Mechanizing Synthetic Tait Computability in Istari

Fuente: arXiv
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Autores principales: Li, Runming, Yao, Yue, Harper, Robert
Formato: Preprint
Publicado: 2025
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author Li, Runming
Yao, Yue
Harper, Robert
author_facet Li, Runming
Yao, Yue
Harper, Robert
contents Categorical gluing is a powerful technique for proving meta-theorems of type theories such as canonicity and normalization. Synthetic Tait Computability (STC) provides an abstract treatment of the complex gluing models by internalizing the gluing category into a modal dependent type theory with a phase distinction. This work presents a mechanization of STC in the Istari proof assistant. Istari is a Martin-Löf-style extensional type theory with equality reflection, which avoids much of the explicit transport reasoning typically found in intensional proof assistants. This work develops a reusable library for synthetic phase distinction, including modalities, extension types, and strict glue types, and applies it to two case studies: (1) a canonicity model for dependent type theory with dependent products and booleans with large elimination, and (2) a Kripke canonicity model for the cost-aware logical framework. Our results demonstrate that the core STC constructions can be formalized essentially verbatim in Istari, preserving the elegance of the on-paper arguments while ensuring machine-checked correctness.
format Preprint
id arxiv_https___arxiv_org_abs_2509_11418
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Mechanizing Synthetic Tait Computability in Istari
Li, Runming
Yao, Yue
Harper, Robert
Programming Languages
Categorical gluing is a powerful technique for proving meta-theorems of type theories such as canonicity and normalization. Synthetic Tait Computability (STC) provides an abstract treatment of the complex gluing models by internalizing the gluing category into a modal dependent type theory with a phase distinction. This work presents a mechanization of STC in the Istari proof assistant. Istari is a Martin-Löf-style extensional type theory with equality reflection, which avoids much of the explicit transport reasoning typically found in intensional proof assistants. This work develops a reusable library for synthetic phase distinction, including modalities, extension types, and strict glue types, and applies it to two case studies: (1) a canonicity model for dependent type theory with dependent products and booleans with large elimination, and (2) a Kripke canonicity model for the cost-aware logical framework. Our results demonstrate that the core STC constructions can be formalized essentially verbatim in Istari, preserving the elegance of the on-paper arguments while ensuring machine-checked correctness.
title Mechanizing Synthetic Tait Computability in Istari
topic Programming Languages
url https://arxiv.org/abs/2509.11418