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arXiv:1911.08174cs.LO

Failure of Normalization in Impredicative Type Theory with Proof-Irrelevant Propositional Equality

Andreas Abel, Thierry Coquand

Abstract

Normalization fails in type theory with an impredicative universe of propositions and a proof-irrelevant propositional equality. The counterexample to normalization is adapted from Girard's counterexample against normalization of System F equipped with a decider for type equality. It refutes Werner's normalization conjecture [LMCS 2008].

arXiv comments
Journal reference
Logical Methods in Computer Science, Volume 16, Issue 2 (June 30, 2020) lmcs:6068
DOI
doi:10.23638/LMCS-16(2:14)2020
Subjects
cs.LOLogic in Computer Science cs.PLProgramming Languages math.LOLogic

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Discussed in comments3 threads

    • A few notes, because this is obviously vibe coded, and does not work in many ways. 1. Yon's documentation mentions "Homotopy type theory:" > the runnable HoTT fragment is refl/pair/fst/snd These are basic features of martin-lof type theory, not homotopy type theory. The…

      omegafixedpointView on HNParent context

    • Some constructivists may also take offense with proof irrelevance (and the resulting loss of normalization [1] or its incompatibility with HoTT), which you can only really avoid by avoiding Prop. [1] https://arxiv.org/abs/1911.08174

      foooobarView on HNParent context

  1. Coq is a Lean Typechecker 1 comment
    • The normalization issue is not about quotients at all. It's https://arxiv.org/abs/1911.08174 "Failure of Normalization in Impredicative Type Theory with Proof-Irrelevant Propositional Equality"

      SkySkimmerView on HNParent context

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