From b9a80d8bbc568ae8e995fde0ea1710359ab4ab1c Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Mon, 18 Oct 2021 16:32:39 +0200
Subject: Fix a bug with too early binding of parameters

---
 src/bootstrap/objects.h    |  2 +-
 src/bootstrap/primitives.c | 24 +++++++++++++++++++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

(limited to 'src/bootstrap')

diff --git a/src/bootstrap/objects.h b/src/bootstrap/objects.h
index 56821eb..cba6f10 100644
--- a/src/bootstrap/objects.h
+++ b/src/bootstrap/objects.h
@@ -56,7 +56,7 @@ typedef struct Object {
 
 // Object constructors.
 Object * make_fixnum(ssize_t num);
-Object * make_procedure(Object *(*proc)(struct Environment *, struct Object *args));
+Object * make_procedure(Object *(*proc)(struct Environment *, Object *args));
 Object * make_pair(Object *car, Object *cdr);
 Object * make_symbol(StringView sv);
 Object * make_string(void);
diff --git a/src/bootstrap/primitives.c b/src/bootstrap/primitives.c
index 0f1498d..7ac9bf7 100644
--- a/src/bootstrap/primitives.c
+++ b/src/bootstrap/primitives.c
@@ -104,6 +104,12 @@ eval_lambda:
                 // Extend environment.
                 env = env_extend(tmp, env);
             }
+
+            // Create temporary environment to store bindings.
+            Environment *tmp = env_create(env);
+            push_active_env(tmp);
+
+            // Evaluate arguments in temporary environment.
             while (params != obj_nil) {
                 if (args == obj_nil) {
                     error_push((Error){
@@ -124,7 +130,7 @@ eval_lambda:
                     });
                     return obj_err;
                 }
-                env_add_or_update_current(env, symbol, value);
+                env_add_or_update_current(tmp, symbol, value);
                 args = args->cdr;
                 params = params->cdr;
             }
@@ -135,6 +141,22 @@ eval_lambda:
                 });
                 return obj_err;
             }
+
+            // Copy temporary environment values to closure environment.
+            args = root->cdr;
+            params = lambda->params;
+            while (params != obj_nil) {
+                Object *symbol = params->car;
+                Object *value = env_lookup(tmp, symbol);
+                env_add_or_update_current(env, symbol, value);
+                args = args->cdr;
+                params = params->cdr;
+            }
+
+            // Release the temporary environment protection.
+            pop_active_env();
+
+            // Run the body of the function.
             root = lambda->body;
             while (root->cdr != obj_nil) {
                 if (eval(env, root->car) == obj_err) {
-- 
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