Add new testcase for Trac #7560.

testsuite/tests/indexed-types/should_fail/T7560.hs

+{-# LANGUAGE TypeFamilies #-}
+
+module T7560 where
+
+type family F a
+
+type instance where
+  F Int = Int
+  F Bool = Bool
+
+type instance where
+  F Int = Char
+  F Double = Double
\ No newline at end of file

testsuite/tests/indexed-types/should_fail/T7560.stderr

+
+T7560.hs:8:3:
+    Conflicting family instance declarations:
+      F Int -- Defined at T7560.hs:8:3
+      F Int -- Defined at T7560.hs:12:3

testsuite/tests/indexed-types/should_fail/all.T

@@ -94,3 +94,5 @@ test('T7354a',
      run_command,
      ['$MAKE -s --no-print-directory T7354a'])
 test('T7536', normal, compile_fail, [''])
+
+test('T7560', normal, compile_fail, [''])
\ No newline at end of file