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.

Popular Backend topics Top

New
Fl4m3Ph03n1x
Background I am trying out polymorphic typing with dialyzer. As an example I am using the famous Option type (aka, Maybe Monad) that is n...
New
MarkIden
Hi, Recommend pls your favorite learning resources in Go, with best books, podcasts etc.
/go
New
Fl4m3Ph03n1x
Background I have recently been delving into more functional code. My objective right now is to get something similar to the IO Monad (in...
New
Ora2pgnewbie
Wanted to check if there is a UI available to use Ora2pg tool.
New
Fl4m3Ph03n1x
Background I am moving towards defined data structures in my application, and I find that TypedStruct is quite useful. Questions Howeve...
New
harwind
I have a large SQL database with millions of records, and I’ve identified duplicate entries. What’s the most efficient way to find and re...
New
Fl4m3Ph03n1x
Background I have an umbrella project, where I run mix test from the root. In one of the apps, I am mocking the File module using the Mo...
New
ogoldberg
Any recommendations on good resources for learning Elixir, Phoenix, and Ash?
New
yamuna
Hi everyone, I’m trying to run deepseek-coder:6.7b-instruct-q4_K_M in Docker using Ollama to create an LLM that will be used by CrewAI a...
New

Other popular topics Top

AstonJ
What chair do you have while working… and why? Is there a ‘best’ type of chair or working position for developers?
New
PragmaticBookshelf
Rust is an exciting new programming language combining the power of C with memory safety, fearless concurrency, and productivity boosters...
New
AstonJ
Just done a fresh install of macOS Big Sur and on installing Erlang I am getting: asdf install erlang 23.1.2 Configure failed. checking ...
New
AstonJ
This looks like a stunning keycap set :orange_heart: A LEGENDARY KEYBOARD LIVES ON When you bought an Apple Macintosh computer in the e...
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
PragmaticBookshelf
Learn different ways of writing concurrent code in Elixir and increase your application's performance, without sacrificing scalability or...
New
Margaret
Hello everyone! This thread is to tell you about what authors from The Pragmatic Bookshelf are writing on Medium.
1139 25467 754
New
New
sir.laksmana_wenk
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc. However, I don’t...
New
AstonJ
If you’re getting errors like this: psql: error: connection to server on socket “/tmp/.s.PGSQL.5432” failed: No such file or directory ...
New