Add PathTemplate Parsec instance

Author: jgotoh

Cabal/src/Distribution/Simple/InstallDirs.hs

@@ -55,6 +55,7 @@ import Distribution.Compat.Prelude
 import Distribution.Compat.Environment (lookupEnv)
 import Distribution.Pretty
 import Distribution.Package
+import Distribution.Parsec
 import Distribution.System
 import Distribution.Compiler
 import Distribution.Simple.InstallDirs.Internal
@@ -462,6 +463,12 @@ instance Read PathTemplate where
                   | (path, s')     <- readsPrec p s
                   , (template, "") <- reads path ]
 
+instance Parsec PathTemplate where
+  parsec = parsecPathTemplate
+
+parsecPathTemplate :: CabalParsing m => m PathTemplate
+parsecPathTemplate = parsecFilePath >>= return . toPathTemplate
+
 -- ---------------------------------------------------------------------------
 -- Internal utilities