Compatibility with GHC < 8.8

.hlint.yaml

@@ -96,6 +96,7 @@
   - default: false
   - {name: [-Wno-missing-signatures, -Wno-orphans, -Wno-overlapping-patterns, -Wno-incomplete-patterns, -Wno-missing-fields, -Wno-unused-matches]}
   - {name: [-Wno-dodgy-imports], within: Main}
+  - {name: [-Wno-dodgy-imports], within: Development.IDE.GHC.Compat}
 # - modules:
 #   - {name: [Data.Set, Data.HashSet], as: Set} # if you import Data.Set qualified, it must be as 'Set'
 #   - {name: Control.Arrow, within: []} # Certain modules are banned entirely

src/Development/IDE/GHC/Compat.hs

@@ -2,7 +2,10 @@
 -- SPDX-License-Identifier: Apache-2.0
 
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE PatternSynonyms #-}
+{-# OPTIONS -Wno-dodgy-imports #-}
 #include "ghc-api-version.h"
 
 -- | Attempt at hiding the GHC version differences we can.
@@ -43,6 +46,9 @@ module Development.IDE.GHC.Compat(
     pattern ModLocation,
     getConArgs,
 
+    HasSrcSpan,
+    getLoc,
+
     module GHC
     ) where
 
@@ -66,7 +72,9 @@ import GHC hiding (
       SigD,
       TypeSig,
       VarPat,
-      ModLocation
+      ModLocation,
+      HasSrcSpan,
+      getLoc
 #if MIN_GHC_API_VERSION(8,6,0)
     , getConArgs
 #endif
@@ -104,7 +112,7 @@ import System.IO.Error
 import Binary
 import Control.Exception (catch)
 import Data.ByteString (ByteString)
-import GhcPlugins hiding (ModLocation)
+import GhcPlugins (Hsc, srcErrorMessages)
 import NameCache
 import TcRnTypes
 import System.IO
@@ -325,7 +333,20 @@ getHeaderImports
        )
 #if MIN_GHC_API_VERSION(8,8,0)
 getHeaderImports = Hdr.getImports
+
+type HasSrcSpan = GHC.HasSrcSpan
+getLoc :: HasSrcSpan a => a -> SrcSpan
+getLoc = GHC.getLoc
+
 #else
+
+class HasSrcSpan a where
+    getLoc :: a -> SrcSpan
+instance HasSrcSpan Name where
+    getLoc = nameSrcSpan
+instance HasSrcSpan (GenLocated SrcSpan a) where
+    getLoc = GHC.getLoc
+
 getHeaderImports a b c d =
     catch (Right <$> Hdr.getImports a b c d)
           (return . Left . srcErrorMessages)

src/Development/IDE/Spans/Documentation.hs

@@ -18,7 +18,7 @@ import           Development.IDE.GHC.Compat
 import           Development.IDE.GHC.Error
 import           Development.IDE.Spans.Common
 import           FastString
-import SrcLoc
+import           SrcLoc (RealLocated)
 
 
 getDocumentationTryGhc