Sound and complete bidirectional typechecking for higher-rank polymorphism with existentials and indexed types

@article{Dunfield2019SoundAC,
  title={Sound and complete bidirectional typechecking for higher-rank polymorphism with existentials and indexed types},
  author={Jana Dunfield and Neelakantan R. Krishnaswami},
  journal={Proceedings of the ACM on Programming Languages},
  year={2019},
  volume={3},
  pages={1 - 28}
}
Bidirectional typechecking, in which terms either synthesize a type or are checked against a known type, has become popular for its applicability to a variety of type systems, its error reporting, and its ease of implementation. [] Key Method This approach permits declarative rules for coverage of pattern matching, as well as support for first-class existential types using a focalized subtyping judgment.
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