Clarify unused_doc_comments note on macro invocations

Author: dtolnay

src/librustc_lint/context.rs

@@ -566,7 +566,7 @@ pub trait LintContext: Sized {
                     stability::deprecation_suggestion(&mut db, suggestion, span)
                 }
                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
-                    db.span_label(span, "rustdoc does not generate documentation for macros");
+                    db.span_label(span, "rustdoc does not generate documentation for macro invocations");
                     db.help("to document an item produced by a macro, \
                                   the macro must produce the documentation as part of its expansion");
                 }

src/test/ui/useless-comment.stderr

@@ -2,7 +2,7 @@ error: unused doc comment
   --> $DIR/useless-comment.rs:9:1
    |
 LL | /// foo
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ rustdoc does not generate documentation for macros
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ rustdoc does not generate documentation for macro invocations
    |
 note: the lint level is defined here
   --> $DIR/useless-comment.rs:3:9
@@ -15,7 +15,7 @@ error: unused doc comment
   --> $DIR/useless-comment.rs:32:5
    |
 LL |     /// bar
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ rustdoc does not generate documentation for macros
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ rustdoc does not generate documentation for macro invocations
    |
    = help: to document an item produced by a macro, the macro must produce the documentation as part of its expansion