From 3ef219a7c65b2025588929c6407bd5832aebccfd Mon Sep 17 00:00:00 2001
From: Felix Ehlers <fleximus@users.noreply.github.com>
Date: Thu, 1 Jan 2026 09:29:30 +0100
Subject: [PATCH] checker: error for unwrapped option/result types used with in
 operator (fix #26208) (#26223)

---
 vlib/v/checker/infix.v                        | 17 ++++----------
 .../checker/tests/option_in_operator_err.out  | 13 +++++++++++
 .../v/checker/tests/option_in_operator_err.vv | 23 +++++++++++++++++++
 ...wrapped_option_result_in_operation_err.out |  8 +++----
 4 files changed, 45 insertions(+), 16 deletions(-)
 create mode 100644 vlib/v/checker/tests/option_in_operator_err.out
 create mode 100644 vlib/v/checker/tests/option_in_operator_err.vv

diff --git a/vlib/v/checker/infix.v b/vlib/v/checker/infix.v
index 462f226d9..4a2e33711 100644
--- a/vlib/v/checker/infix.v
+++ b/vlib/v/checker/infix.v
@@ -255,6 +255,11 @@ fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 			}
 		}
 		.key_in, .not_in {
+			if left_type.has_flag(.option) || left_type.has_flag(.result) {
+				option_or_result := if left_type.has_flag(.option) { 'Option' } else { 'Result' }
+				c.error('unwrapped ${option_or_result} cannot be used with `${node.op.str()}`',
+					left_pos)
+			}
 			match right_final_sym.kind {
 				.array {
 					if left_sym.kind !in [.sum_type, .interface] {
@@ -315,18 +320,6 @@ fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 					}
 				}
 			}
-			if mut node.left is ast.CallExpr {
-				if node.left.return_type.has_flag(.option)
-					|| node.left.return_type.has_flag(.result) {
-					option_or_result := if node.left.return_type.has_flag(.option) {
-						'option'
-					} else {
-						'result'
-					}
-					c.error('unwrapped ${option_or_result} cannot be used with `${node.op.str()}`',
-						left_pos)
-				}
-			}
 			node.promoted_type = ast.bool_type
 			return ast.bool_type
 		}
diff --git a/vlib/v/checker/tests/option_in_operator_err.out b/vlib/v/checker/tests/option_in_operator_err.out
new file mode 100644
index 000000000..a69c08722
--- /dev/null
+++ b/vlib/v/checker/tests/option_in_operator_err.out
@@ -0,0 +1,13 @@
+vlib/v/checker/tests/option_in_operator_err.vv:19:11: error: unwrapped Option cannot be used with `in`
+   17 | 
+   18 |     // Optional struct field with map
+   19 |     _ = item.owner_id in m
+      |              ~~~~~~~~
+   20 | 
+   21 |     // Optional function return with array
+vlib/v/checker/tests/option_in_operator_err.vv:22:6: error: unwrapped Option cannot be used with `in`
+   20 | 
+   21 |     // Optional function return with array
+   22 |     _ = get_opt() in arr
+      |         ~~~~~~~~~
+   23 | }
diff --git a/vlib/v/checker/tests/option_in_operator_err.vv b/vlib/v/checker/tests/option_in_operator_err.vv
new file mode 100644
index 000000000..752f72960
--- /dev/null
+++ b/vlib/v/checker/tests/option_in_operator_err.vv
@@ -0,0 +1,23 @@
+struct Item {
+	owner_id ?string
+}
+
+fn get_opt() ?int {
+	return 1
+}
+
+fn main() {
+	item := Item{
+		owner_id: 'key'
+	}
+	arr := [1, 2, 3]
+	m := {
+		'key': 1
+	}
+
+	// Optional struct field with map
+	_ = item.owner_id in m
+
+	// Optional function return with array
+	_ = get_opt() in arr
+}
diff --git a/vlib/v/checker/tests/unwrapped_option_result_in_operation_err.out b/vlib/v/checker/tests/unwrapped_option_result_in_operation_err.out
index 6b2e8d7a5..0708c848e 100644
--- a/vlib/v/checker/tests/unwrapped_option_result_in_operation_err.out
+++ b/vlib/v/checker/tests/unwrapped_option_result_in_operation_err.out
@@ -1,25 +1,25 @@
-vlib/v/checker/tests/unwrapped_option_result_in_operation_err.vv:3:6: error: unwrapped result cannot be used with `!in`
+vlib/v/checker/tests/unwrapped_option_result_in_operation_err.vv:3:6: error: unwrapped Result cannot be used with `!in`
     1 | fn main() {
     2 |     list := ['string']
     3 |     _ = return_string_or_error() !in list
       |         ~~~~~~~~~~~~~~~~~~~~~~~~
     4 |     _ = return_string_or_error() in list
     5 |     _ = return_string_or_none() in list
-vlib/v/checker/tests/unwrapped_option_result_in_operation_err.vv:4:6: error: unwrapped result cannot be used with `in`
+vlib/v/checker/tests/unwrapped_option_result_in_operation_err.vv:4:6: error: unwrapped Result cannot be used with `in`
     2 |     list := ['string']
     3 |     _ = return_string_or_error() !in list
     4 |     _ = return_string_or_error() in list
       |         ~~~~~~~~~~~~~~~~~~~~~~~~
     5 |     _ = return_string_or_none() in list
     6 |     _ = return_string_or_error() !in list
-vlib/v/checker/tests/unwrapped_option_result_in_operation_err.vv:5:6: error: unwrapped option cannot be used with `in`
+vlib/v/checker/tests/unwrapped_option_result_in_operation_err.vv:5:6: error: unwrapped Option cannot be used with `in`
     3 |     _ = return_string_or_error() !in list
     4 |     _ = return_string_or_error() in list
     5 |     _ = return_string_or_none() in list
       |         ~~~~~~~~~~~~~~~~~~~~~~~
     6 |     _ = return_string_or_error() !in list
     7 | }
-vlib/v/checker/tests/unwrapped_option_result_in_operation_err.vv:6:6: error: unwrapped result cannot be used with `!in`
+vlib/v/checker/tests/unwrapped_option_result_in_operation_err.vv:6:6: error: unwrapped Result cannot be used with `!in`
     4 |     _ = return_string_or_error() in list
     5 |     _ = return_string_or_none() in list
     6 |     _ = return_string_or_error() !in list
-- 
2.39.5