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| author | Ryan Scott <ryan.gl.scott@gmail.com> | 2019-10-15 11:08:26 -0400 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-10-24 18:38:32 -0400 |
| commit | 9de3f8b1382f46899b2be2092c0b94eae95ae6aa (patch) | |
| tree | 0a863f2586a6164cd482e4697ec9a97e81a04d9e /compiler | |
| parent | 6824f29aebd28571db118eb6877ef04eda630871 (diff) | |
| download | haskell-9de3f8b1382f46899b2be2092c0b94eae95ae6aa.tar.gz | |
Make isTcLevPoly more conservative with newtypes (#17360)
`isTcLevPoly` gives an approximate answer for when a type constructor
is levity polymorphic when fully applied, where `True` means
"possibly levity polymorphic" and `False` means "definitely not
levity polymorphic". `isTcLevPoly` returned `False` for newtypes,
which is incorrect in the presence of `UnliftedNewtypes`, leading
to #17360. This patch tweaks `isTcLevPoly` to return `True` for
newtypes instead.
Fixes #17360.
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/iface/BuildTyCl.hs | 8 | ||||
| -rw-r--r-- | compiler/types/TyCon.hs | 21 |
2 files changed, 23 insertions, 6 deletions
diff --git a/compiler/iface/BuildTyCl.hs b/compiler/iface/BuildTyCl.hs index dc1c843889..827b89983f 100644 --- a/compiler/iface/BuildTyCl.hs +++ b/compiler/iface/BuildTyCl.hs @@ -54,12 +54,14 @@ mkNewTyConRhs tycon_name tycon con ; return (NewTyCon { data_con = con, nt_rhs = rhs_ty, nt_etad_rhs = (etad_tvs, etad_rhs), - nt_co = nt_ax } ) } + nt_co = nt_ax, + nt_lev_poly = isKindLevPoly res_kind } ) } -- Coreview looks through newtypes with a Nothing -- for nt_co, or uses explicit coercions otherwise where - tvs = tyConTyVars tycon - roles = tyConRoles tycon + tvs = tyConTyVars tycon + roles = tyConRoles tycon + res_kind = tyConResKind tycon con_arg_ty = case dataConRepArgTys con of [arg_ty] -> arg_ty tys -> pprPanic "mkNewTyConRhs" (ppr con <+> ppr tys) diff --git a/compiler/types/TyCon.hs b/compiler/types/TyCon.hs index 7af2bc0ad7..31bfddce81 100644 --- a/compiler/types/TyCon.hs +++ b/compiler/types/TyCon.hs @@ -992,7 +992,7 @@ data AlgTyConRhs -- shorter than the declared arity of the 'TyCon'. -- See Note [Newtype eta] - nt_co :: CoAxiom Unbranched + nt_co :: CoAxiom Unbranched, -- The axiom coercion that creates the @newtype@ -- from the representation 'Type'. @@ -1001,6 +1001,16 @@ data AlgTyConRhs -- See Note [Newtype eta] -- Watch out! If any newtypes become transparent -- again check #1072. + nt_lev_poly :: Bool + -- 'True' if the newtype can be levity polymorphic when + -- fully applied to its arguments, 'False' otherwise. + -- This can only ever be 'True' with UnliftedNewtypes. + -- + -- Invariant: nt_lev_poly nt = isTypeLevPoly (nt_rhs nt) + -- + -- This is cached to make it cheaper to check if a + -- variable binding is levity polymorphic, as used by + -- isTcLevPoly. } mkSumTyConRhs :: [DataCon] -> AlgTyConRhs @@ -2241,8 +2251,13 @@ setTcTyConKind tc _ = pprPanic "setTcTyConKind" (ppr tc) -- Precondition: The fully-applied TyCon has kind (TYPE blah) isTcLevPoly :: TyCon -> Bool isTcLevPoly FunTyCon{} = False -isTcLevPoly (AlgTyCon { algTcParent = UnboxedAlgTyCon _ }) = True -isTcLevPoly AlgTyCon{} = False +isTcLevPoly (AlgTyCon { algTcParent = parent, algTcRhs = rhs }) + | UnboxedAlgTyCon _ <- parent + = True + | NewTyCon { nt_lev_poly = lev_poly } <- rhs + = lev_poly -- Newtypes can be levity polymorphic with UnliftedNewtypes (#17360) + | otherwise + = False isTcLevPoly SynonymTyCon{} = True isTcLevPoly FamilyTyCon{} = True isTcLevPoly PrimTyCon{} = False |