tidy: Detect outdated workspaces in workspace list

src/tools/tidy/src/deps.rs

diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index 592ba9c..5dbb7a4 100644
--- a/src/tools/tidy/src/deps.rs
+++ b/src/tools/tidy/src/deps.rs
@@ -1,6 +1,7 @@
 //! Checks the licenses of third-party dependencies.
 
 use std::collections::{HashMap, HashSet};
+use std::fmt::{Display, Formatter};
 use std::fs::{File, read_dir};
 use std::io::Write;
 use std::path::Path;
@@ -14,6 +15,25 @@
 #[path = "../../../bootstrap/src/utils/proc_macro_deps.rs"]
 mod proc_macro_deps;
 
+#[derive(Clone, Copy)]
+struct ListLocation {
+    path: &'static str,
+    line: u32,
+}
+
+impl Display for ListLocation {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}:{}", self.path, self.line)
+    }
+}
+
+/// Creates a [`ListLocation`] for the current location (with an additional offset to the actual list start);
+macro_rules! location {
+    (+ $offset:literal) => {
+        ListLocation { path: file!(), line: line!() + $offset }
+    };
+}
+
 /// These are licenses that are allowed for all crates, including the runtime,
 /// rustc, tools, etc.
 #[rustfmt::skip]
@@ -87,6 +107,8 @@ pub(crate) struct WorkspaceInfo<'a> {
     pub(crate) submodules: &'a [&'a str],
 }
 
+const WORKSPACE_LOCATION: ListLocation = location!(+4);
+
 /// The workspaces to check for licensing and optionally permitted dependencies.
 // FIXME auto detect all cargo workspaces
 pub(crate) const WORKSPACES: &[WorkspaceInfo<'static>] = &[
@@ -242,19 +264,6 @@ pub(crate) struct WorkspaceInfo<'a> {
 
 const EXCEPTIONS_UEFI_QEMU_TEST: ExceptionList = &[];
 
-#[derive(Clone, Copy)]
-struct ListLocation {
-    path: &'static str,
-    line: u32,
-}
-
-/// Creates a [`ListLocation`] for the current location (with an additional offset to the actual list start);
-macro_rules! location {
-    (+ $offset:literal) => {
-        ListLocation { path: file!(), line: line!() + $offset }
-    };
-}
-
 const PERMITTED_RUSTC_DEPS_LOCATION: ListLocation = location!(+6);
 
 /// Crates rustc is allowed to depend on. Avoid adding to the list if possible.
@@ -641,6 +650,13 @@ pub fn check(root: &Path, cargo: &Path, tidy_ctx: TidyCtx) {
             .other_options(vec!["--locked".to_owned()]);
         let metadata = t!(cmd.exec());
 
+        // Check for packages which have been moved into a different workspace and not updated
+        let absolute_root =
+            if path == "." { root.to_path_buf() } else { t!(std::path::absolute(root.join(path))) };
+        let absolute_root_real = t!(std::path::absolute(&metadata.workspace_root));
+        if absolute_root_real != absolute_root {
+            check.error(format!("{path} is part of another workspace ({} != {}), remove from `WORKSPACES` ({WORKSPACE_LOCATION})", absolute_root.display(), absolute_root_real.display()));
+        }
         check_license_exceptions(&metadata, path, exceptions, &mut check);
         if let Some((crates, permitted_deps, location)) = crates_and_deps {
             let descr = crates.get(0).unwrap_or(&path);