useless_attribute: Add unreachable_pub to whitelists

Author: taiki-e

clippy_lints/src/attrs.rs

@@ -50,9 +50,9 @@ declare_clippy_lint! {
     /// **What it does:** Checks for `extern crate` and `use` items annotated with
     /// lint attributes.
     ///
-    /// This lint whitelists `#[allow(unused_imports)]` and `#[allow(deprecated)]` on
-    /// `use` items and `#[allow(unused_imports)]` on `extern crate` items with a
-    /// `#[macro_use]` attribute.
+    /// This lint whitelists `#[allow(unused_imports)]`, `#[allow(deprecated)]` and
+    /// `#[allow(unreachable_pub)]` on `use` items and `#[allow(unused_imports)]` on
+    /// `extern crate` items with a `#[macro_use]` attribute.
     ///
     /// **Why is this bad?** Lint attributes have no effect on crate imports. Most
     /// likely a `!` was forgotten.
@@ -240,13 +240,14 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Attributes {
                         if let Some(ident) = attr.ident() {
                             match &*ident.as_str() {
                                 "allow" | "warn" | "deny" | "forbid" => {
-                                    // whitelist `unused_imports` and `deprecated` for `use` items
+                                    // whitelist `unused_imports`, `deprecated` and `unreachable_pub` for `use` items
                                     // and `unused_imports` for `extern crate` items with `macro_use`
                                     for lint in lint_list {
                                         match item.node {
                                             ItemKind::Use(..) => {
                                                 if is_word(lint, *sym::unused_imports)
                                                     || is_word(lint, *sym::deprecated)
+                                                    || is_word(lint, *sym::unreachable_pub)
                                                 {
                                                     return;
                                                 }

clippy_lints/src/utils/sym.rs

@@ -363,6 +363,7 @@ symbols_simple! {
     uninit,
     uninitialized,
     unreachable,
+    unreachable_pub,
     unused_extern_crates,
     unused_imports,
     unwrap,

tests/ui/useless_attribute.rs

@@ -1,6 +1,7 @@
 // aux-build:proc_macro_derive.rs
 
 #![warn(clippy::useless_attribute)]
+#![warn(unreachable_pub)]
 
 #[allow(dead_code)]
 #[cfg_attr(feature = "cargo-clippy", allow(dead_code))]
@@ -32,4 +33,16 @@ pub use foo::Bar;
 #[derive(DeriveSomething)]
 struct Baz;
 
+// don't lint on unreachable_pub for `use` items
+mod a {
+    mod b {
+        #[allow(dead_code)]
+        #[allow(unreachable_pub)]
+        pub struct C {}
+    }
+
+    #[allow(unreachable_pub)]
+    pub use b::C;
+}
+
 fn main() {}