Fl4m3Ph03n1x

Fl4m3Ph03n1x

Cannot understand warnings in Gradient

Background

I am now trying Gradual type checking, as a consequence I am giving a shot to Gradient. As I see it, this is an alternative to Dialyzer.

Problems

So, on my first ever code snippet, I started with a pure function:

defmodule TipCalculator do

  @spec getTipPercentage(List[String.t()]) :: non_neg_integer
  def getTipPercentage(names) do
    names_size = length(names)

    cond do
      names_size > 5 -> 20
      names_size > 0 -> 10
      true -> 0
    end
  end
end

From my point of view, my type checks are rather solid.
However, Gradient seems to have a different opinion:

===> Analyzing applications...
===> Compiling gradualizer
src/gradualizer.erl:45:2: Warning: opaque type top() is underspecified and therefore meaningless

src/typechecker.erl:3234:1: Warning: function type_check_cons_in/4 is unused
src/typechecker.erl:3247:1: Warning: function type_check_cons_union/4 is unused
src/typechecker.erl:4612:1: Warning: function verbose/3 is unused
src/typechecker.erl:4870:1: Warning: function gen_partition/3 is unused
src/typechecker.erl:4872:1: Warning: function paux/3 is unused

==> gradient
Compiling 14 files (.ex)
Generated gradient app
==> grokking_fp
Compiling 1 file (.ex)
warning: code block contains unused literal "\n" (remove the literal or assign it to _ to avoid warnings)
  lib/tip_calculator.ex: TipCalculator

Generated grokking_fp app
Typechecking files...
lib/tip_calculator.ex: Undefined remote type Access:get/2 on line 0

From what I can understand, this one piece of code (from a fresh project) has several issues:

  1. warning: code block contains unused literal “\n” (remove the literal or assign it to _ to avoid warnings)
  2. lib/tip_calculator.ex: Undefined remote type Access:get/2 on line 0

The fist one sounds like a warning credo (or a linter) would give me. So I am not really sure what do do with it. I am expecting a tool that does type checks only (maybe I am wrong?).

The second one, I have no idea.

Questions

What am I doing wrong?

Marked As Solved

Fl4m3Ph03n1x

Fl4m3Ph03n1x

Answer

I got confused a little bit, the correct typing was [String.t] and not List[String.t].

I will say however that:

lib/tip_calculator.ex: Undefined remote type Access:get/2 on line 0

Is not (to me) a very descriptive error message.
However, given the alternative (dialzyer) message is not much better:

lib/tip_calculator.ex:8:unknown_type
Unknown type: Access.get/2.

I will say however, the line number was an incredible help to find the issue.
With Gradient line 0 really threw me off.

Also Liked

OvermindDL1

OvermindDL1

The first thing about the warning looks like just a warning in the gradient’s source, not yours.

The second thing is because Access.get is how elixir desugars things like what looks like array accesses, so typing @spec getTipPercentage(List[String.t()]) :: non_neg_integer is actually typing @spec getTipPercentage(Access.get(List, String.t())) :: non_neg_integer, which doesn’t make much sense as a type. ^.^;

But yeah, that’s not an issue for erlang code, it’s just some of Elixir’s magic making the type error a bit weird.

Where Next?

Popular Backend topics Top

IhorYachmenov
Hello. I have an iOS app where needs a proxying website through private server(HTTP / HTTPS proxy), but its idea each time has some trou...
New
Kurisu
Hello and happy new year! I would like to buy a Ruby On Rails ebook for learning purpose. What would be the ROR equivalent of “Programm...
New
Ookma-Kyi
I am learning Elixir at the moment but am finding it difficult to learn. The issue is there aren’t any good tutorial sites out there when...
New
bsek43
Hello everyone, I’ve started learning Elixir and Phoenix few months ago and while I mostly grasped Elixir’s functional concepts and Phoe...
New
Fl4m3Ph03n1x
Background I am trying to get a Github Action working with Windows and Bakeware because I am trying to create a release using it. Howeve...
New
Fl4m3Ph03n1x
Background I am trying to find a cheap and easy way to create New Types in Elixir, and Records seem to be just what I would need. Probl...
New
MarkIden
Hi, Recommend pls your favorite learning resources in Go, with best books, podcasts etc.
/go
New
Fl4m3Ph03n1x
Background I am moving towards defined data structures in my application, and I find that TypedStruct is quite useful. Questions Howeve...
New
Fl4m3Ph03n1x
Background When trying to execute mix release on a Windows 11 machine for a Phoenix project I get the following error: * assembling mark...
New
Fl4m3Ph03n1x
Background I have a release file inside a tarball. However I want the final release to have some additional files and to move things aro...
New

Other popular topics Top

DevotionGeo
I know that these benchmarks might not be the exact picture of real-world scenario, but still I expect a Rust web framework performing a ...
New
Exadra37
I am thinking in building or buy a desktop computer for programing, both professionally and on my free time, and my choice of OS is Linux...
New
AstonJ
I have seen the keycaps I want - they are due for a group-buy this week but won’t be delivered until October next year!!! :rofl: The Ser...
New
Rainer
Not sure if following fits exactly this thread, or if we should have a hobby thread… For many years I’m designing and building model air...
New
Exadra37
I am asking for any distro that only has the bare-bones to be able to get a shell in the server and then just install the packages as we ...
New
Exadra37
Oh just spent so much time on this to discover now that RancherOS is in end of life but Rancher is refusing to mark the Github repo as su...
New
PragmaticBookshelf
“A Mystical Experience” Hero’s Journey with Paolo Perrotta @nusco Ever wonder how authoring books compares to writing articles?...
New
DevotionGeo
The V Programming Language Simple language for building maintainable programs V is already mentioned couple of times in the forum, but I...
New
First poster: bot
The overengineered Solution to my Pigeon Problem. TL;DR: I built a wifi-equipped water gun to shoot the pigeons on my balcony, controlle...
New
First poster: bot
zig/http.zig at 7cf2cbb33ef34c1d211135f56d30fe23b6cacd42 · ziglang/zig. General-purpose programming language and toolchain for maintaini...
New