add a required wrapper around plugin installers

While trying to expand the CoreMonad.reinitializeGlobals mechanism, I proposed an alternative that SPJ noted could be more generally useful.

The nub of the idea is to require plugins to apply a distinguished function to their installation function. Instead of defining the plugin as

module APlugin (plugin) where
import GhcPlugins

plugin :: Plugin
plugin = defaultPlugin {installCoreToDos = install}

install :: [CommandLineOption] -> [CoreToDo] -> CoreM [CoreToDo]
install = …

plugins would be defined as

module APlugin (plugin) where
import GhcPlugins

plugin :: Plugin
plugin = defaultPlugin {installCoreToDos = mkPluginInstaller install}

install :: [CommandLineOption] -> [CoreToDo] -> CoreM [CoreToDo]
install = install = …

The new function mkPluginInstaller provides a hook for GHC developers to process the plugin, hidden from the plugin author. For example, it could encapsulate the current reinitializeGlobals mechanism.

I'm not sure if using an abstract type to enforce that this function is called is necessary, but it's an option.

Trac metadata

Trac field	Value
Version	7.6.3
Type	Task
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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