diff options
Diffstat (limited to 'compiler/GHC/Tc/Solver.hs')
| -rw-r--r-- | compiler/GHC/Tc/Solver.hs | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/compiler/GHC/Tc/Solver.hs b/compiler/GHC/Tc/Solver.hs index 134b230c06..d4a739a7ae 100644 --- a/compiler/GHC/Tc/Solver.hs +++ b/compiler/GHC/Tc/Solver.hs @@ -2421,14 +2421,24 @@ floatEqualities skols given_ids ev_binds_var no_given_eqs -- Identify which equalities are candidates for floating -- Float out alpha ~ ty, or ty ~ alpha which might be unified outside -- See Note [Which equalities to float] - is_float_eq_candidate ct - | pred <- ctPred ct - , EqPred NomEq ty1 ty2 <- classifyPredType pred + is_float_eq_candidate ct = float_help (classifyPredType (ctPred ct)) + + term_ev_allowed = termEvidenceAllowed ev_binds_var + + float_help (EqPred {}) | not term_ev_allowed = True + -- If term evidence is not allowed, try floating any + -- equality (both NomEq and ReprEq) in the hope that it + -- may be soluble higher up, where term evidence is allowed + -- See #18213 + + float_help (EqPred NomEq ty1 ty2) + -- NomEq only; ReprEq doesn't cause unification = case (tcGetTyVar_maybe ty1, tcGetTyVar_maybe ty2) of (Just tv1, _) -> float_tv_eq_candidate tv1 ty2 (_, Just tv2) -> float_tv_eq_candidate tv2 ty1 _ -> False - | otherwise = False + + float_help _ = False float_tv_eq_candidate tv1 ty2 -- See Note [Which equalities to float] = isMetaTyVar tv1 |