diff options
Diffstat (limited to 'compiler/GHC/Hs/Binds.hs')
| -rw-r--r-- | compiler/GHC/Hs/Binds.hs | 33 |
1 files changed, 25 insertions, 8 deletions
diff --git a/compiler/GHC/Hs/Binds.hs b/compiler/GHC/Hs/Binds.hs index a1b72b914c..987631dc82 100644 --- a/compiler/GHC/Hs/Binds.hs +++ b/compiler/GHC/Hs/Binds.hs @@ -89,11 +89,28 @@ type instance XXValBindsLR (GhcPass pL) (GhcPass pR) -- --------------------------------------------------------------------- type instance XFunBind (GhcPass pL) GhcPs = NoExtField -type instance XFunBind (GhcPass pL) GhcRn = NameSet -- Free variables -type instance XFunBind (GhcPass pL) GhcTc = HsWrapper -- See comments on FunBind.fun_ext +type instance XFunBind (GhcPass pL) GhcRn = NameSet + -- ^ After the renamer (but before the type-checker), the FunBind + -- extension field contains the locally-bound free variables of this + -- defn. See Note [Bind free vars] +type instance XFunBind (GhcPass pL) GhcTc = HsWrapper + -- ^ After the type-checker, the FunBind extension field contains a + -- coercion from the type of the MatchGroup to the type of the Id. + -- Example: + -- + -- @ + -- f :: Int -> forall a. a -> a + -- f x y = y + -- @ + -- + -- Then the MatchGroup will have type (Int -> a' -> a') + -- (with a free type variable a'). The coercion will take + -- a CoreExpr of this type and convert it to a CoreExpr of + -- type Int -> forall a'. a' -> a' + -- Notice that the coercion captures the free a'. type instance XPatBind GhcPs (GhcPass pR) = EpAnn [AddEpAnn] -type instance XPatBind GhcRn (GhcPass pR) = NameSet -- Free variables +type instance XPatBind GhcRn (GhcPass pR) = NameSet -- ^ See Note [Bind free vars] type instance XPatBind GhcTc (GhcPass pR) = Type -- Type of the GRHSs type instance XVarBind (GhcPass pL) (GhcPass pR) = NoExtField @@ -105,7 +122,7 @@ type instance XABE (GhcPass p) = NoExtField type instance XXABExport (GhcPass p) = DataConCantHappen type instance XPSB (GhcPass idL) GhcPs = EpAnn [AddEpAnn] -type instance XPSB (GhcPass idL) GhcRn = NameSet +type instance XPSB (GhcPass idL) GhcRn = NameSet -- ^ Post renaming, FVs. See Note [Bind free vars] type instance XPSB (GhcPass idL) GhcTc = NameSet type instance XXPatSynBind (GhcPass idL) (GhcPass idR) = DataConCantHappen @@ -319,8 +336,8 @@ variables. The action happens in GHC.Tc.Gen.Bind.mkExport. Note [Bind free vars] ~~~~~~~~~~~~~~~~~~~~~ -The bind_fvs field of FunBind and PatBind records the free variables -of the definition. It is used for the following purposes +The extension fields of FunBind, PatBind and PatSynBind at GhcRn records the free +variables of the definition. It is used for the following purposes: a) Dependency analysis prior to type checking (see GHC.Tc.Gen.Bind.tc_group) @@ -334,10 +351,10 @@ c) Deciding whether the binding can be used in static forms Specifically, - * bind_fvs includes all free vars that are defined in this module + * it includes all free vars that are defined in this module (including top-level things and lexically scoped type variables) - * bind_fvs excludes imported vars; this is just to keep the set smaller + * it excludes imported vars; this is just to keep the set smaller * Before renaming, and after typechecking, the field is unused; it's just an error thunk |