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| author |  Gaëtan Gilbert <gaetan.gilbert@skyskimmer.net> | 2018-02-16 15:44:44 +0100 |
|---|---|---|
| committer | Gaëtan Gilbert <gaetan.gilbert@skyskimmer.net> | 2018-03-09 16:29:06 +0100 |
| commit | 17a0dccfe91d6f837ce285e62b8d843720f8c1a1 (patch) | |
| tree | 605a2dae6692cec6503ab5fcdce7c90421db26f0 /vernac | |
| parent | 3d86afb36517c9ba4200289e169239f7fa54fca1 (diff) | |
Allow using cumulativity without forcing strict constraints.
Previously [fun x : Ind@{i} => x : Ind@{j}] with Ind some cumulative
inductive would try to generate a constraint [i = j] and use
cumulativity only if this resulted in an inconsistency. This is
confusingly different from the behaviour with [Type] and means
cumulativity can only be used to lift between universes related by
strict inequalities. (This isn't a kernel restriction so there might
be some workaround to send the kernel the right constraints, but
not in a nice way.)
See modified test for more details of what is now possible.
Technical notes:
When universe constraints were inferred by comparing the shape of
terms without reduction, cumulativity was not used and so too-strict
equality constraints were generated. Then in order to use cumulativity
we had to make this comparison fail to fall back to full conversion.
When unifiying 2 instances of a cumulative inductive type, if there
are any Irrelevant universes we try to unify them if they are
flexible.
Diffstat (limited to 'vernac')
| -rw-r--r-- | vernac/obligations.ml | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/vernac/obligations.ml b/vernac/obligations.ml index 4f16e1cf6..064e40b9b 100644 --- a/vernac/obligations.ml +++ b/vernac/obligations.ml @@ -1,5 +1,4 @@ open Printf -open Globnames open Libobject open Entries open Decl_kinds |