在 Rust 中将其作为函数参数传递时如何为 futures_intrusive::sync::GenericSemaphore 指定类型

Question

I am trying to implement a shared semaphore using futures_intrusive::sync::GenericSemaphore . The code looks like this:

use std::path::Path;
use std::fmt::Write;

use futures_intrusive::sync::GenericSemaphore;


mod linear_bathtubbing

async fn refresh_file(raster_file: &Path, slr: f64, output_path: &Path, chunk_size: u32, semaphore: &GenericSemaphore) {

    if output_path.exists().not() {
        build_required_windows(&raster_file, slr, chunk_size, output_path, &semaphore).await?;
    }
}

#[tokio::main]
async fn main() {
    let semaphore = GenericSemaphore::new(false, 100);
    for raster_data in RASTER_INPUTS.iter() {
        let [state, raster_file, chunk_size] = raster_data;
        let chunk_size: u32 = chunk_size.parse().unwrap();
        let raster_filename: Vec<&str> = raster_file.split("/").collect();
        for slr_level in SLR_LEVELS.iter() {
            let mut output_filename = String::from("slr_dems/linear/");
            output_filename += state;
            output_filename += "/slr";
            write!(output_filename, "{:1.1}", slr_level).unwrap();
            write!(output_filename, "_{}", raster_filename[raster_filename.len() -1]).unwrap();
            linear_bathtubbing::refresh_file(Path::new(&raster_file), *slr_level, Path::new(&output_filename), chunk_size, &semaphore).await?;
        };
    }
}

However I get an error:

error[E0107]: missing generics for struct `GenericSemaphore`
   --> src/linear_bathtubbing.rs:129:106
    |
129 | pub async fn refresh_file(raster_file: &Path, slr: f64, output_path: &Path, chunk_size: u32, semaphore: &GenericSemaphore) {
    |                                                                                                          ^^^^^^^^^^^^^^^^ expected 1 generic argument
    |
note: struct defined here, with 1 generic parameter: `MutexType`
   --> /.../.cargo/registry/src/github.com-1ecc6299db9ec823/futures-intrusive-0.4.0/src/sync/semaphore.rs:433:12
    |
433 | pub struct GenericSemaphore<MutexType: RawMutex> {
    |            ^^^^^^^^^^^^^^^^ ---------
help: add missing generic argument
    |
129 | pub async fn refresh_file(raster_file: &Path, slr: f64, output_path: &Path, chunk_size: u32, semaphore: &GenericSemaphore<MutexType>) {
    |                                                                                                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~

For more information about this error, try `rustc --explain E0107`.

It seems like I need to add missing generic argument , but I am not sure how to proceed. I have tried specifying a Mutex type and other things without success, but I think this probably has a straightforward answer which I simply don't know because of lack of experience with Rust.

Answer 1

You just need to add the generic type parameter that GenericSemaphore expects to the function signature.

async fn refresh_file<T: RawMutex>(
    raster_file: &Path,
    slr: f64,
    output_path: &Path,
    chunk_size: u32,
    semaphore: &GenericSemaphore<T>
) {

Alternatively, using impl syntax (which is sugar for the code above):

async fn refresh_file(
    raster_file: &Path,
    slr: f64,
    output_path: &Path,
    chunk_size: u32,
    semaphore: &GenericSemaphore<impl RawMutex>
) {