Function rustc_builtin_macros::source_util::resolve_path

fn resolve_path<'a>(
    cx: &mut ExtCtxt<'a>, 
    path: impl Into<PathBuf>, 
    span: Span
) -> PResult<'a, PathBuf>

Resolves a path mentioned inside Rust code, returning an absolute path.

This unifies the logic used for resolving include_X!.