Commit fb9f8859 authored by simonpj@microsoft.com's avatar simonpj@microsoft.com

Add a (DEBUG-only) warning for top-level error thunks with uninformative strictness info

In the past I've seen this in an interface file

   foo = error "urk"

but *without* a bottoming strictness info on 'foo'. This WARN just 
checks (non-fatally) for the bad case, so that we can track it down easily
parent eeef817a
......@@ -18,7 +18,7 @@ import CoreFVs
import CoreTidy
import CoreMonad
import CoreUtils
import CoreArity ( exprArity )
import CoreArity ( exprArity, exprBotStrictness_maybe )
import Class ( classSelIds )
import VarEnv
import VarSet
......@@ -969,18 +969,27 @@ tidyTopPair :: Bool -- show unfolding
-- in the IdInfo of one early in the group
tidyTopPair show_unfold rhs_tidy_env caf_info name' (bndr, rhs)
= (bndr', rhs')
= WARN( not _bottom_exposed, ppr bndr1 )
(bndr1, rhs1)
where
bndr' = mkGlobalId details name' ty' idinfo'
-- If the cheap-and-cheerful bottom analyser can see that
-- the RHS is bottom, it should jolly well be exposed
_bottom_exposed = case exprBotStrictness_maybe rhs of
Nothing -> True
Just (arity, _) -> appIsBottom str arity
where
str = newStrictnessInfo idinfo `orElse` topSig
bndr1 = mkGlobalId details name' ty' idinfo'
details = idDetails bndr -- Preserve the IdDetails
ty' = tidyTopType (idType bndr)
rhs' = tidyExpr rhs_tidy_env rhs
rhs1 = tidyExpr rhs_tidy_env rhs
idinfo = idInfo bndr
idinfo' = tidyTopIdInfo (isExternalName name')
idinfo unfold_info
arity caf_info
unfold_info | show_unfold = tidyUnfolding rhs_tidy_env rhs' (unfoldingInfo idinfo)
unfold_info | show_unfold = tidyUnfolding rhs_tidy_env rhs1 (unfoldingInfo idinfo)
| otherwise = noUnfolding
-- NB: do *not* expose the worker if show_unfold is off,
-- because that means this thing is a loop breaker or
......
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