Verified type checkers
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Certification of a Type Inference Tool for ML: Damas–Milner within Coq by Catherine Dubois and Valérie Ménissier-Morain
Formalization of a Polymorphic Subtyping Algorithm by Jinxu Zhao, Bruno C. d. S. Oliveira, and Tom Schrijvers
type-inference formalization in Coq, based on A Rewriting Semantics for Type Inference