From 2f2efb73397af9d7cd757c09bac2de8c1e591699 Mon Sep 17 00:00:00 2001
From: kbkpbot <kbkpbot@sina.com>
Date: Tue, 18 Nov 2025 00:18:15 +0800
Subject: [PATCH] parser: allow using `a`, `b` and `it` as var names, when
 using the builtin array methods (fix #25729) (#25755)

---
 vlib/v/parser/assign.v                  |  5 ++++
 vlib/v/tests/skip_sort_arg_check_test.v | 38 +++++++++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 vlib/v/tests/skip_sort_arg_check_test.v

diff --git a/vlib/v/parser/assign.v b/vlib/v/parser/assign.v
index 64a954775..06fc68be8 100644
--- a/vlib/v/parser/assign.v
+++ b/vlib/v/parser/assign.v
@@ -49,6 +49,11 @@ fn (mut p Parser) check_undefined_variables(names []string, val ast.Expr) ! {
 		}
 		ast.CallExpr {
 			p.check_undefined_variables(names, val.left)!
+			// arr.sort(a < b) , arr.sorted(a < b), it := [2,3,4].map(it*2), it := [2,3,4].filter(it % 2 == 0), etc.
+			if val.args.len == 1
+				&& val.name in ['sort', 'sorted', 'map', 'filter', 'any', 'all', 'count'] {
+				return
+			}
 			for arg in val.args {
 				p.check_undefined_variables(names, arg.expr)!
 			}
diff --git a/vlib/v/tests/skip_sort_arg_check_test.v b/vlib/v/tests/skip_sort_arg_check_test.v
new file mode 100644
index 000000000..b7719028d
--- /dev/null
+++ b/vlib/v/tests/skip_sort_arg_check_test.v
@@ -0,0 +1,38 @@
+// should allow `a:=arr.sorted(a < b)` use `a` as var name
+fn test_skip_check_sort_arg_a_b() {
+	arr := [4, 2, 1, 3]
+	a := arr.sorted(a < b)
+	assert a == [1, 2, 3, 4]
+	b := arr.sorted(a > b)
+	assert b == [4, 3, 2, 1]
+}
+
+// should allow `it:=arr.map(it*2)` use `it` as var name
+fn test_skip_check_map_arg_it() {
+	it := [4, 2, 1, 3].map(it * 2)
+	assert it == [8, 4, 2, 6]
+}
+
+// should allow `it:=arr.filter(it%2==0)` use `it` as var name
+fn test_skip_check_filter_arg_it() {
+	it := [4, 2, 1, 3].filter(it % 2 == 0)
+	assert it == [4, 2]
+}
+
+// should allow `it:=arr.any(it%2==0)` use `it` as var name
+fn test_skip_check_any_arg_it() {
+	it := [4, 2, 1, 3].any(it % 2 == 0)
+	assert it
+}
+
+// should allow `it:=arr.all(it%2==0)` use `it` as var name
+fn test_skip_check_all_arg_it() {
+	it := [4, 2, 1, 3].all(it % 2 == 0)
+	assert !it
+}
+
+// should allow `it:=arr.count(it%2==0)` use `it` as var name
+fn test_skip_check_count_arg_it() {
+	it := [4, 2, 1, 3].count(it % 2 == 0)
+	assert it == 2
+}
-- 
2.39.5