2 % (c) The AQUA Project, Glasgow University, 1993-1998
4 \section[TcRules]{Typechecking transformation rules}
7 module TcRules ( tcIfaceRules, tcSourceRules ) where
9 #include "HsVersions.h"
11 import HsSyn ( RuleDecl(..), RuleBndr(..) )
12 import CoreSyn ( CoreRule(..) )
13 import RnHsSyn ( RenamedRuleDecl )
14 import HscTypes ( PackageRuleBase )
15 import TcHsSyn ( TypecheckedRuleDecl, mkHsLet )
17 import TcSimplify ( tcSimplifyToDicts, tcSimplifyInferCheck )
18 import TcType ( zonkTcTyVarToTyVar, newTyVarTy )
19 import TcIfaceSig ( tcCoreExpr, tcCoreLamBndrs, tcVar )
20 import TcMonoType ( kcHsSigType, tcHsSigType, tcTyVars, checkSigTyVars )
21 import TcExpr ( tcExpr )
22 import TcEnv ( tcExtendLocalValEnv, tcExtendTyVarEnv, isLocalThing )
23 import Rules ( extendRuleBase )
24 import Inst ( LIE, plusLIEs, instToId )
25 import Id ( idName, mkVanillaId )
26 import Module ( Module )
28 import Type ( tyVarsOfType, openTypeKind )
29 import List ( partition )
34 tcIfaceRules :: PackageRuleBase -> Module -> [RenamedRuleDecl]
35 -> TcM (PackageRuleBase, [TypecheckedRuleDecl])
36 tcIfaceRules pkg_rule_base mod decls
37 = mapTc tcIfaceRule decls `thenTc` \ new_rules ->
39 (local_rules, imported_rules) = partition is_local new_rules
40 new_rule_base = foldl add pkg_rule_base imported_rules
42 returnTc (new_rule_base, local_rules)
44 add rule_base (IfaceRuleOut id rule) = extendRuleBase rule_base (id, rule)
46 -- When relinking this module from its interface-file decls
47 -- we'll have IfaceRules that are in fact local to this module
48 is_local (IfaceRuleOut n _) = isLocalThing mod n
51 tcIfaceRule :: RenamedRuleDecl -> TcM TypecheckedRuleDecl
52 -- No zonking necessary!
53 tcIfaceRule (IfaceRule name vars fun args rhs src_loc)
54 = tcAddSrcLoc src_loc $
55 tcAddErrCtxt (ruleCtxt name) $
56 tcVar fun `thenTc` \ fun' ->
57 tcCoreLamBndrs vars $ \ vars' ->
58 mapTc tcCoreExpr args `thenTc` \ args' ->
59 tcCoreExpr rhs `thenTc` \ rhs' ->
60 returnTc (IfaceRuleOut fun' (Rule name vars' args' rhs'))
63 tcSourceRules :: [RenamedRuleDecl] -> TcM (LIE, [TypecheckedRuleDecl])
65 = mapAndUnzipTc tcSourceRule decls `thenTc` \ (lies, decls') ->
66 returnTc (plusLIEs lies, decls')
68 tcSourceRule (HsRule name sig_tvs vars lhs rhs src_loc)
69 = tcAddSrcLoc src_loc $
70 tcAddErrCtxt (ruleCtxt name) $
71 newTyVarTy openTypeKind `thenNF_Tc` \ rule_ty ->
73 -- Deal with the tyvars mentioned in signatures
74 tcTyVars sig_tvs (mapTc_ kcHsSigType sig_tys) `thenTc` \ sig_tyvars ->
75 tcExtendTyVarEnv sig_tyvars (
77 -- Ditto forall'd variables
78 mapNF_Tc new_id vars `thenNF_Tc` \ ids ->
79 tcExtendLocalValEnv [(idName id, id) | id <- ids] $
82 tcExpr lhs rule_ty `thenTc` \ (lhs', lhs_lie) ->
83 tcExpr rhs rule_ty `thenTc` \ (rhs', rhs_lie) ->
85 returnTc (sig_tyvars, ids, lhs', rhs', lhs_lie, rhs_lie)
86 ) `thenTc` \ (sig_tyvars, ids, lhs', rhs', lhs_lie, rhs_lie) ->
88 -- Check that LHS has no overloading at all
89 tcSimplifyToDicts lhs_lie `thenTc` \ (lhs_dicts, lhs_binds) ->
90 checkSigTyVars sig_tyvars emptyVarSet `thenTc_`
92 -- Gather the template variables and tyvars
94 tpl_ids = map instToId lhs_dicts ++ ids
96 -- IMPORTANT! We *quantify* over any dicts that appear in the LHS
98 -- a) The particular dictionary isn't important, because its value
99 -- depends only on the type
100 -- e.g gcd Int $fIntegralInt
101 -- Here we'd like to match against (gcd Int any_d) for any 'any_d'
103 -- b) We'd like to make available the dictionaries bound
104 -- on the LHS in the RHS, so quantifying over them is good
105 -- See the 'lhs_dicts' in tcSimplifyAndCheck for the RHS
108 -- RHS can be a bit more lenient. In particular,
109 -- we let constant dictionaries etc float outwards
110 tcSimplifyInferCheck (text "tcRule")
111 (varSetElems (tyVarsOfType rule_ty))
112 lhs_dicts rhs_lie `thenTc` \ (forall_tvs', lie', rhs_binds) ->
114 mapTc zonkTcTyVarToTyVar forall_tvs' `thenTc` \ tvs ->
115 returnTc (lie', HsRule name tvs
116 (map RuleBndr tpl_ids) -- yuk
117 (mkHsLet lhs_binds lhs')
118 (mkHsLet rhs_binds rhs')
121 sig_tys = [t | RuleBndrSig _ t <- vars]
123 new_id (RuleBndr var) = newTyVarTy openTypeKind `thenNF_Tc` \ ty ->
124 returnNF_Tc (mkVanillaId var ty)
125 new_id (RuleBndrSig var rn_ty) = tcHsSigType rn_ty `thenTc` \ ty ->
126 returnNF_Tc (mkVanillaId var ty)
128 ruleCtxt name = ptext SLIT("When checking the transformation rule") <+>
129 doubleQuotes (ptext name)