Fix test T2497 to avoid infinite loop in RULES

testsuite/tests/typecheck/should_compile/T2497.hs

@@ -14,9 +14,13 @@ foo x = x
 -- Trac #2213; eq should not be reported as unused
 
 eq,beq :: Eq a => a -> a -> Bool
+{-# NOINLINE [0] eq #-}
+-- The pragma and [~1] in the RULE are to prevent an infinite loo
+-- in the simplifier, where the RULE fires infinitely in its
+-- own RHS
 eq = (==)    -- Used
 beq = (==)   -- Unused
 
 {-# RULES
-    "rule 1" forall x y. x == y = y `eq` x
+    "rule 1" [~1] forall x y. x == y = y `eq` x
   #-}

testsuite/tests/typecheck/should_compile/T2497.stderr

 
-T2497.hs:18:1: Warning: Defined but not used: ‘beq’
+T2497.hs:22:1: warning: Defined but not used: ‘beq’