 +28,7 @@ impl NativeFunction {
     pub fn clock() -> Self {
         Self {
             arity: 0,
-            implementation: Box::new(|_, _| {
+            implementation: Box::new(|_| {
                 let now = SystemTime::now()
                     .duration_since(SystemTime::UNIX_EPOCH)
                     .unwrap()
@@ -38,12 +40,8 @@ impl NativeFunction {
 }
 
 impl Callable for NativeFunction {
-    fn arity(&self) -> usize {
-        self.arity
-    }
-
-    fn call(&self, env: &Env, args: &[Value]) -> Result<Value, RuntimeError> {
-        (self.implementation)(env, args)
+    fn call(&self, env: &Env) -> Result<Value, RuntimeError> {
+        (self.implementation)(env)
     }
 }
 
diff --git a/src/interpreter.rs b/src/interpreter.rs
index ce7f251..b71e87d 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -152,7 +152,8 @@ impl<Output: Write> Interpreter<Output> {
                 };
 
                 // Check the arity
-                if callable.arity() != arguments.len() {
+                let params = callable.params();
+                if params.len() != arguments.len() {
                     return Err(RuntimeError::incorrect_arity(
                         callable.as_ref(),
                         arguments.len(),
@@ -166,9 +167,14 @@ impl<Output: Write> Interpreter<Output> {
                     .map(|arg| Self::interpret_expr(arg, env))
                     .collect::<Result<Vec<_>, _>>()?;
 
+                // Define a new env for the call
+                let calling_env = env.new_child();
+                for (param, arg) in params.into_iter().zip(evaluated_args) {
+                    calling_env.define(param, arg)
+                }
+
                 // Call it
-                //Callable::call(call)
-                callable.call(env, &evaluated_args)
+                callable.call(&calling_env)
             }
         }
     }
@@ -388,7 +394,7 @@ impl RuntimeError {
 
     fn incorrect_arity(callable: &dyn Callable, args_len: usize, callee_span: Span) -> Self {
         Self::IncorrectArity {
-            expected: callable.arity(),
+            expected: callable.params().len(),
             actual: args_len,
             span: callee_span.into(),
         }
-- 
2.51.2