Add a comment, connecting the seq to the test (#4367) that shows its usefulness

[ghc-hetmet.git] / compiler / basicTypes / SrcLoc.lhs

diff --git a/compiler/basicTypes/SrcLoc.lhs b/compiler/basicTypes/SrcLoc.lhs
index d3db866..d912beb 100644 (file)
--- a/compiler/basicTypes/SrcLoc.lhs
+++ b/compiler/basicTypes/SrcLoc.lhs
@@ -454,7 +454,7 @@ pprDefnLoc loc
 \begin{code}
 -- | We attach SrcSpans to lots of things, so let's have a datatype for it.
 data Located e = L SrcSpan e
-  deriving (Typeable, Data)
+  deriving (Eq, Ord, Typeable, Data)
 
 unLoc :: Located e -> e
 unLoc (L _ e) = e