Editing and saving data dependency (like `include_bytes!`) doesn't trigger `cargo check`

[Vlad-Shcherbina]

To reproduce

1. cargo init --bin
2. Open this project in VSCode.
3. Create the file data in the root of the project, with the following contents:

   hello
   

   (no trailing newline)
4. Ctrl-S
5. Put the following in src/main.rs:

   trait MyTrait {}
   
   impl MyTrait for [u8; 5] {}
   
   fn main() {
       let _t: &dyn MyTrait = include_bytes!("../data");
   }

6. Ctrl-S, observe that rust-analyzer shows no errors.
7. Go back to the file data and edit it, changing its length.
8. Ctrl-S, observe that rust-analyzer shows no errors.
9. Go back to file src/main.rs.
10. Ctrl-S, observe that rust-analyzer shows an error belatedly ("the trait bound [u8; 6]: MyTrait is not satisfied").

In the perfect world, the error would be displayed on step 8, immediately after editing and saving the data file.

This is an artificial minimal example.
For a motivating real-world example, consider a compile-time templating system like Askama. Askama uses derive proc macro to process template files, and emits include_bytes!() as a way to let the build system know about the data dependency. Mistakes in the template can result in compile errors. It would be nice if such errors were reported immediately on save, without having to manually trigger cargo check.

Version info

rust-analyzer version: 0.4.1296-standalone (2656297 2022-11-20)
VSCode version: 1.71.1
cargo 1.66.0-nightly (73ba3f35e 2022-09-18)
rustc 1.66.0-nightly (3f83906 2022-09-24)

[bjorn3]

Rust-analyzer only watches for files with the .rs extension and for Cargo.toml and Cargo.lock. Watching for more files would likely require parsing the .d files emitted by cargo as otherwise we did have to trigger cargo check when any file is changed, even if completely unrelated.