Plugins: Add documentation and missing exports

Summary:
Previously the TcPlugin and CorePlugin type synonyms were not exporting,
resulting in much confusion.

Reviewers: mpickering

Reviewed By: mpickering

Subscribers: rwbarton, carter

Differential Revision: https://phabricator.haskell.org/D5237

2 files changed, 33 insertions, 5 deletions

diff --git a/compiler/main/Plugins.hs b/compiler/main/Plugins.hs
index 01a9841119..430b0790f9 100644
--- a/compiler/main/Plugins.hs
+++ b/compiler/main/Plugins.hs
@@ -1,11 +1,39 @@
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE CPP #-}
 module Plugins (
-      FrontendPlugin(..), defaultFrontendPlugin, FrontendPluginAction
-    , Plugin(..), CommandLineOption, LoadedPlugin(..), lpModuleName
-    , defaultPlugin, keepRenamedSource, withPlugins, withPlugins_
-    , PluginRecompile(..)
+      -- * Plugins
+      Plugin(..)
+    , defaultPlugin
+    , CommandLineOption
+      -- ** Recompilation checking
     , purePlugin, impurePlugin, flagRecompile
+    , PluginRecompile(..)
+
+      -- * Plugin types
+      -- ** Frontend plugins
+    , FrontendPlugin(..), defaultFrontendPlugin, FrontendPluginAction
+      -- ** Core plugins
+      -- | Core plugins allow plugins to register as a Core-to-Core pass.
+    , CorePlugin
+      -- ** Typechecker plugins
+      -- | Typechecker plugins allow plugins to provide evidence to the
+      -- typechecker.
+    , 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
+
+      -- * Internal
+    , LoadedPlugin(..), lpModuleName
+    , withPlugins, withPlugins_
     ) where
 
 import GhcPrelude
diff --git a/compiler/typecheck/TcRnDriver.hs b/compiler/typecheck/TcRnDriver.hs
index 1c04327bae..a0a837e886 100644
--- a/compiler/typecheck/TcRnDriver.hs
+++ b/compiler/typecheck/TcRnDriver.hs
@@ -2821,7 +2821,7 @@ withTcPlugins hsc_env m =
     do s <- runTcPluginM start ev_binds_var
        return (solve s, stop s)
 
-getTcPlugins :: DynFlags -> [TcPlugin]
+getTcPlugins :: DynFlags -> [TcRnMonad.TcPlugin]
 getTcPlugins dflags = catMaybes $ map get_plugin (plugins dflags)
   where get_plugin p = tcPlugin (lpPlugin p) (lpArguments p)