Add test for #20894

2 files changed, 25 insertions, 0 deletions

diff --git a/testsuite/tests/simplCore/should_compile/T20894.hs b/testsuite/tests/simplCore/should_compile/T20894.hs
new file mode 100644
index 0000000000..d8ae7a3b99
--- /dev/null
+++ b/testsuite/tests/simplCore/should_compile/T20894.hs
@@ -0,0 +1,23 @@
+{-# LANGUAGE Haskell2010 #-}
+
+module T20894 where
+
+import Prelude (Int)
+
+data LitE = IntLit !Int | StringLit
+data Term = LitE LitE | Term :$ Term | S Term | VarE
+data Val = LitV LitE
+
+eval :: Term -> Val
+eval (LitE l)  = LitV l
+eval (S a) = eval a
+eval _ = LitV StringLit
+
+church :: Int -> Term
+church 0 = VarE
+church _ = S VarE
+
+evalChurchId :: Int -> Int -> Int
+evalChurchId i arg =
+  case eval (S (S (church i)) :$ LitE (IntLit arg) ) of
+    LitV (IntLit res) -> res
diff --git a/testsuite/tests/simplCore/should_compile/all.T b/testsuite/tests/simplCore/should_compile/all.T
index d500b5364a..7285b91c45 100644
--- a/testsuite/tests/simplCore/should_compile/all.T
+++ b/testsuite/tests/simplCore/should_compile/all.T
@@ -377,3 +377,5 @@ test('T20200a', normal, compile, ['-O2'])
 test('T20200b', normal, compile, ['-O2'])
 test('T20200KG', [extra_files(['T20200KGa.hs', 'T20200KG.hs-boot'])], multimod_compile, ['T20200KG', '-v0 -O2 -fspecialise-aggressively'])
 test('T20639', normal, compile, ['-O2'])
+
+test('T20894', normal, compile, ['-dcore-lint -O1 -ddebug-output'])