effectful-plugin: A GHC plugin for improving disambiguation of effects.

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Instruct GHC to do a better job with disambiguation of effects.

See the README for more information.

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Change log CHANGELOG.md
Dependencies base (>=4.13 && <5), containers (>=0.5), effectful-core (>= && <, ghc (>=8.6 && <9.3), ghc-tcplugins-extra (>=0.3 && <0.5) [details]
License BSD-3-Clause
Author Andrzej Rybczak
Maintainer andrzej@rybczak.net
Revised Revision 3 made by arybczak at 2022-08-12T18:18:34Z
Category Control
Bug tracker https://github.com/haskell-effectful/effectful/issues
Source repo head: git clone https://github.com/haskell-effectful/effectful.git
Uploaded by arybczak at 2022-07-13T20:07:21Z
Distributions LTSHaskell:, NixOS:
Downloads 80 total (13 in the last 30 days)
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Status Docs available [build log]
Last success reported on 2022-07-13 [all 1 reports]

Readme for effectful-plugin-

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A GHC plugin for improving disambiguation of effects.


To enable the plugin, add the following GHC option to your project file:

ghc-options: -fplugin=Effectful.Plugin

What it does

The following code:

action :: [State Int, State String] :>> es => Eff es ()
action = do
  x <- get
  put (x + 1)

will not compile out of the box because GHC doesn't know that you meant to get an Int since the function + as well as the literal 1 are polymorphic. You have to write:

action :: [State Int, State String] :>> es => Eff es ()
action = do
  x <- get @Int
  put (x + 1)

Which is slightly annoying. This plugin tells GHC extra information so code like this can type-check without having to spell types to the compiler.


Thanks to Xy Ren for her work on cleff-plugin effectful-plugin is based on.