Function check 

pub fn check(
    path_var: Option<&OsStr>,
    name: &str,
    ours: &Path,
    dispatcher: Option<&Path>,
) -> Shadowing

Compare what varve dispatches against what PATH would run.

dispatcher is varve’s OWN executable. This is not an optimisation — it is the whole correctness of the check. A varve shim is a symlink to the varve binary, not to the pinned tool: running rivet executes varve, which reads argv[0] and dispatches the pinned binary (the argv[0] mechanism that replaced the old shell scripts in v0.19.0). So a correctly installed shim canonicalises to varve, NOT to the tool, and a naive path comparison flags every properly configured machine as shadowed.

An earlier draft did exactly that, and its unit test passed because the test symlinked to the STORE — testing a mechanism varve does not use. The end-to-end run caught it.