From 38f36ef2cef10ecc7620db9f0f3d46c92d23abc6 Mon Sep 17 00:00:00 2001
From: FineArchs <133759614+FineArchs@users.noreply.github.com>
Date: Tue, 14 May 2024 20:14:37 +0900
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* Update index.ts

* add test

* Update CHANGELOG.md
---
 CHANGELOG.md             |  2 ++
 src/interpreter/index.ts |  2 +-
 test/index.ts            | 10 ++++++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65815163..8d1626a9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,8 @@
 - `Uri:encode_full`, `Uri:encode_component`, `Uri:decode_full`, `Uri:decode_component`を追加
 - `str.starts_with`,`str.ends_with`を追加
 - `arr.splice`を追加
+- 関数の省略された引数にNULLを格納するように
+  - 一時的な措置であり、省略可能引数構文の実装と同時に廃止予定です。依存し過ぎないようにしてください
 
 # 0.18.0
 - `Core:abort`でプログラムを緊急停止できるように
diff --git a/src/interpreter/index.ts b/src/interpreter/index.ts
index 23df41ea..496e16ff 100644
--- a/src/interpreter/index.ts
+++ b/src/interpreter/index.ts
@@ -239,7 +239,7 @@ export class Interpreter {
 			for (let i = 0; i < (fn.args ?? []).length; i++) {
 				_args.set(fn.args![i]!, {
 					isMutable: true,
-					value: args[i]!,
+					value: args[i] ?? NULL,
 				});
 			}
 			const fnScope = fn.scope!.createChildScope(_args);
diff --git a/test/index.ts b/test/index.ts
index 18e215b9..91492317 100644
--- a/test/index.ts
+++ b/test/index.ts
@@ -1297,6 +1297,16 @@ describe('Function call', () => {
 		}
 		assert.fail();
 	});
+
+	test.concurrent('omitted args', async () => {
+		const res = await exe(`
+		@f(x, y) {
+			[x, y]
+		}
+		<: f(1)
+		`);
+		eq(res, ARR([NUM(1), NULL]));
+	});
 });
 
 describe('Return', () => {