#13031: Bogus calculation of bottoming arity
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Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 8.0.1
Keywords: | Operating System: Unknown/Multiple
Architecture: | Type of failure: None/Unknown
Unknown/Multiple |
Test Case: | Blocked By:
Blocking: | Related Tickets:
Differential Rev(s): | Wiki Page:
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In `CoreArity` we see
{{{
andArityType (ABot n1) (ABot n2) = ABot (n1 `min` n2)
}}}
If you look at the documentation for `ABot` (which is about functions that
are ''guaranteed'' to diverge) this is obviously bogus. The `min` should
be `max`!
Here's a test case:
{{{
{-# LANGUAGE MagicHash #-}
module Foo( f ) where
import GHC.Prim
f True = raise# True
f False = \p q -> raise# False
}}}
If you compile (with GHC 8.0) `-ddump-simpl` you'll see
{{{
f :: forall a p1 p2. Bool -> p2 -> p1 -> a
[GblId, Arity=1, Caf=NoCafRefs, Str=