add limitation

Author: lmeller-git

clippy_lints/src/disallowed_modules.rs

@@ -20,7 +20,8 @@ declare_clippy_lint! {
     ///
     /// ### Why is this bad?
     /// Some modules are undesirable in certain contexts.
-    ///
+    /// ### Known limitations
+    /// Items that are not defined in the banned module and not imported via the banned module are not flagged.
     /// ### Example:
     /// An example clippy.toml configuration:
     /// ```toml
@@ -132,12 +133,11 @@ pub fn def_kind_predicate(def_kind: DefKind) -> bool {
 impl<'tcx> LateLintPass<'tcx> for DisallowedModules {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx rustc_hir::Item<'tcx>) {
         match item.kind {
-            ItemKind::Use(path, UseKind::Single(_) | UseKind::Glob) => {
+            ItemKind::Use(path, UseKind::Single(_) | UseKind::Glob)
                 if self.check_path_segments(cx, path.segments.iter(), path.span).is_some()
-                    && let Some(res) = path.res.type_ns
-                {
-                    self.check_res_emit(cx, &res, path.span);
-                }
+                    && let Some(res) = path.res.type_ns =>
+            {
+                self.check_res_emit(cx, &res, path.span);
             },
             ItemKind::Impl(impl_trait)
                 if let Some(trait_ref) = impl_trait.of_trait

tests/ui-toml/disallowed_modules/disallowed_modules.rs

@@ -27,15 +27,15 @@ use syn::token::Token;
 
 mod inner {
     // allow import via this module
-    pub mod sync {
-        #![allow(clippy::disallowed_modules)]
-        pub use std::sync::*;
-    }
+    #![allow(clippy::disallowed_modules)]
+    pub use std::sync::{Mutex, Weak};
 }
 
-// Does not get flagged because DefID parent is alloc::sync, not std::sync, and path is inner::Weak,
-// not std::sync::Weak.
-use inner::sync::Weak;
+// Weak does not get flagged because it is defined in alloc::sync, which is not banned, not
+// std::sync and its path is inner::Weak, which is also not banned, not std::sync::Weak.
+// Note that importing Mutex still fails, since it is defined in std::sync, which is banned.
+use inner::{Mutex as StdMutex, Weak as InnerWeak};
+//~^ disallowed_modules
 
 type DisallowedAlias = std::collections::BTreeMap<u32, u32>;
 //~^ disallowed_modules

tests/ui-toml/disallowed_modules/disallowed_modules.stderr

@@ -69,6 +69,12 @@ error: use of a disallowed module `syn::token`
 LL | use syn::token::Token;
    |     ^^^^^^^^^^^^^^^^^
 
+error: use of a disallowed module `std::sync`
+  --> tests/ui-toml/disallowed_modules/disallowed_modules.rs:37:13
+   |
+LL | use inner::{Mutex as StdMutex, Weak as InnerWeak};
+   |             ^^^^^
+
 error: use of a disallowed module `std::collections`
   --> tests/ui-toml/disallowed_modules/disallowed_modules.rs:40:24
    |
@@ -315,5 +321,5 @@ LL |         && let Some(std::net::Shutdown::Both) = None
    |
    = note: no net allowed
 
-error: aborting due to 50 previous errors
+error: aborting due to 51 previous errors