yants

This is a tiny type-checker for data in Nix, written in Nix.

Features

• Checking of primitive types (int, string etc.)
• Checking polymorphic types (option, list, either)
• Defining & checking struct/record types
• Defining & matching enum types
• Defining & matching sum types
• Defining function signatures (including curried functions)
• Types are composable! option string! list (either int (option float))!
• Type errors also compose!

Currently lacking:

• Any kind of inference
• Convenient syntax for attribute-set function signatures

Primitives & simple polymorphism

Structs

Nested structs!

Enums!

Functions!

Usage

1. Import into scope with with:

   {
     inputs.yants.url = "github:divnix/yants";
     outputs = inputs: {
       someType = with inputs.yants; # code using yants
     };
   }

2. Import into scope and add log context:

   {
     inputs.yants.url = "github:divnix/yants";
     outputs = inputs: let
       rootLogYants = inputs.yants "my-lib";
       leafLogYants = rootLogYants "leaf";
     in {
       someType = with leafLogYants; # code using yants
     };
   }

Please see my Nix one-pager for more generic information about the Nix language and what the above constructs mean.

Stability

The current API of Yants is not yet considered stable, but it works fine and should continue to do so even if used at an older version.

Yants' tests use Nix versions above 2.6 - compatibility with older versions is not guaranteed.