New function: 'relaxUpperBound :: VersionRange -> VersionRange'.

Cabal/Distribution/Version.hs

@@ -68,6 +68,9 @@ module Distribution.Version (
   foldVersionRange,
   foldVersionRange',
 
+  -- ** Modification
+  relaxUpperBound,
+
   -- * Version intervals view
   asVersionIntervals,
   VersionInterval,
@@ -237,6 +240,18 @@ betweenVersionsInclusive v1 v2 =
 {-# DEPRECATED betweenVersionsInclusive
     "In practice this is not very useful because we normally use inclusive lower bounds and exclusive upper bounds" #-}
 
+-- | Given a version range, remove the highest upper bound. Example: @(>= 1 && <
+-- 3) || (>= 4 && < 5)@ is converted to @(>= 1 && < 3) || (>= 4)@.
+relaxUpperBound :: VersionRange -> VersionRange
+relaxUpperBound = fromVersionIntervals . relaxLastInterval . toVersionIntervals
+  where
+    relaxLastInterval (VersionIntervals intervals) =
+      VersionIntervals (relaxLastInterval' intervals)
+
+    relaxLastInterval' []      = []
+    relaxLastInterval' [(l,_)] = [(l, NoUpperBound)]
+    relaxLastInterval' (i:is)  = i : relaxLastInterval' is
+
 -- | Fold over the basic syntactic structure of a 'VersionRange'.
 --
 -- This provides a syntacic view of the expression defining the version range.