Add a test highlighting a messy case for FFI type errors

3 files changed, 27 insertions, 0 deletions

diff --git a/testsuite/tests/ffi/should_fail/all.T b/testsuite/tests/ffi/should_fail/all.T
index 4793379fb4..abba1b5f6f 100644
--- a/testsuite/tests/ffi/should_fail/all.T
+++ b/testsuite/tests/ffi/should_fail/all.T
@@ -7,3 +7,4 @@ test('ccfail002', only_compiler_types(['ghc']), compile_fail, [''])
 test('ccfail003', only_compiler_types(['ghc']), compile_fail, [''])
 test('T3066', only_compiler_types(['ghc']), compile_fail, [''])
 test('ccfail004', only_compiler_types(['ghc']), multimod_compile_fail, ['ccfail004', '-v0'])
+test('ccfail005', only_compiler_types(['ghc']), compile_fail, [''])
diff --git a/testsuite/tests/ffi/should_fail/ccfail005.hs b/testsuite/tests/ffi/should_fail/ccfail005.hs
new file mode 100644
index 0000000000..3ba29a6d4c
--- /dev/null
+++ b/testsuite/tests/ffi/should_fail/ccfail005.hs
@@ -0,0 +1,16 @@
+
+{-# LANGUAGE TypeFamilies #-}
+
+module Ccfail005 where
+
+type family F a
+type instance F Bool = D -> IO Int
+type instance F Char = Int -> IO D
+data D = D
+
+-- These should be rejected as D isn't a type we can use with the FFI.
+-- Note that, in the signature the user writes, there aren't an
+-- "argument type" and "result type" to complain about, though.
+foreign import ccall f1 :: F Bool
+foreign import ccall f2 :: F Char
+
diff --git a/testsuite/tests/ffi/should_fail/ccfail005.stderr b/testsuite/tests/ffi/should_fail/ccfail005.stderr
new file mode 100644
index 0000000000..0d96fe91e3
--- /dev/null
+++ b/testsuite/tests/ffi/should_fail/ccfail005.stderr
@@ -0,0 +1,10 @@
+
+ccfail005.hs:14:1:
+    Unacceptable argument type in foreign declaration: D
+    When checking declaration:
+      foreign import ccall safe "static f1" f1 :: F Bool
+
+ccfail005.hs:15:1:
+    Unacceptable result type in foreign declaration: IO D
+    When checking declaration:
+      foreign import ccall safe "static f2" f2 :: F Char