Add test case for #17186.

This got fixed sometime recently; not worth it trying to
figure out which commit.

2 files changed, 18 insertions, 1 deletions

diff --git a/testsuite/tests/typecheck/should_compile/T17186.hs b/testsuite/tests/typecheck/should_compile/T17186.hs
new file mode 100644
index 0000000000..c060f0b6f7
--- /dev/null
+++ b/testsuite/tests/typecheck/should_compile/T17186.hs
@@ -0,0 +1,17 @@
+{-# LANGUAGE DataKinds              #-}
+{-# LANGUAGE FlexibleContexts       #-}
+{-# LANGUAGE PolyKinds              #-}
+{-# LANGUAGE TypeFamilyDependencies #-}
+{-# LANGUAGE TypeOperators, AllowAmbiguousTypes          #-}
+
+module T17186 where
+
+-- This test is significantly abbreviated from what was posted; see
+-- #16512 for more context.
+
+type family Dim v
+
+type family v `OfDim` (n :: Dim v) = r | r -> n
+
+(!*^) :: Dim m `OfDim` j -> Dim m `OfDim` i
+(!*^) = undefined
diff --git a/testsuite/tests/typecheck/should_compile/all.T b/testsuite/tests/typecheck/should_compile/all.T
index d02c3ee2fa..263ff97ba1 100644
--- a/testsuite/tests/typecheck/should_compile/all.T
+++ b/testsuite/tests/typecheck/should_compile/all.T
@@ -728,4 +728,4 @@ test('T18831', normal, compile, [''])
 test('T18920', normal, compile, [''])
 test('T15942', normal, compile, [''])
 test('ClassDefaultInHsBoot', [extra_files(['ClassDefaultInHsBootA1.hs','ClassDefaultInHsBootA2.hs','ClassDefaultInHsBootA2.hs-boot','ClassDefaultInHsBootA3.hs'])], multimod_compile, ['ClassDefaultInHsBoot', '-v0'])
-
+test('T17186', normal, compile, [''])