Factor out runtime type validation
Factor out runtime type validation

Moves runtime type validation to its own function.
gabelevi/graphql-js,enaqx/graphql-js,tgriesser/graphql-js,gabelevi/graphql-js,baer/graphql-js,enaqx/graphql-js,tgriesser/graphql-js,enaqx/graphql-js,graphql/graphql-js,baer/graphql-js,jjergus/graphql-js,graphql/graphql-js,graphql/graphql-js,jjergus/graphql-js