From e07e383a3250cb27a9128ad8d5c68def5c3df336 Mon Sep 17 00:00:00 2001 From: Ryan Scott Date: Sun, 5 Jul 2020 16:15:01 -0400 Subject: Replace HsImplicitBndrs with HsOuterTyVarBndrs This refactors the GHC AST to remove `HsImplicitBndrs` and replace it with `HsOuterTyVarBndrs`, a type which records whether the outermost quantification in a type is explicit (i.e., with an outermost, invisible `forall`) or implicit. As a result of this refactoring, it is now evident in the AST where the `forall`-or-nothing rule applies: it's all the places that use `HsOuterTyVarBndrs`. See the revamped `Note [forall-or-nothing rule]` in `GHC.Hs.Type` (previously in `GHC.Rename.HsType`). Moreover, the places where `ScopedTypeVariables` brings lexically scoped type variables into scope are a subset of the places that adhere to the `forall`-or-nothing rule, so this also makes places that interact with `ScopedTypeVariables` easier to find. See the revamped `Note [Lexically scoped type variables]` in `GHC.Hs.Type` (previously in `GHC.Tc.Gen.Sig`). `HsOuterTyVarBndrs` are used in type signatures (see `HsOuterSigTyVarBndrs`) and type family equations (see `HsOuterFamEqnTyVarBndrs`). The main difference between the former and the latter is that the former cares about specificity but the latter does not. There are a number of knock-on consequences: * There is now a dedicated `HsSigType` type, which is the combination of `HsOuterSigTyVarBndrs` and `HsType`. `LHsSigType` is now an alias for an `XRec` of `HsSigType`. * Working out the details led us to a substantial refactoring of the handling of explicit (user-written) and implicit type-variable bindings in `GHC.Tc.Gen.HsType`. Instead of a confusing family of higher order functions, we now have a local data type, `SkolemInfo`, that controls how these binders are kind-checked. It remains very fiddly, not fully satisfying. But it's better than it was. Fixes #16762. Bumps the Haddock submodule. Co-authored-by: Simon Peyton Jones Co-authored-by: Richard Eisenberg Co-authored-by: Zubin Duggal --- compiler/GHC/Tc/TyCl/Class.hs | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) (limited to 'compiler/GHC/Tc/TyCl/Class.hs') diff --git a/compiler/GHC/Tc/TyCl/Class.hs b/compiler/GHC/Tc/TyCl/Class.hs index 92be85fa06..8e637a1a32 100644 --- a/compiler/GHC/Tc/TyCl/Class.hs +++ b/compiler/GHC/Tc/TyCl/Class.hs @@ -157,16 +157,14 @@ tcClassSigs clas sigs def_methods dm_bind_names :: [Name] -- These ones have a value binding in the class decl dm_bind_names = [op | L _ (FunBind {fun_id = L _ op}) <- bagToList def_methods] - skol_info = TyConSkol ClassFlavour clas - tc_sig :: NameEnv (SrcSpan, Type) -> ([Located Name], LHsSigType GhcRn) -> TcM [TcMethInfo] tc_sig gen_dm_env (op_names, op_hs_ty) = do { traceTc "ClsSig 1" (ppr op_names) - ; op_ty <- tcClassSigType skol_info op_names op_hs_ty + ; op_ty <- tcClassSigType op_names op_hs_ty -- Class tyvars already in scope - ; traceTc "ClsSig 2" (ppr op_names) + ; traceTc "ClsSig 2" (ppr op_names $$ ppr op_ty) ; return [ (op_name, op_ty, f op_name) | L _ op_name <- op_names ] } where f nm | Just lty <- lookupNameEnv gen_dm_env nm = Just (GenericDM lty) @@ -174,7 +172,7 @@ tcClassSigs clas sigs def_methods | otherwise = Nothing tc_gen_sig (op_names, gen_hs_ty) - = do { gen_op_ty <- tcClassSigType skol_info op_names gen_hs_ty + = do { gen_op_ty <- tcClassSigType op_names gen_hs_ty ; return [ (op_name, (loc, gen_op_ty)) | L loc op_name <- op_names ] } {- @@ -290,7 +288,7 @@ tcDefMeth clas tyvars this_dict binds_in hs_sig_fn prag_fn ; let local_dm_id = mkLocalId local_dm_name Many local_dm_ty local_dm_sig = CompleteSig { sig_bndr = local_dm_id , sig_ctxt = ctxt - , sig_loc = getLoc (hsSigType hs_ty) } + , sig_loc = getLoc hs_ty } ; (ev_binds, (tc_bind, _)) <- checkConstraints skol_info tyvars [this_dict] $ -- cgit v1.2.1