sign() :: 1 | -1 seems to be an invalid typespec

[Mikhail Glushenkov]

If my reading of https://hexdocs.pm/elixir/1.12/typespecs.html#literals is correct, negative integer literals are not supported in typespecs.

Despite both the compiler and Dialyzer not complaining, this causes issues sometimes, for example here: pylon/spect#19

Suggestion: change the type of sign to sign() :: :positive | :negative or sign() :: integer()

[Wojtek Mach]

Elixir supports negative literals because Erlang does:

Erlang_Integer %% ..., -1, 0, 1, ... 42 ...

https://www.erlang.org/doc/reference_manual/typespec.html

a PR to Elixir typespecs page clarifying this would be appreciated.

if a negative integer literal was unsupported, Elixir compiler should fail to compile a module that uses it.

we cannot change to :positive | :negative as this would be a breaking change. integer() would be too broad.

i suspect the spec tool you are using isnt handling negative literals and that is the root cause.

im not on my computer so i cant do more tests but hope it is helpful anyway.

[Mikhail Glushenkov]

Thanks, this indeed turned out to be a problem with Spect!