graphql-js

62a08fa9 - Replace all instances of `ObjMap<boolean>` with ES6 Set (#3688)

Replace all instances of `ObjMap<boolean>` with ES6 Set (#3688) Motivation: I was inspecting code for unrelated reason and just spotted this pattern. I think it worth to refactor it since it easier to understand intention looking on code that uses Set's has/add methods. Benchmark shows no measurable changes in CPU/memory usages.