type-errors

Tools for writing better type errors

https://github.com/isovector/type-errors#readme

LTS Haskell 23.27:0.2.0.2@rev:1
Stackage Nightly 2025-07-12:0.2.0.2@rev:1
Latest on Hackage:0.2.0.2@rev:1

See all snapshots type-errors appears in

BSD-3-Clause licensed by Sandy Maguire
Maintained by [email protected]
This version can be pinned in stack with:type-errors-0.2.0.2@sha256:afd6b33bb582730a90ea58fd23d5b32a38b5b6c8b2f18e3250936bdc0487dfab,2513

Module documentation for 0.2.0.2

  • Type
    • Type.Errors
Used by 2 packages in nightly-2025-07-12(full list with versions):
clash-prelude, polysemy

type-errors

Build Status Hackage

Dedication

View the gradients of adversity as the colors that paint your story, and the power of experience as what makes you a great teacher, creator, philosopher, entrepreneur, artist, and human. Everything works out eventually.

Jennifer Sodini

Overview

type-errors is a collection of tools for writing better, more ergonomic, type errors. Some of the more interesting features are the ability to observe stuckedness and phantomness, as well as perform substitutions over types.

For more information, check out the haddock documentation.

Acknowledgments

This project wouldn’t be possible without the help of two amazing people:

  • kcsongor who came up with the original technology behind this library.
  • Lysxia for articulating the approach to making IfStuck work for things of all kinds, and for helping me with the substitution machinery.

Changes

Changelog for type-errors

0.2.0.2 (2023-04-08)

  • Bumped version bounds

0.2.0.1 (2022-11-24)

  • Bumped version bounds

0.2.0.0 (2019-07-03)

Breaking Changes

  • The UnlessPhantom and various Subst type families were broken in the presence of stuckness. This rendered them almost entirely unusable — so they now have a new implementation in terms of te.
  • Added te, a TemplateHaskell splice, which will perform symbolic substitutions over types. See haddock for the migration details.

Unreleased changes