Add 'imported-from' command.

Language/Haskell/GhcMod/Error.hs

@@ -80,7 +80,6 @@ gmeDoc e = case e of
                \ Try enabling them:" $$
               nest 4 (backticks $ text "cabal configure --enable-tests [--enable-benchmarks]")
 
-        backticks d = char '`' <> d <> char '`'
         ctxDoc = moduleDoc *** compsDoc
                  >>> first (<> colon) >>> uncurry (flip hang 4)
 
@@ -104,6 +103,27 @@ gmeDoc e = case e of
     GMETooManyCabalFiles cfs ->
         text $ "Multiple cabal files found. Possible cabal files: \""
                ++ intercalate "\", \"" cfs ++"\"."
+    GMEMissingHaddockInterface f ->
+        text ("Haddock interface file missing: " ++ f) $$
+        text "" $$
+        haddockSuggestion
+    GMENoVisibleExports moduleName package ->
+        text $ "Failed to find visible exports of \"" ++ moduleName ++ "\" in \"" ++ package ++ "\""
+
+  where
+
+    backticks d = char '`' <> d <> char '`'
+
+    haddockSuggestion =
+        text "- To generate Haddock docs for dependencies, try:" $$
+            nest 4 (backticks $ text "cabal install --enable-documentation --haddock-hyperlink-source --only-dependencies") $$
+        text "" $$
+        text "- or set" $$
+            nest 4 (backticks $ text "documentation: True") $$
+        text "in ~/.cabal/config" $$
+        text "" $$
+        text "- or with Stack:" $$
+            nest 4 (backticks $ text "stack haddock")
 
 ghcExceptionDoc :: GhcException -> Doc
 ghcExceptionDoc e@(CmdLineError _) =

Language/Haskell/GhcMod/Gap.hs

@@ -48,6 +48,10 @@ module Language.Haskell.GhcMod.Gap (
   , mkErrStyle'
   , everythingStagedWithContext
   , withCleanupSession
+  , ghcQualify
+  , ghcIdeclHiding
+  , ghc_sl_fs
+  , ghc_ms_textual_imps
   ) where
 
 import Control.Applicative hiding (empty)
@@ -118,6 +122,10 @@ import Control.DeepSeq (NFData(rnf))
 import Data.ByteString.Lazy.Internal (ByteString(..))
 #endif
 
+#if __GLASGOW_HASKELL__ >= 800
+import BasicTypes (sl_fs, StringLiteral)
+#endif
+
 import Bag
 import Lexer as L
 import Parser
@@ -687,3 +695,45 @@ withCleanupSession action = do
   df <- getSessionDynFlags
   GHC.defaultCleanupHandler df action
 #endif
+
+-- | Things for Language.Haskell.GhcMod.ImportedFrom
+
+#if __GLASGOW_HASKELL__ >= 710
+ghcQualify :: PrintUnqualified
+ghcQualify = reallyAlwaysQualify
+#else
+ghcQualify :: PrintUnqualified
+ghcQualify = alwaysQualify
+#endif
+
+#if __GLASGOW_HASKELL__ >= 710
+ghcIdeclHiding :: GHC.ImportDecl GHC.RdrName -> Maybe (Bool, SrcLoc.Located [GHC.LIE GHC.RdrName])
+ghcIdeclHiding = GHC.ideclHiding
+#else
+-- Here, we have
+--
+--     ideclHiding :: Maybe (Bool, [LIE name])
+--
+-- so we have to use noLoc to get a SrcLoc.Located type in the second part of the tuple.
+ghcIdeclHiding :: GHC.ImportDecl GHC.RdrName -> Maybe (Bool, SrcLoc.Located [GHC.LIE GHC.RdrName])
+ghcIdeclHiding x = case GHC.ideclHiding x of
+                    Just (b, lie)   -> Just (b, GHC.noLoc lie)
+                    Nothing         -> Nothing
+
+#endif
+
+#if __GLASGOW_HASKELL__ >= 800
+ghc_sl_fs :: StringLiteral -> FastString
+ghc_sl_fs = sl_fs
+#else
+ghc_sl_fs = id
+#endif
+
+
+ghc_ms_textual_imps :: GHC.ModSummary -> [Located (ImportDecl RdrName)]
+#if __GLASGOW_HASKELL__ >= 800
+-- What does GHC8 give in the first part of the tuple?
+ghc_ms_textual_imps ms = map (fmap simpleImportDecl . snd) (ms_textual_imps ms)
+#else
+ghc_ms_textual_imps = ms_textual_imps
+#endif