Reduce dependency requirements to what is in sid

dhall/dhall.cabal

@@ -402,7 +402,7 @@ Library
         filepath                    >= 1.4      && < 1.5 ,
         haskeline                   >= 0.7.2.1  && < 0.8 ,
         lens-family-core            >= 1.0.0    && < 1.3 ,
-        megaparsec                  >= 7.0.0    && < 7.1 ,
+        megaparsec                  >= 6.5.0    && < 7.1 ,
         memory                      >= 0.14     && < 0.15,
         mtl                         >= 2.2.1    && < 2.3 ,
         optparse-applicative        >= 0.14.0.0 && < 0.15,
@@ -415,7 +415,7 @@ Library
         template-haskell                           < 2.15,
         text                        >= 0.11.1.0 && < 1.3 ,
         transformers                >= 0.2.0.0  && < 0.6 ,
-        transformers-compat         >= 0.6.4    && < 0.7 ,
+        transformers-compat         >= 0.6.2    && < 0.7 ,
         unordered-containers        >= 0.1.3.0  && < 0.3 ,
         uri-encode                                 < 1.6 ,
         vector                      >= 0.11.0.0 && < 0.13

dhall/src/Dhall/Parser.hs

@@ -1,4 +1,5 @@
-{-# LANGUAGE RecordWildCards            #-}
+{-# LANGUAGE CPP             #-}
+{-# LANGUAGE RecordWildCards #-}
 
 -- | This module contains Dhall's parsing logic
 
@@ -42,13 +43,21 @@ exprA = completeExpression
 
 -- | A parsing error
 data ParseError = ParseError
+#if MIN_VERSION_megaparsec(7, 0, 0)
     { unwrap :: Text.Megaparsec.ParseErrorBundle Text Void
+#else
+    { unwrap :: Text.Megaparsec.ParseError Char Void
+#endif
     , input  :: Text
     }
 
 instance Show ParseError where
     show (ParseError {..}) =
+#if MIN_VERSION_megaparsec(7, 0, 0)
       "\n\ESC[1;31mError\ESC[0m: Invalid input\n\n" <> Text.Megaparsec.errorBundlePretty unwrap
+#else
+      "\n\ESC[1;31mError\ESC[0m: Invalid input\n\n" <> Text.Megaparsec.parseErrorPretty unwrap
+#endif
 
 instance Exception ParseError
 

dhall/src/Dhall/Parser/Combinators.hs

@@ -34,6 +34,9 @@ import qualified Dhall.Pretty
 import qualified Dhall.Util
 import qualified Dhall.Set
 import qualified Text.Megaparsec
+#if !MIN_VERSION_megaparsec(7, 0, 0)
+import qualified Text.Megaparsec.Char as Text.Megaparsec (satisfy)
+#endif
 import qualified Text.Megaparsec.Char
 import qualified Text.Parser.Char
 import qualified Text.Parser.Combinators
@@ -233,7 +236,11 @@ instance Text.Parser.Char.CharParsing Parser where
 
   notChar = Text.Megaparsec.Char.char
 
+#if MIN_VERSION_megaparsec(7, 0, 0)
   anyChar = Text.Megaparsec.anySingle
+#else
+  anyChar = Text.Megaparsec.Char.anyChar
+#endif
 
   string = fmap Data.Text.unpack . Text.Megaparsec.Char.string . fromString
 

dhall/src/Dhall/Parser/Expression.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                 #-}
 {-# LANGUAGE NamedFieldPuns      #-}
 {-# LANGUAGE RecordWildCards     #-}
 {-# LANGUAGE OverloadedLists     #-}
@@ -27,16 +28,47 @@ import qualified Data.Sequence
 import qualified Data.Text
 import qualified Data.Text.Encoding
 import qualified Text.Megaparsec
+#if !MIN_VERSION_megaparsec(7, 0, 0)
+import qualified Text.Megaparsec.Char as Text.Megaparsec
+#endif
 import qualified Text.Parser.Char
 
 import Dhall.Parser.Combinators
 import Dhall.Parser.Token
 
+getSourcePos :: Text.Megaparsec.MonadParsec e s m =>
+                m Text.Megaparsec.SourcePos
+getSourcePos =
+#if MIN_VERSION_megaparsec(7, 0, 0)
+    Text.Megaparsec.getSourcePos
+#else
+    Text.Megaparsec.getPosition
+#endif
+{-# INLINE getSourcePos #-}
+
+getOffset :: Text.Megaparsec.MonadParsec e s m => m Int
+#if MIN_VERSION_megaparsec(7, 0, 0)
+getOffset = Text.Megaparsec.stateOffset <$> Text.Megaparsec.getParserState
+#else
+getOffset = Text.Megaparsec.stateTokensProcessed <$> Text.Megaparsec.getParserState
+#endif
+{-# INLINE getOffset #-}
+
+setOffset :: Text.Megaparsec.MonadParsec e s m => Int -> m ()
+#if MIN_VERSION_megaparsec(7, 0, 0)
+setOffset o = Text.Megaparsec.updateParserState $ \(Text.Megaparsec.State s _ pst) ->
+  Text.Megaparsec.State s o pst
+#else
+setOffset o = Text.Megaparsec.updateParserState $ \(Text.Megaparsec.State s p _ stw) ->
+  Text.Megaparsec.State s p o stw
+#endif
+{-# INLINE setOffset #-}
+
 noted :: Parser (Expr Src a) -> Parser (Expr Src a)
 noted parser = do
-    before      <- Text.Megaparsec.getSourcePos
+    before      <- getSourcePos
     (tokens, e) <- Text.Megaparsec.match parser
-    after       <- Text.Megaparsec.getSourcePos
+    after       <- getSourcePos
     let src₀ = Src before after tokens
     case e of
         Note src₁ _ | laxSrcEq src₀ src₁ -> return e
@@ -240,10 +272,10 @@ completeExpression embedded = completeExpression_
             <|> alternative38
           where
             alternative00 = do
-                n <- Text.Megaparsec.getOffset
+                n <- getOffset
                 a <- try doubleLiteral
                 b <- if isInfinite a
-                       then Text.Megaparsec.setOffset n *> fail "double out of bounds"
+                       then setOffset n *> fail "double out of bounds"
                        else return a
                 return (DoubleLit b)
 
@@ -390,7 +422,7 @@ completeExpression embedded = completeExpression_
                     ) && c /= '$'
 
             unescapedCharacterSlow = do
-                _ <- Text.Megaparsec.single '$'
+                _ <- Text.Parser.Char.char '$'
                 return (Chunks [] "$")
 
             escapedCharacter = do