Add test case for #12689

which test a few variants of rules involving constructors, including
nullary constructors, constructors with wrappers, and unsaturated of
constructors.

At the moment, all the rules work as expected, despite GHC’s compile
time warnings when called with -Wall.

testsuite/tests/simplCore/should_run/T12689.hs

@@ -0,0 +1,26 @@
+data T1 = MkT1Bad                     | MkT1Good                     deriving Show
+data T2 = MkT2Bad Int                 | MkT2Good Int                 deriving Show
+data T3 = MkT3Bad {-# UNPACK #-} !Int | MkT3Good {-# UNPACK #-} !Int deriving Show
+data T4 = MkT4Bad Int                 | MkT4Good Int                 deriving Show
+data T5 = MkT5Bad {-# UNPACK #-} !Int | MkT5Good {-# UNPACK #-} !Int deriving Show
+
+{-# RULES
+
+"T1"           MkT1Bad   = MkT1Good
+"T2" forall x. MkT2Bad x = MkT2Good x
+"T3" forall x. MkT3Bad x = MkT3Good x
+"T4"           MkT4Bad   = MkT4Good
+"T5"           MkT5Bad   = MkT5Good
+  #-}
+
+app = id
+{-# NOINLINE app #-}
+
+main = do
+  print MkT1Bad
+  print (MkT2Bad 42)
+  print (MkT3Bad 42)
+  print (MkT4Bad 42)
+  print (app MkT4Bad 42)
+  print (MkT5Bad 42)
+  print (app MkT5Bad 42)

testsuite/tests/simplCore/should_run/T12689.stdout

@@ -0,0 +1,7 @@
+MkT1Good
+MkT2Good 42
+MkT3Good 42
+MkT4Good 42
+MkT4Good 42
+MkT5Good 42
+MkT5Good 42

testsuite/tests/simplCore/should_run/T12689a.hs

@@ -0,0 +1,24 @@
+data T1 = MkT1Bad                     | MkT1Good                     deriving Show
+data T2 = MkT2Bad Int                 | MkT2Good Int                 deriving Show
+data T3 = MkT3Bad {-# UNPACK #-} !Int | MkT3Good {-# UNPACK #-} !Int deriving Show
+data T4 = MkT4Bad Int                 | MkT4Good Int                 deriving Show
+data T5 = MkT5Bad {-# UNPACK #-} !Int | MkT5Good {-# UNPACK #-} !Int deriving Show
+
+{-# RULES
+
+"T1"           app MkT1Bad     = MkT1Good
+"T2" forall x. app (MkT2Bad x) = MkT2Good x
+"T3" forall x. app (MkT3Bad x) = MkT3Good x
+"T4"           app MkT4Bad     = MkT4Good
+"T5"           app MkT5Bad     = MkT5Good
+  #-}
+
+app = id
+{-# NOINLINE app #-}
+
+main = do
+  print (app MkT1Bad)
+  print (app (MkT2Bad 42))
+  print (app (MkT3Bad 42))
+  print (app MkT4Bad 42)
+  print (app MkT5Bad 42)

testsuite/tests/simplCore/should_run/T12689a.stdout

@@ -0,0 +1,5 @@
+MkT1Good
+MkT2Good 42
+MkT3Good 42
+MkT4Good 42
+MkT5Good 42

testsuite/tests/simplCore/should_run/all.T

@@ -73,3 +73,5 @@ test('T10830', extra_run_opts('+RTS -K100k -RTS'), compile_and_run, [''])
 test('T11172', normal, compile_and_run, [''])
 test('T11731', normal, compile_and_run, ['-fspec-constr'])
 test('T7611', normal, compile_and_run, [''])
+test('T12689', normal, compile_and_run, [''])
+test('T12689a', normal, compile_and_run, [''])