fix: warn on empty line outer AttrKind::DocComment

Author: jdswensen

clippy_lints/src/attrs.rs

@@ -622,7 +622,7 @@ impl EarlyLintPass for EarlyAttributes {
 fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
     let mut iter = item.attrs.iter().peekable();
     while let Some(attr) = iter.next() {
-        if matches!(attr.kind, AttrKind::Normal(..))
+        if (matches!(attr.kind, AttrKind::Normal(..)) || matches!(attr.kind, AttrKind::DocComment(..)))
             && attr.style == AttrStyle::Outer
             && is_present_in_source(cx, attr.span)
         {
@@ -639,13 +639,17 @@ fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::It
                 let lines = without_block_comments(lines);
 
                 if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
-                    span_lint(
-                        cx,
-                        EMPTY_LINE_AFTER_OUTER_ATTR,
-                        begin_of_attr_to_item,
-                        "found an empty line after an outer attribute. \
-                        Perhaps you forgot to add a `!` to make it an inner attribute?",
-                    );
+                    let lint_mst = match attr.kind {
+                        AttrKind::Normal(..) => {
+                            "found an empty line after an outer attribute. \
+                        Perhaps you forgot to add a `!` to make it an inner attribute?"
+                        },
+                        AttrKind::DocComment(..) => {
+                            "found an empty line after an outer doc comment. \
+                        Perhaps you need to use `//!` to make a comment on the module or remove the empty line?"
+                        },
+                    };
+                    span_lint(cx, EMPTY_LINE_AFTER_OUTER_ATTR, begin_of_attr_to_item, lint_mst);
                 }
             }
         }