1..2 in typespecs does not mean a range %Range{first: 1, last: 2}, rather
an integer from 1 to 2.On Tue, Apr 13, 2021 at 6:13 PM Felipe Stival <[email protected]> wrote: > Shouldn't we support custom step types (like we do for first and last) > like in this diff > <https://github.com/elixir-lang/elixir/compare/master...v0idpwn:patch-1>? > > Em terça-feira, 13 de abril de 2021 às 18:17:35 UTC+3, José Valim escreveu: > >> Given Dialyzer does not natively support stepped ranges, I don't think we >> should emulate them and have 1..10//1 and 1..10//2 to two very distinct >> things. :( >> >> On Tue, Apr 13, 2021 at 5:03 PM [email protected] <[email protected]> >> wrote: >> >>> While working with the v1.12.0 rc0 release, I wrote the following >>> typespec: >>> >>> @spec my_fun(1..10//2) :: boolean() >>> >>> which resulted in the following error: >>> >>> == Compilation error in file lib/foobar.ex == >>> ** (CompileError) lib/foobar.ex:6: type ..///3 undefined (no such type >>> in Foobar) >>> >>> My confusion stemmed from my belief that ranges in typespecs were >>> interpreted by Elixir and expanded at compile time (e.g. 1..10 to >>> 1|2|3|4|5|...) since the syntax (first..last) matches the Elixir range >>> syntax and Erlang has no native ranges. Of course, this was wrong because >>> while Erlang doesn't have ranges, *Dialyzer* does. >>> >>> While I can't think of the last time I wanted the contract of my >>> function to be "only accepts odd integers between 1 and 100", it also seems >>> like a curious omission. From the perspective of someone with good >>> knowledge of Elixir but limited knowledge of Erlang and Dialyzer, I had >>> originally believed that this was some kind of mistake or oversight. >>> >>> There also might be a use-case in providing additional information to >>> Dialyzer, such as: >>> @spec odd?(1..10//2) :: true >>> @spec odd?(2..10//2) :: false >>> >>> Would it be worth taking a type such as 1..10//2 and compiling it to >>> 1|3|5|7|9 for Dialyzer? >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "elixir-lang-core" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/elixir-lang-core/d9415490-4285-48fe-a863-4d778ccc962an%40googlegroups.com >>> <https://groups.google.com/d/msgid/elixir-lang-core/d9415490-4285-48fe-a863-4d778ccc962an%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- > You received this message because you are subscribed to the Google Groups > "elixir-lang-core" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/b164a0dc-572e-4ec6-b62b-7d2ddff33fa7n%40googlegroups.com > <https://groups.google.com/d/msgid/elixir-lang-core/b164a0dc-572e-4ec6-b62b-7d2ddff33fa7n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4LShG5tQZysaWzNU-kYYi5p4X0HA-gOtKYsfJHh07iGyQ%40mail.gmail.com.
