Commit 3ae23992 authored by Simon Peyton Jones's avatar Simon Peyton Jones Committed by Marge Bot

Comments and tiny refactor

* Added Note [Quantified varaibles in partial type signatures]
  in TcRnTypes

* Kill dVarSetElemsWellScoped; it was only called in
  one function, quantifyTyVars.  I inlined it because it
  was only scopedSort . dVarSetElems

* Kill Type.tyCoVarsOfBindersWellScoped, never called.
parent 48fb3482
......@@ -1433,9 +1433,9 @@ quantifyTyVars gbl_tvs
-- NB: All variables in the kind of a covar must not be
-- quantified over, as we don't quantify over the covar.
dep_kvs = dVarSetElemsWellScoped $
dep_kvs = scopedSort $ dVarSetElems $
dep_tkvs `dVarSetMinusVarSet` mono_tvs
-- dVarSetElemsWellScoped: put the kind variables into
-- scopedSort: put the kind variables into
-- well-scoped order.
-- E.g. [k, (a::k)] not the other way roud
......@@ -1453,7 +1453,7 @@ quantifyTyVars gbl_tvs
-- This block uses level numbers to decide what to quantify
-- and emits a warning if the two methods do not give the same answer
; let dep_kvs2 = dVarSetElemsWellScoped $
; let dep_kvs2 = scopedSort $ dVarSetElems $
filterDVarSet (quantifiableTv outer_tclvl) dep_tkvs
nondep_tvs2 = filter (quantifiableTv outer_tclvl) $
dVarSetElems (nondep_tkvs `minusDVarSet` dep_tkvs)
......
......@@ -1542,6 +1542,10 @@ data TcIdSigInst
-- No need to keep track of whether they are truly lexically
-- scoped because the renamer has named them uniquely
-- See Note [Binding scoped type variables] in TcSigs
--
-- NB: The order of sig_inst_skols is irrelevant
-- for a CompleteSig, but for a PartialSig see
-- Note [Quantified varaibles in partial type signatures]
, sig_inst_theta :: TcThetaType
-- Instantiated theta. In the case of a
......@@ -1553,9 +1557,9 @@ data TcIdSigInst
-- Relevant for partial signature only
, sig_inst_wcs :: [(Name, TcTyVar)]
-- Like sig_inst_skols, but for wildcards. The named
-- wildcards scope over the binding, and hence their
-- Names may appear in type signatures in the binding
-- Like sig_inst_skols, but for /named/ wildcards (_a etc).
-- The named wildcards scope over the binding, and hence
-- their Names may appear in type signatures in the binding
, sig_inst_wcx :: Maybe TcType
-- Extra-constraints wildcard to fill in, if any
......@@ -1572,6 +1576,26 @@ if the original function had a signature like
But that's ok: tcMatchesFun (called by tcRhs) can deal with that
It happens, too! See Note [Polymorphic methods] in TcClassDcl.
Note [Quantified varaibles in partial type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
f :: forall a b. _ -> a -> _ -> b
f (x,y) p q = q
Then we expect f's final type to be
f :: forall {x,y}. forall a b. (x,y) -> a -> b -> b
Note that x,y are Inferred, and can't be use for visible type
application (VTA). But a,b are Specified, and remain Specified
in the final type, so we can use VTA for them. (Exception: if
it turns out that a's kind mentions b we need to reorder them
with scopedSort.)
The sig_inst_skols of the TISI from a partial signature records
that original order, and is used to get the variables of f's
final type in the correct order.
Note [Wildcards in partial signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The wildcards in psig_wcs may stand for a type mentioning
......
......@@ -158,8 +158,8 @@ module Type (
typeSize, occCheckExpand,
-- * Well-scoped lists of variables
dVarSetElemsWellScoped, scopedSort, tyCoVarsOfTypeWellScoped,
tyCoVarsOfTypesWellScoped, tyCoVarsOfBindersWellScoped,
scopedSort, tyCoVarsOfTypeWellScoped,
tyCoVarsOfTypesWellScoped,
-- * Type comparison
eqType, eqTypeX, eqTypes, nonDetCmpType, nonDetCmpTypes, nonDetCmpTypeX,
......@@ -250,7 +250,7 @@ import UniqSet
import Class
import TyCon
import TysPrim
import {-# SOURCE #-} TysWiredIn ( listTyCon, typeNatKind, unitTy
import {-# SOURCE #-} TysWiredIn ( listTyCon, typeNatKind
, typeSymbolKind, liftedTypeKind
, constraintKind )
import PrelNames
......@@ -2199,15 +2199,6 @@ scopedSort = go [] []
-- lists not in correspondence
insert _ _ _ = panic "scopedSort"
-- | Extract a well-scoped list of variables from a deterministic set of
-- variables. The result is deterministic.
-- NB: There used to exist varSetElemsWellScoped :: VarSet -> [Var] which
-- took a non-deterministic set and produced a non-deterministic
-- well-scoped list. If you care about the list being well-scoped you also
-- most likely care about it being in deterministic order.
dVarSetElemsWellScoped :: DVarSet -> [Var]
dVarSetElemsWellScoped = scopedSort . dVarSetElems
-- | Get the free vars of a type in scoped order
tyCoVarsOfTypeWellScoped :: Type -> [TyVar]
tyCoVarsOfTypeWellScoped = scopedSort . tyCoVarsOfTypeList
......@@ -2216,12 +2207,6 @@ tyCoVarsOfTypeWellScoped = scopedSort . tyCoVarsOfTypeList
tyCoVarsOfTypesWellScoped :: [Type] -> [TyVar]
tyCoVarsOfTypesWellScoped = scopedSort . tyCoVarsOfTypesList
-- | Given the suffix of a telescope, returns the prefix.
-- Ex: given [(k :: j), (a :: Proxy k)], returns [(j :: *)].
tyCoVarsOfBindersWellScoped :: [TyVar] -> [TyVar]
tyCoVarsOfBindersWellScoped tvs
= tyCoVarsOfTypeWellScoped (mkInvForAllTys tvs unitTy)
------------- Closing over kinds -----------------
-- | Add the kind variables free in the kinds of the tyvars in the given set.
......
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