From df118aa448aa72279d4872931492b73395186e94 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 11 Mar 2026 16:31:04 +0300
Subject: [PATCH] cgen: builder error (fixes #14819)

---
 vlib/v/gen/c/cgen.v                           |  8 ++---
 .../generic_callback_assignment.c.must_have   |  4 +++
 .../c/testdata/generic_callback_assignment.vv | 32 +++++++++++++++++++
 3 files changed, 39 insertions(+), 5 deletions(-)
 create mode 100644 vlib/v/gen/c/testdata/generic_callback_assignment.c.must_have
 create mode 100644 vlib/v/gen/c/testdata/generic_callback_assignment.vv

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 818a8b907..2ce1de989 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -3498,11 +3498,9 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type_raw ast.Type, expected_typ
 			g.write('*')
 		}
 	}
-	if (exp_sym.kind == .function && !expected_type.has_option_or_result())
-		|| (g.inside_struct_init && expected_type == ast.voidptr_type
-		&& expected_type != got_type_raw && expr !is ast.StructInit)
-		|| (g.inside_call && expected_type == ast.voidptr_type && expr is ast.ArrayInit
-		&& (expr as ast.ArrayInit).is_fixed) {
+	if (g.inside_struct_init && expected_type == ast.voidptr_type && expected_type != got_type_raw
+		&& expr !is ast.StructInit) || (g.inside_call && expected_type == ast.voidptr_type
+		&& expr is ast.ArrayInit && (expr as ast.ArrayInit).is_fixed) {
 		g.write('(voidptr)')
 	}
 	// no cast
diff --git a/vlib/v/gen/c/testdata/generic_callback_assignment.c.must_have b/vlib/v/gen/c/testdata/generic_callback_assignment.c.must_have
new file mode 100644
index 000000000..7d2a63a3f
--- /dev/null
+++ b/vlib/v/gen/c/testdata/generic_callback_assignment.c.must_have
@@ -0,0 +1,4 @@
+main__Client_on_T_main__Ready(client, _S("ready"), main__on_ready);
+main__Client_on_T_main__Message(client, _S("message_create"), main__on_message);
+client->ready_callback = handler;
+client->message_callback = handler;
diff --git a/vlib/v/gen/c/testdata/generic_callback_assignment.vv b/vlib/v/gen/c/testdata/generic_callback_assignment.vv
new file mode 100644
index 000000000..95973cdf3
--- /dev/null
+++ b/vlib/v/gen/c/testdata/generic_callback_assignment.vv
@@ -0,0 +1,32 @@
+@[heap]
+struct Client {
+mut:
+	ready_callback   ReadyHandler   = unsafe { nil }
+	message_callback MessageHandler = unsafe { nil }
+}
+
+struct Ready {}
+
+struct Message {}
+
+type ReadyHandler = fn (mut c Client, msg &Ready)
+
+type MessageHandler = fn (mut c Client, msg &Message)
+
+fn (mut client Client) on[T](event string, handler fn (mut c Client, msg &T)) {
+	if event == 'ready' {
+		client.ready_callback = handler
+	} else if event == 'message_create' {
+		client.message_callback = handler
+	}
+}
+
+fn on_ready(mut _client Client, _message &Ready) {}
+
+fn on_message(mut _client Client, _message &Message) {}
+
+fn main() {
+	mut client := &Client{}
+	client.on[Ready]('ready', on_ready)
+	client.on[Message]('message_create', on_message)
+}
-- 
2.39.5