Zulip Chat Archive
Stream: lean4
Topic: unfortunate error messages
Jason Gross (Mar 11 2021 at 20:39):
This is unfortunate:
instance OfNat_1 : OfNat Type 1 := { ofNat := Unit }
#check (1 : Type)
/-
2:9: failed to synthesize instance
OfNat Type 1
-/
Jason Gross (Mar 11 2021 at 20:39):
(I do see what's going on here, but it took me a couple minutes and set_option pp.all true
to puzzle it out)
Leonardo de Moura (Mar 11 2021 at 20:43):
We have some documentation here https://leanprover.github.io/lean4/doc/typeclass.html (Numerals section)
You are not the first person confused by this issue, we should probably just let people write these instances without the natLit!
.
Last updated: Dec 20 2023 at 11:08 UTC