diff options
| -rw-r--r-- | compiler/deSugar/DsBinds.hs | 5 | ||||
| -rw-r--r-- | compiler/typecheck/TcRnTypes.hs | 12 |
2 files changed, 12 insertions, 5 deletions
diff --git a/compiler/deSugar/DsBinds.hs b/compiler/deSugar/DsBinds.hs index db7acfd51c..6524e102d2 100644 --- a/compiler/deSugar/DsBinds.hs +++ b/compiler/deSugar/DsBinds.hs @@ -184,8 +184,9 @@ dsHsBind dflags (AbsBinds { abs_tvs = tyvars, abs_ev_vars = dicts , abs_binds = binds, abs_sig = has_sig }) = do { ds_binds <- addDictsDs (listToBag dicts) $ dsLHsBinds binds - -- addDictsDs: push type constraints deeper - -- for inner pattern match check + -- addDictsDs: push type constraints deeper + -- for inner pattern match check + -- See Check, Note [Type and Term Equality Propagation] ; ds_ev_binds <- dsTcEvBinds_s ev_binds diff --git a/compiler/typecheck/TcRnTypes.hs b/compiler/typecheck/TcRnTypes.hs index e8f0762d94..6627c25464 100644 --- a/compiler/typecheck/TcRnTypes.hs +++ b/compiler/typecheck/TcRnTypes.hs @@ -385,9 +385,15 @@ instance ContainsModule DsGblEnv where data DsLclEnv = DsLclEnv { dsl_meta :: DsMetaEnv, -- Template Haskell bindings dsl_loc :: RealSrcSpan, -- To put in pattern-matching error msgs - dsl_dicts :: Bag EvVar, -- Constraints from GADT pattern-matching - dsl_tm_cs :: Bag SimpleEq, - dsl_pm_iter :: IORef Int -- no iterations for pmcheck + + -- See Note [Note [Type and Term Equality Propagation] in Check.hs + -- These two fields are augmented as we walk inwards, + -- through each patttern match in turn + dsl_dicts :: Bag EvVar, -- Constraints from GADT pattern-matching + dsl_tm_cs :: Bag SimpleEq, -- Constraints form term-level pattern matching + + dsl_pm_iter :: IORef Int -- Number of iterations for pmcheck so far + -- We fail if this gets too big } -- Inside [| |] brackets, the desugarer looks |