cgen: fix struct field init with fixed array using index (fix #22616) (#22641)

Author: yuyi98

vlib/v/gen/c/struct.v

@@ -673,7 +673,8 @@ fn (mut g Gen) struct_init_field(sfield ast.StructInitField, language ast.Langua
 			info := field_unwrap_sym.info as ast.ArrayFixed
 			g.fixed_array_var_init(g.expr_string(sfield.expr), sfield.expr.is_auto_deref_var(),
 				info.elem_type, info.size)
-		} else if field_unwrap_sym.kind == .array_fixed && sfield.expr is ast.CallExpr {
+		} else if field_unwrap_sym.kind == .array_fixed && (sfield.expr is ast.CallExpr
+			|| (sfield.expr is ast.ArrayInit && sfield.expr.has_index)) {
 			info := field_unwrap_sym.info as ast.ArrayFixed
 			tmp_var := g.expr_with_var(sfield.expr, sfield.typ, sfield.expected_type)
 			g.fixed_array_var_init(tmp_var, false, info.elem_type, info.size)

vlib/v/tests/structs/struct_field_init_with_fixed_array_init_test.v

@@ -0,0 +1,18 @@
+fn test_struct_field_init_with_fixed_array_init() {
+	mut a := [5]int{init: [1, 2][index] or { 0 }}
+	struct ArrayTest {
+		aa [5]int
+	}
+
+	array_a := ArrayTest{
+		aa: a
+	}
+	println('array_a: ${array_a}')
+	assert array_a.aa == [1, 2, 0, 0, 0]!
+
+	array_b := ArrayTest{
+		aa: [5]int{init: [1, 2][index] or { 0 }}
+	}
+	println('array_b: ${array_b}')
+	assert array_b.aa == [1, 2, 0, 0, 0]!
+}