cgen: fix default init value for an array of option (#17538)

vlib/v/gen/c/array.v

@@ -343,10 +343,18 @@ fn (mut g Gen) array_init_with_fields(node ast.ArrayInit, elem_type Type, is_amp
 		g.writeln('; ${ind}++) {')
 		g.write('\t${tmp}[${ind}] = ')
 		if node.has_default {
+			if node.elem_type.has_flag(.option) {
+				g.expr_with_opt(node.default_expr, node.default_type, node.elem_type)
+			} else {
 				g.expr_with_cast(node.default_expr, node.default_type, node.elem_type)
+			}
+		} else {
+			if node.elem_type.has_flag(.option) {
+				g.expr_with_opt(ast.None{}, ast.none_type, node.elem_type)
 			} else {
 				g.write(g.type_default(node.elem_type))
 			}
+		}
 		g.writeln(';')
 		g.writeln('}')
 		g.write(line)
@@ -355,6 +363,10 @@ fn (mut g Gen) array_init_with_fields(node ast.ArrayInit, elem_type Type, is_amp
 		g.write('&(${elem_styp}[]){')
 		g.expr_with_cast(node.default_expr, node.default_type, node.elem_type)
 		g.write('})')
+	} else if node.has_len && node.elem_type.has_flag(.option) {
+		g.write('&')
+		g.expr_with_opt(ast.None{}, ast.none_type, node.elem_type)
+		g.write(')')
 	} else if node.has_len && node.elem_type == ast.string_type {
 		g.write('&(${elem_styp}[]){')
 		g.write('_SLIT("")')

vlib/v/tests/check_init_value_for_arrays_of_option_test.v

@@ -0,0 +1,59 @@
+fn check_init_value_for_arrays_of_option[T]() {
+	a := []?T{len: 2}
+	assert a.len == 2
+	for value in a {
+		assert value == none
+		println(value)
+	}
+}
+
+enum MyEnum {
+	zero
+	one
+	two
+}
+
+enum MyEnum32 as u32 {
+	zero
+	one
+	two
+}
+
+struct MyStruct {
+	x    int    = 123
+	name string = 'abc'
+}
+
+fn test_primitives() {
+	check_init_value_for_arrays_of_option[i8]()
+	check_init_value_for_arrays_of_option[i16]()
+	check_init_value_for_arrays_of_option[i32]()
+	check_init_value_for_arrays_of_option[int]()
+	check_init_value_for_arrays_of_option[i64]()
+
+	check_init_value_for_arrays_of_option[u8]()
+	check_init_value_for_arrays_of_option[byte]()
+	check_init_value_for_arrays_of_option[u16]()
+	check_init_value_for_arrays_of_option[u32]()
+	check_init_value_for_arrays_of_option[u64]()
+
+	check_init_value_for_arrays_of_option[f32]()
+	check_init_value_for_arrays_of_option[f64]()
+
+	check_init_value_for_arrays_of_option[string]()
+	check_init_value_for_arrays_of_option[rune]()
+}
+
+fn test_arrays() {
+	check_init_value_for_arrays_of_option[[]int]()
+	check_init_value_for_arrays_of_option[[]f32]()
+}
+
+fn test_enums() {
+	check_init_value_for_arrays_of_option[MyEnum]()
+	check_init_value_for_arrays_of_option[MyEnum32]()
+}
+
+fn test_structs() {
+	check_init_value_for_arrays_of_option[MyStruct]()
+}