From 74d4081f1be5001470bccff12b09d67c72b9ae1f Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Wed, 31 Jan 2024 10:15:00 +0530
Subject: [PATCH] checker: disallow `none` as match cond (#20688)

---
 vlib/v/checker/match.v                       | 3 +++
 vlib/v/checker/tests/none_match_cond_err.out | 5 +++++
 vlib/v/checker/tests/none_match_cond_err.vv  | 4 ++++
 3 files changed, 12 insertions(+)
 create mode 100644 vlib/v/checker/tests/none_match_cond_err.out
 create mode 100644 vlib/v/checker/tests/none_match_cond_err.vv

diff --git a/vlib/v/checker/match.v b/vlib/v/checker/match.v
index 57affaa8176ea0..b52e4983efa667 100644
--- a/vlib/v/checker/match.v
+++ b/vlib/v/checker/match.v
@@ -59,6 +59,9 @@ fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 			c.error('`match` expression with Option type only checks against `none`, to match its value you must unwrap it first `var?`',
 				branch.pos)
 		}
+		if cond_type_sym.kind == .none_ {
+			c.error('`none` cannot be a match condition', node.pos)
+		}
 		// If the last statement is an expression, return its type
 		if branch.stmts.len > 0 {
 			mut stmt := branch.stmts.last()
diff --git a/vlib/v/checker/tests/none_match_cond_err.out b/vlib/v/checker/tests/none_match_cond_err.out
new file mode 100644
index 00000000000000..9853c66e45a44b
--- /dev/null
+++ b/vlib/v/checker/tests/none_match_cond_err.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/none_match_cond_err.vv:1:1: error: `none` cannot be a match condition
+    1 | match none {
+      | ~~~~~~~~~~~~
+    2 |     none {}
+    3 |     else {}
diff --git a/vlib/v/checker/tests/none_match_cond_err.vv b/vlib/v/checker/tests/none_match_cond_err.vv
new file mode 100644
index 00000000000000..85ad2b7ec7cae7
--- /dev/null
+++ b/vlib/v/checker/tests/none_match_cond_err.vv
@@ -0,0 +1,4 @@
+match none {
+	none {}
+	else {}
+}