Function sourceview5_sys::gtk_source_completion_provider_populate_async

pub unsafe extern "C" fn gtk_source_completion_provider_populate_async(
    self_: *mut GtkSourceCompletionProvider, 
    context: *mut GtkSourceCompletionContext, 
    cancellable: *mut GCancellable, 
    callback: GAsyncReadyCallback, 
    user_data: gpointer
)

This is supported on crate feature v5_0 only.