diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/typecheck/TcInstDcls.hs | 9 | ||||
| -rw-r--r-- | compiler/typecheck/TcTyClsDecls.hs | 18 |
2 files changed, 22 insertions, 5 deletions
diff --git a/compiler/typecheck/TcInstDcls.hs b/compiler/typecheck/TcInstDcls.hs index b8eb17fb57..8d2ef94453 100644 --- a/compiler/typecheck/TcInstDcls.hs +++ b/compiler/typecheck/TcInstDcls.hs @@ -799,7 +799,12 @@ tcDataFamHeader mb_clsinfo fam_tc imp_vars mb_bndrs fixity hs_ctxt hs_pats m_ksi ; lhs_ty <- checkExpectedKindX pp_lhs lhs_ty lhs_kind res_kind ; return (stupid_theta, lhs_ty, res_kind) } - -- See Note [Generalising in tcFamTyPatsAndThen] + -- See TcTyClsDecls Note [Generalising in tcFamTyPatsGuts] + -- This code (and the stuff immediately above) is very similar + -- to that in tcFamTyInstEqnGuts. Maybe we should abstract the + -- common code; but for the moment I concluded that it's + -- clearer to duplicate it. Still, if you fix a bug here, + -- check there too! ; let scoped_tvs = imp_tvs ++ exp_tvs ; dvs <- candidateQTyVarsOfTypes (lhs_ty : mkTyVarTys scoped_tvs) ; qtvs <- quantifyTyVars emptyVarSet dvs @@ -901,7 +906,7 @@ There are several fiddly subtleties lurking here data family X a :: forall k. * -> * -- Note: a forall that is not used data instance X Int b = MkX - So the data intance is really + So the data instance is really data istance X Int @k b = MkX The axiom will look like diff --git a/compiler/typecheck/TcTyClsDecls.hs b/compiler/typecheck/TcTyClsDecls.hs index eda86f9277..ce7cc83858 100644 --- a/compiler/typecheck/TcTyClsDecls.hs +++ b/compiler/typecheck/TcTyClsDecls.hs @@ -1817,8 +1817,8 @@ indexed-types/should_compile/T12369 for an example. So, the kind-checker must return the new skolems and args (that is, Type or (Type -> Type) for the equations above) and the instantiated kind. -Note [Generalising in tcFamTyPatsAndThen] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Note [Generalising in tcFamTyPatsGuts] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Suppose we have something like type instance forall (a::k) b. F t1 t2 = rhs @@ -1872,7 +1872,12 @@ tcTyFamInstEqnGuts fam_tc mb_clsinfo imp_vars exp_bndrs hs_pats hs_rhs_ty ; rhs_ty <- tcCheckLHsType hs_rhs_ty rhs_kind ; return (lhs_ty, rhs_ty) } - -- See Note [Generalising in tcFamTyPatsAndThen] + -- See Note [Generalising in tcFamTyPatsGuts] + -- This code (and the stuff immediately above) is very similar + -- to that in tcDataFamHeader. Maybe we should abstract the + -- common code; but for the moment I concluded that it's + -- clearer to duplicate it. Still, if you fix a bug here, + -- check there too! ; let scoped_tvs = imp_tvs ++ exp_tvs ; dvs <- candidateQTyVarsOfTypes (lhs_ty : mkTyVarTys scoped_tvs) ; qtvs <- quantifyTyVars emptyVarSet dvs @@ -1882,6 +1887,9 @@ tcTyFamInstEqnGuts fam_tc mb_clsinfo imp_vars exp_bndrs hs_pats hs_rhs_ty ; rhs_ty <- zonkTcTypeToTypeX ze rhs_ty ; let pats = unravelFamInstPats lhs_ty + -- Note that we do this after solveEqualities + -- so that any strange coercions inside lhs_ty + -- have been solved before we attempt to unravel it ; traceTc "tcTyFamInstEqnGuts }" (ppr fam_tc <+> pprTyVars qtvs) ; return (qtvs, pats, rhs_ty) } where @@ -1963,6 +1971,10 @@ unravelFamInstPats fam_app = case splitTyConApp_maybe fam_app of Just (_, pats) -> pats Nothing -> WARN( True, bad_lhs fam_app ) [] + -- The Nothing case cannot happen for type families, because + -- we don't call unravelFamInstPats until we've solved the + -- equalities. For data families I wasn't quite as convinced + -- so I've let it as a warning rather than a panic. where bad_lhs fam_app = hang (text "Ill-typed LHS of family instance") |