diff options
Diffstat (limited to 'compiler/GHC/Tc/Solver/Monad.hs')
| -rw-r--r-- | compiler/GHC/Tc/Solver/Monad.hs | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/compiler/GHC/Tc/Solver/Monad.hs b/compiler/GHC/Tc/Solver/Monad.hs index f3d0097f93..49699d865d 100644 --- a/compiler/GHC/Tc/Solver/Monad.hs +++ b/compiler/GHC/Tc/Solver/Monad.hs @@ -2119,14 +2119,17 @@ checkTouchableTyVarEq ev lhs_tv rhs ; if not (cterHasNoProblem reason) -- Failed to promote free vars then failCheckWith reason else - do { let tv_info | isConcreteInfo lhs_tv_info = lhs_tv_info - | otherwise = TauTv - -- Make a concrete tyvar if lhs_tv is concrete - -- e.g. alpha[2,conc] ~ Maybe (F beta[4]) - -- We want to flatten to - -- alpha[2,conc] ~ Maybe gamma[2,conc] - -- gamma[2,conc] ~ F beta[4] - ; new_tv_ty <- TcM.newMetaTyVarTyWithInfo lhs_tv_lvl tv_info fam_app_kind + do { new_tv_ty <- + case lhs_tv_info of + ConcreteTv conc_info -> + -- Make a concrete tyvar if lhs_tv is concrete + -- e.g. alpha[2,conc] ~ Maybe (F beta[4]) + -- We want to flatten to + -- alpha[2,conc] ~ Maybe gamma[2,conc] + -- gamma[2,conc] ~ F beta[4] + TcM.newConcreteTyVarTyAtLevel conc_info lhs_tv_lvl fam_app_kind + _ -> TcM.newMetaTyVarTyAtLevel lhs_tv_lvl fam_app_kind + ; let pty = mkPrimEqPredRole Nominal fam_app new_tv_ty ; hole <- TcM.newCoercionHole pty ; let new_ev = CtWanted { ctev_pred = pty |