Remove hidden code lines in Clippy's lint list

clippy_lints/src/utils/internal_lints/metadata_collector.rs

@@ -512,12 +512,21 @@ fn extract_attr_docs(cx: &LateContext<'_>, item: &Item<'_>) -> Option<String> {
     let mut lines = attrs.iter().filter_map(ast::Attribute::doc_str);
     let mut docs = String::from(&*lines.next()?.as_str());
     let mut in_code_block = false;
+    let mut is_code_block_rust = false;
     for line in lines {
-        docs.push('\n');
         let line = line.as_str();
         let line = &*line;
+
+        // Rustdoc hides code lines starting with `# ` and this removes them from Clippy's lint list :)
+        if is_code_block_rust && line.trim_start().starts_with("# ") {
+            continue;
+        }
+
+        // The line should be represented in the lint list, even if it's just an empty line
+        docs.push('\n');
         if let Some(info) = line.trim_start().strip_prefix("```") {
             in_code_block = !in_code_block;
+            is_code_block_rust = false;
             if in_code_block {
                 let lang = info
                     .trim()
@@ -528,6 +537,8 @@ fn extract_attr_docs(cx: &LateContext<'_>, item: &Item<'_>) -> Option<String> {
                     .unwrap_or("rust");
                 docs.push_str("```");
                 docs.push_str(lang);
+
+                is_code_block_rust = lang == "rust";
                 continue;
             }
         }