Wingman: Ensure homomorphic destruct covers all constructors in the domain #1968
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pepeiborra
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Jun 23, 2021
jneira
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Jun 25, 2021
…omain (haskell#1968) * Ensure homomorphism covers the entire codomain * Add tests * Add the same logic to lambda case homomorphism Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
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This PR changes the behavior of the
homotactic, ensuring that it is total and well-typed to apply. Before, it would just automatically fill in the data constructors, regardless of whether they were the right type. The new logic is to check which data constructors are possible in the domain, and which in the codomain, and to subtract the latter from the former. If this set is non-empty, it means either the thing won't type check, or that due to some GADT equalities, it's impossible to map some constructors. Either way, the tactic should fail, and does now.Fixes #565