error:  #119: cast to type "struct led_class" is not allowed
      struct led_class* self = (struct led_class) malloc(sizeof(led_class));

typedef struct led_class
{
    uint8_t pin;
    GPIO_TypeDef* gpio;
} led_class;

struct led_class* led_create(GPIO_TypeDef* GPIO, uint8_t pin)
{
    struct led_class* self = (struct led_class) malloc(sizeof(led_class));
    self->gpio = GPIO;
    self->pin = pin;
    led_init(self);
    return self;
}

void led_init(led_class* self)
{
    self->gpio->MODER |= 1 << (self->pin * 2);
    self->gpio->ODR = 0 << self->pin;
}

void led_on(led_class* self)
{
    self->gpio->ODR = 1 << self->pin;
}

int main(void)
{
    led_class* led = led_create(GPIOD, 2);
    led_on(led);
}

struct led_class* led_create(GPIO_TypeDef* GPIO, uint8_t pin)
{
    led_class* self = malloc(sizeof(led_class));
    self->gpio = GPIO;
    self->pin = pin;
    led_init(self);
    return self;
}