apply some clippy suggestions

rustfmt-core/src/lists.rs

@@ -616,6 +616,7 @@ where
     }
 }
 
+#[cfg_attr(feature = "cargo-clippy", allow(too_many_arguments))]
 // Creates an iterator over a list's items with associated comments.
 pub fn itemize_list<'a, T, I, F1, F2, F3>(
     codemap: &'a CodeMap,

rustfmt-core/src/visitor.rs

@@ -200,7 +200,7 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
 
                 let snippet = self.snippet(mk_sp(
                     self.last_pos,
-                    attr_lo.unwrap_or(first_stmt.span.lo()),
+                    attr_lo.unwrap_or_else(|| first_stmt.span.lo()),
                 ));
                 let len = CommentCodeSlices::new(snippet)
                     .nth(0)
@@ -568,6 +568,7 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
         self.buffer.push_str(s);
     }
 
+    #[cfg_attr(feature = "cargo-clippy", allow(needless_pass_by_value))]
     fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
         if let Some(ref s) = rewrite {
             self.push_str(s);