RA shows warnings in autogenerated files inside target directory when using alternative target location

rust-analyzer version: 0.0.0 (cc0bb71e2 2022-07-02)

rustc version: rustc 1.64.0-nightly (46b8c23f3 2022-07-01)

relevant settings:

{
    "rust-analyzer.server.extraEnv": {
        "CARGO_TARGET_DIR": "target-ra"
    },
    "rust-analyzer.checkOnSave.command": "clippy"
}

I use target-ra as a separate target directory for RA in VSCode. My project uses lalrpop which puts generated files in this target directory. RA shows warnings in one of these autogenerated files (target-ra/debug/build/fml-738faf2a1534b33c/out/fml.rs). I think this is a bug because it doesn't show warnings if using the normal shared target directory and in general it makes no sense to show warns in files i can't do anything about.

It can be reproduced on this repo on the ra-bug branch. It contains a .vscode config that should contain everything needed - the warnings should be visible as soon as RA finishes analyzing the project:

Interestingly, there are other target-ra/debug/build/fml-*/out/fml.rs files but it only happens with this particular one.

Start by checking the .vscode configuration in the linked repository's ra-bug branch and reproducing the diagnostics in target-ra/debug/build/fml-738faf2a1534b33c/out/fml.rs. Then trace how rust-analyzer handles generated files under an alternative CARGO_TARGET_DIR. Done means warnings from autogenerated target files are suppressed without hiding relevant diagnostics from project source files.