Add notion of ExeDependency for tool-depends and custom setup

Cabal/Cabal.cabal

@@ -210,6 +210,7 @@ library
     Distribution.Types.BuildType
     Distribution.Types.ComponentInclude
     Distribution.Types.Dependency
+    Distribution.Types.ExeDependency
     Distribution.Types.LegacyExeDependency
     Distribution.Types.PkgconfigDependency
     Distribution.Types.Executable

Cabal/Distribution/Parsec/Class.hs

@@ -42,6 +42,7 @@ import           Distribution.Types.BenchmarkType
                  (BenchmarkType (..))
 import           Distribution.Types.BuildType                 (BuildType (..))
 import           Distribution.Types.Dependency                (Dependency (..))
+import           Distribution.Types.ExeDependency             (ExeDependency (..))
 import           Distribution.Types.LegacyExeDependency       (LegacyExeDependency (..))
 import           Distribution.Types.PkgconfigDependency       (PkgconfigDependency (..))
 import           Distribution.Types.GenericPackageDescription (FlagName, mkFlagName)
@@ -136,6 +137,14 @@ instance Parsec Dependency where
         ver  <- parsec <|> pure anyVersion
         return (Dependency name ver)
 
+instance Parsec ExeDependency where
+    parsec = do
+        name <- lexemeParsec
+        _    <- P.char ':'
+        exe  <- lexemeParsec
+        ver  <- parsec <|> pure anyVersion
+        return (ExeDependency name exe ver)
+
 instance Parsec LegacyExeDependency where
     parsec = do
         name <- parsecMaybeQuoted nameP

Cabal/Distribution/Types/ExeDependency.hs

+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveGeneric #-}
+module Distribution.Types.ExeDependency
+  ( ExeDependency(..)
+  , qualifiedExeName
+  ) where
+
+import Prelude ()
+import Distribution.Compat.Prelude
+
+import Distribution.Package
+import Distribution.Types.ComponentName
+import Distribution.Types.UnqualComponentName
+import Distribution.Version ( VersionRange, anyVersion )
+
+import qualified Distribution.Compat.ReadP as Parse
+import Distribution.Compat.ReadP
+import Distribution.Text
+
+import Text.PrettyPrint ((<+>), text)
+
+-- | Describes a dependency on an executable from a package
+--
+data ExeDependency = ExeDependency
+                     PackageName
+                     UnqualComponentName -- name of executable component of package
+                     VersionRange
+                     deriving (Generic, Read, Show, Eq, Typeable, Data)
+
+instance Binary ExeDependency
+instance NFData ExeDependency where rnf = genericRnf
+
+instance Text ExeDependency where
+  disp (ExeDependency name exe ver) =
+    (disp name <<>> text ":" <<>> disp exe) <+> disp ver
+
+  parse = do name <- parse
+             _ <- Parse.char ':'
+             exe <- parse
+             Parse.skipSpaces
+             ver <- parse <++ return anyVersion
+             Parse.skipSpaces
+             return (ExeDependency name exe ver)
+
+qualifiedExeName :: ExeDependency -> ComponentName
+qualifiedExeName (ExeDependency _ ucn _) = CExeName ucn