Plugins

Definitions for writing plugins for GHC. Plugins can hook into several areas of the compiler. See the Plugin type. These plugins include type-checker plugins, source plugins, and core-to-core plugins.

Plugins

data Plugin

Plugin is the compiler plugin data type. Try to avoid constructing one of these directly, and just modify some fields of defaultPlugin instead: this is to try and preserve source-code compatibility when we add fields to this.

Nonetheless, this API is preliminary and highly likely to change in the future.

Constructors

Plugin

Fields

• installCoreToDos :: CorePlugin

  Modify the Core pipeline that will be used for compilation. This is called as the Core pipeline is built for every module being compiled, and plugins get the opportunity to modify the pipeline in a nondeterministic order.

• tcPlugin :: TcPlugin

  An optional typechecker plugin, which may modify the behaviour of the constraint solver.

• holeFitPlugin :: HoleFitPlugin

  An optional plugin to handle hole fits, which may re-order or change the list of valid hole fits and refinement hole fits.

• dynflagsPlugin :: [CommandLineOption] -> DynFlags -> IO DynFlags

  An optional plugin to update DynFlags, right after plugin loading. This can be used to register hooks or tweak any field of DynFlags before doing actual work on a module.

  Since: 8.10.1

• pluginRecompile :: [CommandLineOption] -> IO PluginRecompile

  Specify how the plugin should affect recompilation.

• parsedResultAction :: [CommandLineOption] -> ModSummary -> HsParsedModule -> Hsc HsParsedModule

  Modify the module when it is parsed. This is called by HscMain when the parsing is successful.

• renamedResultAction :: [CommandLineOption] -> TcGblEnv -> HsGroup GhcRn -> TcM (TcGblEnv, HsGroup GhcRn)

  Modify each group after it is renamed. This is called after each HsGroup has been renamed.

• typeCheckResultAction :: [CommandLineOption] -> ModSummary -> TcGblEnv -> TcM TcGblEnv

  Modify the module when it is type checked. This is called at the very end of typechecking.

• spliceRunAction :: [CommandLineOption] -> LHsExpr GhcTc -> TcM (LHsExpr GhcTc)

  Modify the TH splice or quasiqoute before it is run.

• interfaceLoadAction :: forall lcl. [CommandLineOption] -> ModIface -> IfM lcl ModIface

  Modify an interface that have been loaded. This is called by LoadIface when an interface is successfully loaded. Not applied to the loading of the plugin interface. Tools that rely on information from modules other than the currently compiled one should implement this function.

defaultPlugin :: Plugin

Default plugin: does nothing at all, except for marking that safe inference has failed unless -fplugin-trustworthy is passed. For compatibility reaso you should base all your plugin definitions on this default value.

type CommandLineOption = String

Command line options gathered from the -PModule.Name:stuff syntax are given to you as this type

Recompilation checking

purePlugin :: [CommandLineOption] -> IO PluginRecompile

impurePlugin :: [CommandLineOption] -> IO PluginRecompile

flagRecompile :: [CommandLineOption] -> IO PluginRecompile

data PluginRecompile

Constructors

ForceRecompile

NoForceRecompile

MaybeRecompile Fingerprint

Instances

Semigroup PluginRecompile

Defined in Plugins

Methods

(<>) :: PluginRecompile -> PluginRecompile -> PluginRecompile

sconcat :: NonEmpty PluginRecompile -> PluginRecompile

stimes :: Integral b => b -> PluginRecompile -> PluginRecompile

Monoid PluginRecompile

Defined in Plugins

Methods

mempty :: PluginRecompile

mappend :: PluginRecompile -> PluginRecompile -> PluginRecompile

mconcat :: [PluginRecompile] -> PluginRecompile

Outputable PluginRecompile

Defined in Plugins

Methods

ppr :: PluginRecompile -> SDoc

pprPrec :: Rational -> PluginRecompile -> SDoc

Plugin types

Frontend plugins

data FrontendPlugin

Constructors

FrontendPlugin

Fields

• frontend :: FrontendPluginAction

defaultFrontendPlugin :: FrontendPlugin

type FrontendPluginAction = [String] -> [(String, Maybe Phase)] -> Ghc ()

Core plugins

Core plugins allow plugins to register as a Core-to-Core pass.

type CorePlugin = [CommandLineOption] -> [CoreToDo] -> CoreM [CoreToDo]

Typechecker plugins

Typechecker plugins allow plugins to provide evidence to the typechecker.

type TcPlugin = [CommandLineOption] -> Maybe TcPlugin

Source plugins

GHC offers a number of points where plugins can access and modify its front-end ("source") representation. These include:

• access to the parser result with parsedResultAction
• access to the renamed AST with renamedResultAction
• access to the typechecked AST with typeCheckResultAction
• access to the Template Haskell splices with spliceRunAction
• access to loaded interface files with interfaceLoadAction

keepRenamedSource :: [CommandLineOption] -> TcGblEnv -> HsGroup GhcRn -> TcM (TcGblEnv, HsGroup GhcRn)

A renamer plugin which mades the renamed source available in a typechecker plugin.

Hole fit plugins

hole fit plugins allow plugins to change the behavior of valid hole fit suggestions

data HoleFitPluginR

HoleFitPluginR adds a TcRef to hole fit plugins so that plugins can track internal state. Note the existential quantification, ensuring that the state cannot be modified from outside the plugin.

Internal

data PluginWithArgs

Constructors

PluginWithArgs

Fields

• paPlugin :: Plugin

  the actual callable plugin

• paArguments :: [CommandLineOption]

  command line arguments for the plugin

plugins :: DynFlags -> [PluginWithArgs]

pluginRecompile' :: PluginWithArgs -> IO PluginRecompile

data LoadedPlugin

A plugin with its arguments. The result of loading the plugin.

Constructors

LoadedPlugin

Fields

• lpPlugin :: PluginWithArgs

  the actual plugin together with its commandline arguments

• lpModule :: ModIface

  the module containing the plugin

lpModuleName :: LoadedPlugin -> ModuleName

data StaticPlugin

A static plugin with its arguments. For registering compiled-in plugins through the GHC API.

Constructors

StaticPlugin

Fields

• spPlugin :: PluginWithArgs

  the actual plugin together with its commandline arguments

mapPlugins :: DynFlags -> (Plugin -> [CommandLineOption] -> a) -> [a]

withPlugins :: Monad m => DynFlags -> PluginOperation m a -> a -> m a

Perform an operation by using all of the plugins in turn.

withPlugins_ :: Monad m => DynFlags -> ConstPluginOperation m a -> a -> m ()

Perform a constant operation by using all of the plugins in turn.