Function wasmtime_structref_set_field 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn wasmtime_structref_set_field(
    cx: WasmtimeStoreContextMut<'_>,
    structref: Option<&wasmtime_structref_t>,
    index: usize,
    val: &wasmtime_val_t,
) -> Option<Box<wasmtime_error_t>>