The goal of this project is to make prototypical implementation of a plugin for the Glasgow Haskell Compiler (GHC), such that the GHC can be used to compile strict Standard ML-style programs.
This plugin only works with GHC 9.2 and cannot be used with other versions.
The plugin can be activated within a module by adding both
{-# OPTIONS_GHC -fplugin Plugin.SMLPlugin #-} to the top of the file.
This brings a few basic functions, data types and type classes into scope, as well as some side-effect operations.
To evaluate an ML-Style computation, the user can import the computation in an ordinary Haskell module and use a function from Plugin.SMLPlugin.Encapsulation to execute it.
A sandbox project with examples is available to play around with in sandbox/. It can be loaded by executing stack repl sandbox from the root of the repository.
- Adding instances of derivable type classes to primitive types is not possible
- Most Language extensions are unsupported and will crash at compilation or run-time, but some of the extensions might work.
- Sharing in let-expressions does not work in some edge-cases
- Using
:rin GHCi only works on the second try - Type errors sometimes mention the effectful versions of type constructors
- HIE and HaskellLanguageServer do not work
Stack outputs some decoding failures while compiling the project. This can be ignored safely.Fixed with stack version 2.3.3
In order see, when my plugin generates invalid code, use the GHC option -dcore-lint. This type checks the generated core-code and emits an error message when something went wrong. I am very interested in finding those issues.
This option can also be turned on via {-# OPTIONS_GHC -dcore-lint #-}