add with_empty_docs attr macro & test cases for issue rust-lang#12377

Author: J-ZhengLi

tests/ui/auxiliary/proc_macro_attr.rs

@@ -163,3 +163,16 @@ pub fn rewrite_struct(_args: TokenStream, input: TokenStream) -> TokenStream {
 
     quote!(#item_struct).into()
 }
+
+#[proc_macro_attribute]
+pub fn with_empty_docs(_attr: TokenStream, input: TokenStream) -> TokenStream {
+    let item = parse_macro_input!(input as syn::Item);
+    let attrs: Vec<syn::Attribute> = vec![];
+    let doc_comment = "";
+    quote! {
+        #(#attrs)*
+        #[doc = #doc_comment]
+        #item
+    }
+    .into()
+}

tests/ui/empty_docs.rs

@@ -1,6 +1,9 @@
+//@aux-build:proc_macro_attr.rs
+
 #![allow(unused)]
 #![warn(clippy::empty_docs)]
 #![allow(clippy::mixed_attributes_style)]
+#![feature(extern_types)]
 
 mod outer {
     //!
@@ -67,3 +70,17 @@ mod outer {
         y: i32,
     }
 }
+
+mod issue_12377 {
+    use proc_macro_attr::with_empty_docs;
+
+    #[with_empty_docs]
+    extern "C" {
+        type Test;
+    }
+
+    #[with_empty_docs]
+    struct Foo {
+        a: u8,
+    }
+}

tests/ui/empty_docs.stderr

@@ -1,5 +1,5 @@
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:6:5
+  --> tests/ui/empty_docs.rs:9:5
    |
 LL |     //!
    |     ^^^
@@ -9,31 +9,31 @@ LL |     //!
    = help: to override `-D warnings` add `#[allow(clippy::empty_docs)]`
 
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:14:5
+  --> tests/ui/empty_docs.rs:17:5
    |
 LL |     ///
    |     ^^^
    |
    = help: consider removing or filling it
 
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:16:9
+  --> tests/ui/empty_docs.rs:19:9
    |
 LL |         ///
    |         ^^^
    |
    = help: consider removing or filling it
 
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:27:5
+  --> tests/ui/empty_docs.rs:30:5
    |
 LL |     #[doc = ""]
    |     ^^^^^^^^^^^
    |
    = help: consider removing or filling it
 
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:30:5
+  --> tests/ui/empty_docs.rs:33:5
    |
 LL | /     #[doc = ""]
 LL | |     #[doc = ""]
@@ -42,36 +42,54 @@ LL | |     #[doc = ""]
    = help: consider removing or filling it
 
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:37:5
+  --> tests/ui/empty_docs.rs:40:5
    |
 LL |     ///
    |     ^^^
    |
    = help: consider removing or filling it
 
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:50:13
+  --> tests/ui/empty_docs.rs:53:13
    |
 LL |             /*! */
    |             ^^^^^^
    |
    = help: consider removing or filling it
 
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:58:13
+  --> tests/ui/empty_docs.rs:61:13
    |
 LL |             ///
    |             ^^^
    |
    = help: consider removing or filling it
 
 error: empty doc comment
-  --> tests/ui/empty_docs.rs:66:9
+  --> tests/ui/empty_docs.rs:69:9
    |
 LL |         ///
    |         ^^^
    |
    = help: consider removing or filling it
 
-error: aborting due to 9 previous errors
+error: empty doc comment
+  --> tests/ui/empty_docs.rs:77:5
+   |
+LL |     #[with_empty_docs]
+   |     ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider removing or filling it
+   = note: this error originates in the attribute macro `with_empty_docs` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: empty doc comment
+  --> tests/ui/empty_docs.rs:82:5
+   |
+LL |     #[with_empty_docs]
+   |     ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider removing or filling it
+   = note: this error originates in the attribute macro `with_empty_docs` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 11 previous errors