From 84152cc709fe2b293a885cd5a4cebde7f599d1fd Mon Sep 17 00:00:00 2001
From: CreeperFace <165158232+dy-tea@users.noreply.github.com>
Date: Wed, 22 Oct 2025 12:36:41 +0100
Subject: [PATCH] checker: prevent array.insert for array of references when
 non-reference is passed (fix #25511) (#25557)

---
 vlib/v/checker/fn.v                            | 11 +++++++++--
 .../tests/array_of_refs_insert_non_ref.out     | 13 +++++++++++++
 .../tests/array_of_refs_insert_non_ref.vv      | 18 ++++++++++++++++++
 3 files changed, 40 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/checker/tests/array_of_refs_insert_non_ref.out
 create mode 100644 vlib/v/checker/tests/array_of_refs_insert_non_ref.vv

diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index 75a06a83b..d6aafa788 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -3321,8 +3321,15 @@ fn (mut c Checker) array_builtin_method_call(mut node ast.CallExpr, left_type as
 				node.args[i].typ = c.expr(mut arg.expr)
 				if i == val_arg_n {
 					arg_sym := c.table.sym(node.args[i].typ)
-					if !c.check_types(node.args[i].typ, info.elem_type)
-						&& !c.check_types(left_type, node.args[i].typ) {
+					base_arg_type := c.unwrap_generic(node.args[i].typ)
+					if c.check_types(base_arg_type, info.elem_type) {
+						if !base_arg_type.is_ptr() && info.elem_type.is_ptr()
+							&& info.elem_type.share() == .mut_t {
+							c.error('cannot ${method_name} `${arg_sym.name}` to `${left_sym.name}`',
+								arg.expr.pos())
+							continue
+						}
+					} else if !c.check_types(base_arg_type, c.unwrap_generic(left_type)) {
 						c.error('cannot ${method_name} `${arg_sym.name}` to `${left_sym.name}`',
 							arg.expr.pos())
 						continue
diff --git a/vlib/v/checker/tests/array_of_refs_insert_non_ref.out b/vlib/v/checker/tests/array_of_refs_insert_non_ref.out
new file mode 100644
index 000000000..bb18dbfdc
--- /dev/null
+++ b/vlib/v/checker/tests/array_of_refs_insert_non_ref.out
@@ -0,0 +1,13 @@
+vlib/v/checker/tests/array_of_refs_insert_non_ref.vv:16:12: error: cannot append `Dummy` to `[]&Dummy`
+   14 |         v: 1
+   15 |     }
+   16 |     c.vals << d
+      |               ^
+   17 |     c.vals.insert(0, d)
+   18 | }
+vlib/v/checker/tests/array_of_refs_insert_non_ref.vv:17:19: error: cannot insert `Dummy` to `[]&Dummy`
+   15 |     }
+   16 |     c.vals << d
+   17 |     c.vals.insert(0, d)
+      |                      ^
+   18 | }
diff --git a/vlib/v/checker/tests/array_of_refs_insert_non_ref.vv b/vlib/v/checker/tests/array_of_refs_insert_non_ref.vv
new file mode 100644
index 000000000..04db93008
--- /dev/null
+++ b/vlib/v/checker/tests/array_of_refs_insert_non_ref.vv
@@ -0,0 +1,18 @@
+struct Dummy {
+	v int
+}
+
+@[heap]
+struct Container {
+mut:
+	vals []&Dummy
+}
+
+fn main() {
+	mut c := &Container{}
+	d := Dummy{
+		v: 1
+	}
+	c.vals << d
+	c.vals.insert(0, d)
+}
-- 
2.39.5