do not to_string, use display

Author: klensy

Diff for: src/librustdoc/html/format.rs

@@ -1296,7 +1296,7 @@ impl clean::Impl {
                         self.print_type(inner_type, f, use_absolute, cx)?;
                         write!(f, ">")?;
                     } else {
-                        write!(f, "{}<", anchor(ty.def_id(), last, cx).to_string())?;
+                        write!(f, "{}<", anchor(ty.def_id(), last, cx))?;
                         self.print_type(inner_type, f, use_absolute, cx)?;
                         write!(f, ">")?;
                     }