Dialyxir does not catch errors on returned annonimous functions

[Fl4m3Ph03n1x]

Environment

$ elixir -v
Erlang/OTP 24 [erts-12.2.1] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]
Elixir 1.13.2 (compiled with Erlang/OTP 24)

• Which version of Dialyxir are you using? (cat mix.lock | grep dialyxir):

  "dialyxir": {:hex, :dialyxir, "1.1.0", "c5aab0d6e71e5522e77beff7ba9e08f8e02bad90dfbeffae60eaf0cb47e29488", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "07ea8e49c45f15264ebe6d5b93799d4dd56a44036cf42d0ad9c960bc266c0b9a"},
  "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},

  Current behavior

Given the following code sample:

defmodule PracticingCurrying do

  @spec greater_than(integer()) :: (integer() -> String.t())
  def greater_than(min) do
    fn number -> number > min end
  end

end

Which clearly has a wrong typing, I get a success message:

$ mix dialyzer
Compiling 1 file (.ex)
Generated grokking_fp app
Finding suitable PLTs
Checking PLT...
[:compiler, :currying, :elixir, :gradient, :gradualizer, :kernel, :logger, :stdlib, :syntax_tools]
Looking up modules in dialyxir_erlang-24.2.1_elixir-1.13.2_deps-dev.plt
Finding applications for dialyxir_erlang-24.2.1_elixir-1.13.2_deps-dev.plt
Finding modules for dialyxir_erlang-24.2.1_elixir-1.13.2_deps-dev.plt
Checking 518 modules in dialyxir_erlang-24.2.1_elixir-1.13.2_deps-dev.plt
Adding 44 modules to dialyxir_erlang-24.2.1_elixir-1.13.2_deps-dev.plt
done in 0m24.18s
No :ignore_warnings opt specified in mix.exs and default does not exist.

Starting Dialyzer
[
  check_plt: false,
  init_plt: '/home/user/Workplace/fl4m3/grokking_fp/_build/dev/dialyxir_erlang-24.2.1_elixir-1.13.2_deps-dev.plt',
  files: ['/home/user/Workplace/fl4m3/grokking_fp/_build/dev/lib/grokking_fp/ebin/Elixir.ImmutableValues.beam',
   '/home/user/Workplace/fl4m3/grokking_fp/_build/dev/lib/grokking_fp/ebin/Elixir.PracticingCurrying.beam',
   '/home/user/Workplace/fl4m3/grokking_fp/_build/dev/lib/grokking_fp/ebin/Elixir.TipCalculator.beam'],
  warnings: [:unknown]
]
Total errors: 0, Skipped: 0, Unnecessary Skips: 0
done in 0m1.02s
done (passed successfully)

Expected behavior

I expected dialyzer to tell me the correct spec is @spec greater_than(integer()) :: (integer() -> bool()).

[jeremyjh]

This is out of scope for this project; this project is just a mix integration for the dialyzer included in OTP. I'd recommend asking about this on the Elixir forums.