From 895af3e45c827b7586dd71bda561eea47acf8b40 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 21 Apr 2026 16:55:17 +0300
Subject: [PATCH] checker: fix ice when sorting an array of functions (fixes
 #10739)

---
 vlib/v/checker/infix.v                                | 10 ++++++++++
 vlib/v/checker/tests/array_sort_function_type_err.out |  6 ++++++
 vlib/v/checker/tests/array_sort_function_type_err.vv  |  8 ++++++++
 3 files changed, 24 insertions(+)
 create mode 100644 vlib/v/checker/tests/array_sort_function_type_err.out
 create mode 100644 vlib/v/checker/tests/array_sort_function_type_err.vv

diff --git a/vlib/v/checker/infix.v b/vlib/v/checker/infix.v
index a9709b9b9..d9b6441e2 100644
--- a/vlib/v/checker/infix.v
+++ b/vlib/v/checker/infix.v
@@ -728,6 +728,16 @@ fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 			}
 			if left_sym.kind in [.array, .array_fixed] && right_sym.kind in [.array, .array_fixed] {
 				c.error('only `==` and `!=` are defined on arrays', node.pos)
+			} else if left_sym.kind == .function || right_sym.kind == .function {
+				left_name := c.table.type_to_str(unwrapped_left_type)
+				right_name := c.table.type_to_str(unwrapped_right_type)
+				if left_sym.kind == .function && right_sym.kind == .function
+					&& left_name == right_name {
+					c.error('undefined operation `${left_name}` ${node.op.str()} `${right_name}`',
+						left_right_pos)
+				} else {
+					c.error('mismatched types `${left_name}` and `${right_name}`', left_right_pos)
+				}
 			} else if left_sym.info is ast.Struct && left_sym.info.generic_types.len > 0 {
 				node.promoted_type = ast.bool_type
 				return ast.bool_type
diff --git a/vlib/v/checker/tests/array_sort_function_type_err.out b/vlib/v/checker/tests/array_sort_function_type_err.out
new file mode 100644
index 000000000..625ca5153
--- /dev/null
+++ b/vlib/v/checker/tests/array_sort_function_type_err.out
@@ -0,0 +1,6 @@
+vlib/v/checker/tests/array_sort_function_type_err.vv:7:9: error: undefined operation `&fn ()` > `&fn ()`
+    5 | fn main() {
+    6 |     mut x := [main, b, c]
+    7 |     x.sort(a > b)
+      |            ~~~~~
+    8 | }
diff --git a/vlib/v/checker/tests/array_sort_function_type_err.vv b/vlib/v/checker/tests/array_sort_function_type_err.vv
new file mode 100644
index 000000000..9fb133e78
--- /dev/null
+++ b/vlib/v/checker/tests/array_sort_function_type_err.vv
@@ -0,0 +1,8 @@
+fn b() {}
+
+fn c() {}
+
+fn main() {
+	mut x := [main, b, c]
+	x.sort(a > b)
+}
-- 
2.39.5