X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcSimplify.lhs;h=932cb68f425ba706a4114cbd1a1c2e3396a72c60;hp=9d89125dd48dab4b5f7f0bb66d3ea52b83f12e63;hb=e79c9ce01d0ce4412bd4bcd99c8c728a6a2ec569;hpb=c7344a639519b0ecd4ac24252ebc13ffdd3e9bd7 diff --git a/compiler/typecheck/TcSimplify.lhs b/compiler/typecheck/TcSimplify.lhs index 9d89125..932cb68 100644 --- a/compiler/typecheck/TcSimplify.lhs +++ b/compiler/typecheck/TcSimplify.lhs @@ -16,6 +16,8 @@ module TcSimplify ( tcSimplifyDeriv, tcSimplifyDefault, bindInstsOfLocalFuns, + + tcSimplifyStagedExpr, misMatchMsg ) where @@ -58,6 +60,7 @@ import Util import SrcLoc import DynFlags import FastString + import Control.Monad import Data.List \end{code} @@ -861,7 +864,7 @@ Note [NO TYVARS] The excitement comes when simplifying the bindings for h. Initially try to simplify {y @ [[t1]] t2, 0 @ t1}, with initial qtvs = {t2}. -From this we get t1:=:t2, but also various bindings. We can't forget +From this we get t1~t2, but also various bindings. We can't forget the bindings (because of [LOOP]), but in fact t1 is what g is polymorphic in. @@ -977,7 +980,7 @@ makeImplicationBind :: InstLoc -> [TcTyVar] -- (ir1, .., irn) = f qtvs givens -- where f is (evidence for) the new implication constraint -- f :: forall qtvs. givens => (ir1, .., irn) --- qtvs includes coercion variables. +-- qtvs includes coercion variables -- -- This binding must line up the 'rhs' in reduceImplication makeImplicationBind loc all_tvs @@ -997,7 +1000,7 @@ makeImplicationBind loc all_tvs name = mkInternalName uniq (mkVarOcc "ic") span implic_inst = ImplicInst { tci_name = name, tci_tyvars = all_tvs, - tci_given = (eq_givens ++ dict_givens), + tci_given = eq_givens ++ dict_givens, -- same order as binders tci_wanted = irreds, tci_loc = loc } @@ -1412,7 +1415,7 @@ tcSimplifyRestricted -- Used for restricted binding groups tcSimplifyRestricted doc top_lvl bndrs tau_tvs wanteds -- Zonk everything in sight = do { traceTc (text "tcSimplifyRestricted") - ; wanteds' <- zonkInsts wanteds + ; wanteds_z <- zonkInsts wanteds -- 'ReduceMe': Reduce as far as we can. Don't stop at -- dicts; the idea is to get rid of as many type @@ -1424,7 +1427,7 @@ tcSimplifyRestricted doc top_lvl bndrs tau_tvs wanteds -- HOWEVER, some unification may take place, if we instantiate -- a method Inst with an equality constraint ; let env = mkNoImproveRedEnv doc (\_ -> ReduceMe) - ; (_imp, _binds, constrained_dicts) <- reduceContext env wanteds' + ; (_imp, _binds, constrained_dicts) <- reduceContext env wanteds_z -- Next, figure out the tyvars we will quantify over ; tau_tvs' <- zonkTcTyVarsAndFV (varSetElems tau_tvs) @@ -1452,6 +1455,13 @@ tcSimplifyRestricted doc top_lvl bndrs tau_tvs wanteds ppr _binds, ppr constrained_tvs', ppr tau_tvs', ppr qtvs ]) + -- Zonk wanteds again! The first call to reduceContext may have + -- instantiated some variables. + -- FIXME: If red_improve would work, we could propagate that into + -- the equality solver, too, to prevent instantating any + -- variables. + ; wanteds_zz <- zonkInsts wanteds_z + -- The first step may have squashed more methods than -- necessary, so try again, this time more gently, knowing the exact -- set of type variables to quantify over. @@ -1473,7 +1483,7 @@ tcSimplifyRestricted doc top_lvl bndrs tau_tvs wanteds (is_nested_group || isDict inst) = Stop | otherwise = ReduceMe env = mkNoImproveRedEnv doc try_me - ; (_imp, binds, irreds) <- reduceContext env wanteds' + ; (_imp, binds, irreds) <- reduceContext env wanteds_zz -- See "Notes on implicit parameters, Question 4: top level" ; ASSERT( all (isFreeWrtTyVars qtvs) irreds ) -- None should be captured @@ -1883,9 +1893,13 @@ reduceContext env wanteds0 } -- Solve the *wanted* *dictionary* constraints (not implications) - -- This may expose some further equational constraints... + -- This may expose some further equational constraints in the course + -- of improvement due to functional dependencies if any of the + -- involved unifications gets deferred. ; let (wanted_implics, wanted_dicts) = partition isImplicInst wanteds' ; (avails, extra_eqs) <- getLIE (reduceList env wanted_dicts init_state) + -- The getLIE is reqd because reduceList does improvement + -- (via extendAvails) which may in turn do unification ; (dict_binds, bound_dicts, dict_irreds) <- extractResults avails wanted_dicts @@ -1911,22 +1925,24 @@ reduceContext env wanteds0 -- go round again. We do so in either of two cases: -- (1) If dictionary reduction or equality solving led to -- improvement (i.e., instantiated type variables). - -- (2) If we uncovered extra equalities. We will try to solve them - -- in the next iteration. - -- (3) If we reduced dictionaries (i.e., got dictionary bindings), + -- (2) If we reduced dictionaries (i.e., got dictionary bindings), -- they may have exposed further opportunities to normalise -- family applications. See Note [Dictionary Improvement] + -- + -- NB: We do *not* go around for new extra_eqs. Morally, we should, + -- but we can't without risking non-termination (see #2688). By + -- not going around, we miss some legal programs mixing FDs and + -- TFs, but we never claimed to support such programs in the + -- current implementation anyway. ; let all_irreds = dict_irreds ++ implic_irreds ++ extra_eqs avails_improved = availsImproved avails improvedFlexible = avails_improved || eq_improved - extraEqs = (not . null) extra_eqs reduced_dicts = not (isEmptyBag dict_binds) - improved = improvedFlexible || extraEqs || reduced_dicts + improved = improvedFlexible || reduced_dicts -- improvedHint = (if avails_improved then " [AVAILS]" else "") ++ - (if eq_improved then " [EQ]" else "") ++ - (if extraEqs then " [EXTRA EQS]" else "") + (if eq_improved then " [EQ]" else "") ; traceTc (text "reduceContext end" <+> (vcat [ text "----------------------", @@ -3001,6 +3017,26 @@ tcSimplifyDefault theta = do doc = ptext (sLit "default declaration") \end{code} +@tcSimplifyStagedExpr@ performs a simplification but does so at a new +stage. This is used when typechecking annotations and splices. + +\begin{code} + +tcSimplifyStagedExpr :: ThStage -> TcM a -> TcM (a, TcDictBinds) +-- Type check an expression that runs at a top level stage as if +-- it were going to be spliced and then simplify it +tcSimplifyStagedExpr stage tc_action + = setStage stage $ do { + -- Typecheck the expression + (thing', lie) <- getLIE tc_action + + -- Solve the constraints + ; const_binds <- tcSimplifyTop lie + + ; return (thing', const_binds) } + +\end{code} + %************************************************************************ %* *