diff options
| author | Vladislav Zavialov <vlad.z.4096@gmail.com> | 2018-06-16 23:44:39 -0400 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2018-06-16 23:44:57 -0400 |
| commit | 8df24474d0194d28b8273c1539af05793156e23f (patch) | |
| tree | eeeaf190edb831e45fb23af1960213b530637794 /compiler/rename | |
| parent | 4cd552184cbc5bed33da21497537df4e400a1a2f (diff) | |
| download | haskell-8df24474d0194d28b8273c1539af05793156e23f.tar.gz | |
Warn about implicit kind variables with -Wcompat
According to an accepted proposal
https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/002
4-no-kind-vars.rst
With -Wcompat, warn if a kind variable is brought into scope
implicitly in a type with an explicit forall. This applies to type
signatures and to other contexts that allow a forall with the
forall-or-nothing rule in effect (for example, class instances).
Test Plan: Validate
Reviewers: goldfire, hvr, bgamari, RyanGlScott
Reviewed By: goldfire
Subscribers: RyanGlScott, rwbarton, thomie, carter
GHC Trac Issues: #15264
Differential Revision: https://phabricator.haskell.org/D4834
Diffstat (limited to 'compiler/rename')
| -rw-r--r-- | compiler/rename/RnTypes.hs | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/compiler/rename/RnTypes.hs b/compiler/rename/RnTypes.hs index 3d60a9f6c3..ca4986f050 100644 --- a/compiler/rename/RnTypes.hs +++ b/compiler/rename/RnTypes.hs @@ -334,6 +334,11 @@ rnImplicitBndrs bind_free_tvs ; traceRn "rnImplicitBndrs" (vcat [ ppr kvs, ppr tvs, ppr real_tvs ]) + ; whenWOptM Opt_WarnImplicitKindVars $ + unless (bind_free_tvs || null kvs) $ + addWarnAt (Reason Opt_WarnImplicitKindVars) (getLoc (head kvs)) $ + implicit_kind_vars_msg kvs + ; loc <- getSrcSpanM ; vars <- mapM (newLocalBndrRn . L loc . unLoc) (kvs ++ real_tvs) @@ -343,6 +348,16 @@ rnImplicitBndrs bind_free_tvs ; bindLocalNamesFV vars $ thing_inside vars } + where + implicit_kind_vars_msg kvs = + vcat [ text "An explicit" <+> quotes (text "forall") <+> + text "was used, but the following kind variables" <+> + text "are not quantified:" <+> + hsep (punctuate comma (map (quotes . ppr) kvs)) + , text "Despite this fact, GHC will introduce them into scope," <+> + text "but it will stop doing so in the future." + , text "Suggested fix: add" <+> + quotes (text "forall" <+> hsep (map ppr kvs) <> char '.') ] rnLHsInstType :: SDoc -> LHsSigType GhcPs -> RnM (LHsSigType GhcRn, FreeVars) -- Rename the type in an instance. |