Enable compatibility with the next version of HLint (#434)

* Use Just True == in preference to fromMaybe True or similar

* Use trimStart instead of dropWhile isSpace

* Whitespace only

* Remove a redundant import

* Enable HLint hints suggesting the extra library

fmt.sh

@@ -1,3 +1,3 @@
 #!/usr/bin/env bash
 set -eou pipefail
-curl -sSL https://raw.github.com/ndmitchell/hlint/master/misc/run.sh | sh -s .
+curl -sSL https://raw.github.com/ndmitchell/hlint/master/misc/run.sh | sh -s . --with-group=extra

src/Development/IDE/Plugin/CodeAction.hs

@@ -343,7 +343,7 @@ topOfHoleFitsMarker =
 
 mkRenameEdit :: Maybe T.Text -> Range -> T.Text -> TextEdit
 mkRenameEdit contents range name =
-    if fromMaybe False maybeIsInfixFunction
+    if maybeIsInfixFunction == Just True
       then TextEdit range ("`" <> name <> "`")
       else TextEdit range name
   where

src/Development/IDE/Plugin/Completions/Logic.hs

@@ -195,7 +195,7 @@ mkImportCompl enteredQual label =
   CompletionItem m (Just CiModule) (Just label)
     Nothing Nothing Nothing Nothing Nothing Nothing Nothing
     Nothing Nothing Nothing Nothing Nothing
-  where 
+  where
     m = fromMaybe "" (T.stripPrefix enteredQual label)
 
 mkExtCompl :: T.Text -> CompletionItem
@@ -303,7 +303,7 @@ toggleSnippets ClientCapabilities { _textDocument } (WithSnippets with) x
   | otherwise = x { _insertTextFormat = Just PlainText
                   , _insertText       = Nothing
                   }
-  where supported = fromMaybe False (_textDocument >>= _completion >>= _completionItem >>= _snippetSupport)
+  where supported = Just True == (_textDocument >>= _completion >>= _completionItem >>= _snippetSupport)
 
 -- | Returns the cached completions for the given module and position.
 getCompletions :: IdeOptions -> CachedCompletions -> TypecheckedModule -> VFS.PosPrefixInfo -> ClientCapabilities -> WithSnippets -> IO [CompletionItem]
@@ -394,7 +394,7 @@ getCompletions ideOpts CC { allModNamesAsNS, unqualCompls, qualCompls, importabl
         = filtModNameCompls ++ map (toggleSnippets caps withSnippets
                                       . mkCompl ideOpts . stripAutoGenerated) filtCompls
                             ++ filtKeywordCompls
-  
+
   return result
 
 -- The supported languages and extensions
@@ -404,7 +404,7 @@ languagesAndExts = map T.pack $ DynFlags.supportedLanguagesAndExtensions ( Platf
 #else
 languagesAndExts = map T.pack DynFlags.supportedLanguagesAndExtensions
 #endif
-  
+
 -- ---------------------------------------------------------------------
 -- helper functions for pragmas
 -- ---------------------------------------------------------------------

src/Development/IDE/Spans/Common.hs

@@ -18,6 +18,7 @@ module Development.IDE.Spans.Common (
 import Data.Data
 import qualified Data.Generics
 import qualified Data.Text as T
+import Data.List.Extra
 
 import GHC
 import Outputable
@@ -28,7 +29,6 @@ import DataCon
 import Var
 #endif
 
-import           Data.Char (isSpace)
 import qualified Documentation.Haddock.Parser as H
 import qualified Documentation.Haddock.Types as H
 
@@ -135,9 +135,9 @@ haddockToMarkdown (H.DocHeader (H.Header level title))
   = replicate level '#' ++ " " ++ haddockToMarkdown title
 
 haddockToMarkdown (H.DocUnorderedList things)
-  = '\n' : (unlines $ map (("+ " ++) . dropWhile isSpace . splitForList . haddockToMarkdown) things)
+  = '\n' : (unlines $ map (("+ " ++) . trimStart . splitForList . haddockToMarkdown) things)
 haddockToMarkdown (H.DocOrderedList things)
-  = '\n' : (unlines $ map (("1. " ++) . dropWhile isSpace . splitForList . haddockToMarkdown) things)
+  = '\n' : (unlines $ map (("1. " ++) . trimStart . splitForList . haddockToMarkdown) things)
 haddockToMarkdown (H.DocDefList things)
   = '\n' : (unlines $ map (\(term, defn) -> "+ **" ++ haddockToMarkdown term ++ "**: " ++ haddockToMarkdown defn) things)
 
@@ -159,4 +159,4 @@ splitForList :: String -> String
 splitForList s
   = case lines s of
       [] -> ""
-      (first:rest) -> unlines $ first : map (("  " ++) . dropWhile isSpace) rest
+      (first:rest) -> unlines $ first : map (("  " ++) . trimStart) rest

src/Development/IDE/Types/Options.hs

@@ -14,7 +14,6 @@ module Development.IDE.Types.Options
   , defaultIdeOptions
   ) where
 
-import Data.Maybe
 import Development.Shake
 import Development.IDE.GHC.Util
 import           GHC hiding (parseModule, typecheckModule)
@@ -68,8 +67,8 @@ newtype IdeReportProgress = IdeReportProgress Bool
 newtype IdeDefer          = IdeDefer          Bool
 
 clientSupportsProgress :: LSP.ClientCapabilities -> IdeReportProgress
-clientSupportsProgress caps = IdeReportProgress $ fromMaybe False $
-    LSP._workDoneProgress =<< LSP._window (caps :: LSP.ClientCapabilities)
+clientSupportsProgress caps = IdeReportProgress $ Just True ==
+    (LSP._workDoneProgress =<< LSP._window (caps :: LSP.ClientCapabilities))
 
 defaultIdeOptions :: Action (FilePath -> Action HscEnvEq) -> IdeOptions
 defaultIdeOptions session = IdeOptions