diff options
Diffstat (limited to 'pretyping')
| -rw-r--r-- | pretyping/cases.ml | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/pretyping/cases.ml b/pretyping/cases.ml index d9a67d2b12..587fc32ecb 100644 --- a/pretyping/cases.ml +++ b/pretyping/cases.ml @@ -1914,9 +1914,24 @@ let build_inversion_problem ~program_mode loc env sigma tms t = it = None } } ] in (* [pb] is the auxiliary pattern-matching serving as skeleton for the return type of the original problem Xi *) - let s' = Retyping.get_sort_of !!env sigma t in - let sigma, s = Evd.new_sort_variable univ_flexible sigma in - let sigma = Evd.set_leq_sort !!env sigma s' s in + let s = Retyping.get_sort_of !!env sigma t in + let sigma, s = Sorts.(match s with + | SProp | Prop | Set -> + (* To anticipate a possible restriction on an elimination from + SProp, Prop or (impredicative) Set we preserve the sort of the + main branch, knowing that the default impossible case shall + always be coercible to one of those *) + sigma, s + | Type _ -> + (* If the sort has algebraic universes, we cannot use this sort a + type constraint for the impossible case; especially if the + default case is not the canonical one provided in Prop by Coq + but one given by the user, which may be in either sort (an + example is in Vector.caseS', even if this one can probably be + put in Prop too with some care) *) + let sigma, s' = Evd.new_sort_variable univ_flexible sigma in + let sigma = Evd.set_leq_sort !!env sigma s s' in + sigma, s') in let pb = { env = pb_env; pred = (*ty *) mkSort s; |