1 files changed, 46 insertions, 0 deletions
diff --git a/testsuite/tests/deriving/should_run/drvrun020.hs b/testsuite/tests/deriving/should_run/drvrun020.hs
new file mode 100644
index 0000000000..cf78a2a992
--- /dev/null
+++ b/testsuite/tests/deriving/should_run/drvrun020.hs
@@ -0,0 +1,46 @@
+-- A  nasty deriving test
+-- Note the "T2 T1 { f1=3 }" part!
+
+module Main where
+
+
+infix 4 :%%
+data T = Int :%% T
+ 	 | T1 { f1 :: Int }
+	 | T2 T
+	deriving( Show, Read )
+
+main = print (read "3 :%% T2 T1 { f1=3 }" :: T)
+
+{- Here's the parser that is produced 
+
+import GHC.Read
+import Text.ParserCombinators.ReadPrec
+import Text.Read
+
+instance Read T where
+  readPrec =
+    parens
+    ( prec 4 (
+        do x           <- step readPrec
+           Symbol ":%%" <- lexP
+           y           <- step readPrec
+           return (x :%% y))
+      +++
+      prec (appPrec+1) (
+	do Ident "T1" <- lexP
+	   Punc "{" <- lexP
+	   Ident "f1" <- lexP
+	   Punc "=" <- lexP
+	   x	      <- reset readPrec
+	   Punc "}" <- lexP
+	   return (T1 { f1 = x }))
+      +++
+      prec appPrec (
+        do Ident "T2" <- lexP
+           x          <- step readPrec
+           return (T2 x))
+    )
+
+appPrec = 10::Int
+-}