Typing Rules Become Programs in Tree Calculus, All Theorems Mechanized in Rocq

teropa · x · 2026-11-05

Barry Jay released a new paper showing that in tree calculus, typing rules become programs: type inference is just evaluation (infer @ t ⟹ Sm T), and type application replaces function types, type variables, and quantifiers—no stratified type hierarchy needed. The system supports general recursion, polymorphic lists, type-directed conditionals, length-indexed arrays, queries and updates, with a type-inference program that types itself. All theorems are mechanized in Rocq, with proofs open-sourced on GitHub under MIT license.

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