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It seems that in the current HEAD, the SPECIALISE pragma generates a rule with the same activation as the function that is being specialised which is utterly wrong. A small example:

foo :: Num a => a -> a
{-# NOINLINE foo #-}
foo x = x+1

{-# SPECIALISE foo :: Int -> Int #-}

The HEAD generates this rule which never fires:

"SPEC T.foo" [NEVER] forall $dNum :: GHC.Num.Num GHC.Types.Int
  T.foo @ GHC.Types.Int $dNum = T.foo_foo

If I change the NOINLINE pragma to INLINE [0], the rule will get the activation [0]. 7.2.2 behaves as expected:

"SPEC T.foo" [ALWAYS] forall $dNum :: GHC.Num.Num GHC.Types.Int
  T.foo @ GHC.Types.Int $dNum = T.foo_foo

I haven't checked 7.4 but if this happens there, too, then fixing it before the release would be great. I assume it's just a typo somewhere.

Trac metadata

Trac field	Value
Version	7.5
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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