diff options
| -rw-r--r-- | compiler/typecheck/TcUnify.lhs | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs index 169cf7b5c4..1868ad0d12 100644 --- a/compiler/typecheck/TcUnify.lhs +++ b/compiler/typecheck/TcUnify.lhs @@ -682,7 +682,13 @@ tc_sub1 sub_ctxt act_sty actual_ty exp_ib exp_sty expected_ty ; co_fn2 <- tc_sub sub_ctxt tau' tau' exp_ib exp_sty expected_ty -- Deal with the dictionaries - ; co_fn1 <- instCall InstSigOrigin inst_tys (substTheta subst' theta) + -- The origin gives a helpful origin when we have + -- a function with type f :: Int -> forall a. Num a => ... + -- This way the (Num a) dictionary gets an OccurrenceOf f origin + ; let orig = case sub_ctxt of + SubFun n -> OccurrenceOf n + other -> InstSigOrigin -- Unhelpful + ; co_fn1 <- instCall orig inst_tys (substTheta subst' theta) ; return (co_fn2 <.> co_fn1) } ----------------------------------- |