From 570a12da8df8481184e0c631f2d5a851c51c4a13 Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Sat, 26 Aug 2023 03:50:53 +0800
Subject: [PATCH] cgen: fix generic struct with option fn field (#19218)

---
 vlib/v/gen/c/cgen.v                                |  2 +-
 vlib/v/tests/generics_struct_with_option_fn_test.v | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/generics_struct_with_option_fn_test.v

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index b558e8f0b23f8b..59ceb54dbea487 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -3603,7 +3603,7 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 	if node.or_block.kind != .absent && !g.is_assign_lhs && g.table.sym(node.typ).kind != .chan {
 		is_ptr := sym.kind in [.interface_, .sum_type]
 		stmt_str := g.go_before_stmt(0).trim_space()
-		styp := g.typ(node.typ)
+		styp := g.typ(g.unwrap_generic(node.typ))
 		g.empty_line = true
 		tmp_var := g.new_tmp_var()
 		g.write('${styp} ${tmp_var} = ')
diff --git a/vlib/v/tests/generics_struct_with_option_fn_test.v b/vlib/v/tests/generics_struct_with_option_fn_test.v
new file mode 100644
index 00000000000000..b3ba7d053b28a9
--- /dev/null
+++ b/vlib/v/tests/generics_struct_with_option_fn_test.v
@@ -0,0 +1,14 @@
+struct Cmp[K] {
+	cmp ?fn (K, K) bool
+}
+
+fn (c Cmp[K]) compare(a K, b K) bool {
+	cmp := c.cmp or { return a < b }
+	return cmp(a, b)
+}
+
+fn test_generic_struct_with_option_fn() {
+	c := Cmp[int]{}
+	print(c.compare(1, 2))
+	assert c.compare(1, 2)
+}