Fix rustc running out of memory

Author: weiznich

juniper/src/validation/mod.rs

@@ -12,7 +12,7 @@ mod test_harness;
 
 pub use self::context::{RuleError, ValidatorContext};
 pub use self::input_value::validate_input_values;
-pub use self::multi_visitor::{MultiVisitor, MultiVisitorNil};
+pub use self::multi_visitor::MultiVisitorNil;
 pub(crate) use self::rules::visit_all_rules;
 pub use self::traits::Visitor;
 pub use self::visitor::visit;