From 5adfc55b82c822142089aae0afb9c27c8ec4a082 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Mon, 5 May 2025 02:41:00 -0300
Subject: [PATCH] cgen: fix codegen for anon option fn struct field init (fix
 #24392) (#24400)

---
 vlib/v/gen/c/cgen.v                           |  5 ++
 vlib/v/gen/c/struct.v                         | 11 +++--
 .../options/option_fn_struct_init_test.v      | 47 +++++++++++++++++++
 3 files changed, 59 insertions(+), 4 deletions(-)
 create mode 100644 vlib/v/tests/options/option_fn_struct_init_test.v

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 65f376af9..0638fb2b3 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -2295,6 +2295,7 @@ fn (mut g Gen) expr_with_tmp_var(expr ast.Expr, expr_typ ast.Type, ret_typ ast.T
 			g.writeln('${g.styp(ret_typ)} ${tmp_var};')
 		}
 		mut expr_is_fixed_array_var := false
+		mut fn_option_clone := false
 		if ret_typ_is_option {
 			if expr_typ_is_option && expr in [ast.StructInit, ast.ArrayInit, ast.MapInit] {
 				simple_assign = expr is ast.StructInit
@@ -2328,6 +2329,7 @@ fn (mut g Gen) expr_with_tmp_var(expr ast.Expr, expr_typ ast.Type, ret_typ ast.T
 							g.write('(')
 							g.write_fn_ptr_decl(&final_ret_sym.info, '')
 							g.write(')')
+							fn_option_clone = expr is ast.SelectorExpr && expr_typ.has_flag(.option)
 						}
 					}
 				}
@@ -2339,6 +2341,9 @@ fn (mut g Gen) expr_with_tmp_var(expr ast.Expr, expr_typ ast.Type, ret_typ ast.T
 			g.write('_result_ok(&(${styp}[]) { ')
 		}
 		g.expr_with_cast(expr, expr_typ, ret_typ)
+		if fn_option_clone {
+			g.write('.data')
+		}
 		if ret_typ_is_option {
 			if simple_assign {
 				g.writeln(';')
diff --git a/vlib/v/gen/c/struct.v b/vlib/v/gen/c/struct.v
index e8081664c..b51dfd2e4 100644
--- a/vlib/v/gen/c/struct.v
+++ b/vlib/v/gen/c/struct.v
@@ -742,21 +742,21 @@ fn (mut g Gen) struct_init_field(sfield ast.StructInitField, language ast.Langua
 						g.fixed_array_var_init(tmp_var, false, field_unwrap_sym.info.elem_type,
 							field_unwrap_sym.info.size)
 					} else {
-						g.struct_init_field_default(field_unwrap_typ, sfield)
+						g.struct_init_field_default(field_unwrap_typ, sfield, field_unwrap_sym)
 					}
 				}
 				else {
-					g.struct_init_field_default(field_unwrap_typ, sfield)
+					g.struct_init_field_default(field_unwrap_typ, sfield, field_unwrap_sym)
 				}
 			}
 		} else {
-			g.struct_init_field_default(field_unwrap_typ, sfield)
+			g.struct_init_field_default(field_unwrap_typ, sfield, field_unwrap_sym)
 		}
 		g.inside_cast_in_heap = inside_cast_in_heap // restore value for further struct inits
 	}
 }
 
-fn (mut g Gen) struct_init_field_default(field_unwrap_typ ast.Type, sfield &ast.StructInitField) {
+fn (mut g Gen) struct_init_field_default(field_unwrap_typ ast.Type, sfield &ast.StructInitField, field_unwrap_sym ast.TypeSymbol) {
 	if field_unwrap_typ != ast.voidptr_type && field_unwrap_typ != ast.nil_type
 		&& (sfield.expected_type.is_ptr() && !sfield.expected_type.has_flag(.shared_f))
 		&& !sfield.expected_type.has_flag(.option) && !field_unwrap_typ.is_any_kind_of_pointer()
@@ -769,6 +769,9 @@ fn (mut g Gen) struct_init_field_default(field_unwrap_typ ast.Type, sfield &ast.
 		g.expr_with_opt(sfield.expr, field_unwrap_typ, sfield.expected_type)
 	} else if sfield.expr is ast.LambdaExpr && sfield.expected_type.has_flag(.option) {
 		g.expr_opt_with_cast(sfield.expr, field_unwrap_typ, sfield.expected_type)
+	} else if field_unwrap_sym.kind == .function && sfield.expected_type.has_flag(.option) {
+		tmp_out_var := g.new_tmp_var()
+		g.expr_with_tmp_var(sfield.expr, field_unwrap_typ, sfield.expected_type, tmp_out_var)
 	} else {
 		g.left_is_opt = true
 		g.expr_with_cast(sfield.expr, field_unwrap_typ, sfield.expected_type)
diff --git a/vlib/v/tests/options/option_fn_struct_init_test.v b/vlib/v/tests/options/option_fn_struct_init_test.v
new file mode 100644
index 000000000..55613c898
--- /dev/null
+++ b/vlib/v/tests/options/option_fn_struct_init_test.v
@@ -0,0 +1,47 @@
+type Baz = Foo
+
+@[heap]
+struct Foo {
+	a  int    = 123
+	b  string = 'b'
+	cb ?fn (&Foo)
+}
+
+@[heap]
+struct Bar {
+	a  int    = 321
+	b  string = 'a'
+	cb ?fn (&Baz)
+}
+
+fn g(a Foo) Foo {
+	return a
+}
+
+fn t(a Bar) Foo {
+	return g(a: 123, b: 'foo', cb: a.cb)
+}
+
+fn test_main() {
+	a := Foo{
+		cb: none
+	}
+
+	b := Foo{
+		cb: fn (a &Foo) {
+		}
+	}
+
+	w := Bar{
+		cb: b.cb
+	}
+
+	z := Bar{
+		cb: a.cb
+	}
+
+	t(a: 1, cb: a.cb)
+	t(a: 2, cb: b.cb)
+	t(a: 3, cb: w.cb)
+	t(a: 4, cb: z.cb)
+}
-- 
2.39.5