Turn duplicated_attributes into a late lint

tests/ui/auxiliary/proc_macro_attr.rs

@@ -176,3 +176,17 @@ pub fn with_empty_docs(_attr: TokenStream, input: TokenStream) -> TokenStream {
     }
     .into()
 }
+
+#[proc_macro_attribute]
+pub fn duplicated_attr(_attr: TokenStream, input: TokenStream) -> TokenStream {
+    let item = parse_macro_input!(input as syn::Item);
+    let attrs: Vec<syn::Attribute> = vec![];
+    quote! {
+        #(#attrs)*
+        #[allow(unused)]
+        #[allow(unused)]
+        #[allow(unused)]
+        #item
+    }
+    .into()
+}

tests/ui/duplicated_attributes.rs

@@ -1,9 +1,14 @@
+//@aux-build:proc_macro_attr.rs
+
 #![warn(clippy::duplicated_attributes)]
 #![cfg(any(unix, windows))]
 #![allow(dead_code)]
 #![allow(dead_code)] //~ ERROR: duplicated attribute
 #![cfg(any(unix, windows))] // Should not warn!
 
+#[macro_use]
+extern crate proc_macro_attr;
+
 #[cfg(any(unix, windows, target_os = "linux"))]
 #[allow(dead_code)]
 #[allow(dead_code)] //~ ERROR: duplicated attribute
@@ -12,7 +17,10 @@ fn foo() {}
 
 #[cfg(unix)]
 #[cfg(windows)]
-#[cfg(unix)] //~ ERROR: duplicated attribute
+#[cfg(unix)] // cfgs are not handled
 fn bar() {}
 
+#[proc_macro_attr::duplicated_attr()] // Should not warn!
+fn babar() {}
+
 fn main() {}

tests/ui/duplicated_attributes.stderr

@@ -1,16 +1,16 @@
 error: duplicated attribute
-  --> tests/ui/duplicated_attributes.rs:4:10
+  --> tests/ui/duplicated_attributes.rs:6:10
    |
 LL | #![allow(dead_code)]
    |          ^^^^^^^^^
    |
 note: first defined here
-  --> tests/ui/duplicated_attributes.rs:3:10
+  --> tests/ui/duplicated_attributes.rs:5:10
    |
 LL | #![allow(dead_code)]
    |          ^^^^^^^^^
 help: remove this attribute
-  --> tests/ui/duplicated_attributes.rs:4:10
+  --> tests/ui/duplicated_attributes.rs:6:10
    |
 LL | #![allow(dead_code)]
    |          ^^^^^^^^^
@@ -18,38 +18,21 @@ LL | #![allow(dead_code)]
    = help: to override `-D warnings` add `#[allow(clippy::duplicated_attributes)]`
 
 error: duplicated attribute
-  --> tests/ui/duplicated_attributes.rs:9:9
+  --> tests/ui/duplicated_attributes.rs:14:9
    |
 LL | #[allow(dead_code)]
    |         ^^^^^^^^^
    |
 note: first defined here
-  --> tests/ui/duplicated_attributes.rs:8:9
+  --> tests/ui/duplicated_attributes.rs:13:9
    |
 LL | #[allow(dead_code)]
    |         ^^^^^^^^^
 help: remove this attribute
-  --> tests/ui/duplicated_attributes.rs:9:9
+  --> tests/ui/duplicated_attributes.rs:14:9
    |
 LL | #[allow(dead_code)]
    |         ^^^^^^^^^
 
-error: duplicated attribute
-  --> tests/ui/duplicated_attributes.rs:15:7
-   |
-LL | #[cfg(unix)]
-   |       ^^^^
-   |
-note: first defined here
-  --> tests/ui/duplicated_attributes.rs:13:7
-   |
-LL | #[cfg(unix)]
-   |       ^^^^
-help: remove this attribute
-  --> tests/ui/duplicated_attributes.rs:15:7
-   |
-LL | #[cfg(unix)]
-   |       ^^^^
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 

tests/ui/unnecessary_clippy_cfg.stderr

@@ -57,5 +57,41 @@ error: no need to put clippy lints behind a `clippy` cfg
 LL | #![cfg_attr(clippy, deny(clippy::non_minimal_cfg, clippy::maybe_misused_cfg))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `#![deny(clippy::non_minimal_cfg, clippy::maybe_misused_cfg)]`
 
-error: aborting due to 8 previous errors
+error: duplicated attribute
+  --> tests/ui/unnecessary_clippy_cfg.rs:8:26
+   |
+LL | #![cfg_attr(clippy, deny(dead_code, clippy::non_minimal_cfg, clippy::maybe_misused_cfg))]
+   |                          ^^^^^^^^^
+   |
+note: first defined here
+  --> tests/ui/unnecessary_clippy_cfg.rs:6:26
+   |
+LL | #![cfg_attr(clippy, deny(dead_code, clippy::non_minimal_cfg))]
+   |                          ^^^^^^^^^
+help: remove this attribute
+  --> tests/ui/unnecessary_clippy_cfg.rs:8:26
+   |
+LL | #![cfg_attr(clippy, deny(dead_code, clippy::non_minimal_cfg, clippy::maybe_misused_cfg))]
+   |                          ^^^^^^^^^
+   = note: `-D clippy::duplicated-attributes` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::duplicated_attributes)]`
+
+error: duplicated attribute
+  --> tests/ui/unnecessary_clippy_cfg.rs:17:25
+   |
+LL | #[cfg_attr(clippy, deny(dead_code, clippy::non_minimal_cfg, clippy::maybe_misused_cfg))]
+   |                         ^^^^^^^^^
+   |
+note: first defined here
+  --> tests/ui/unnecessary_clippy_cfg.rs:15:25
+   |
+LL | #[cfg_attr(clippy, deny(dead_code, clippy::non_minimal_cfg))]
+   |                         ^^^^^^^^^
+help: remove this attribute
+  --> tests/ui/unnecessary_clippy_cfg.rs:17:25
+   |
+LL | #[cfg_attr(clippy, deny(dead_code, clippy::non_minimal_cfg, clippy::maybe_misused_cfg))]
+   |                         ^^^^^^^^^
+
+error: aborting due to 10 previous errors
 

tests/ui/useless_attribute.fixed

@@ -1,6 +1,6 @@
 //@aux-build:proc_macro_derive.rs
 
-#![allow(unused)]
+#![allow(unused, clippy::duplicated_attributes)]
 #![warn(clippy::useless_attribute)]
 #![warn(unreachable_pub)]
 #![feature(rustc_private)]

tests/ui/useless_attribute.rs

@@ -1,6 +1,6 @@
 //@aux-build:proc_macro_derive.rs
 
-#![allow(unused)]
+#![allow(unused, clippy::duplicated_attributes)]
 #![warn(clippy::useless_attribute)]
 #![warn(unreachable_pub)]
 #![feature(rustc_private)]