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 TcMType ( newTyVarTy )
19 import TcType ( tyVarsOfTypes, openTypeKind )
20 import TcIfaceSig ( tcCoreExpr, tcCoreLamBndrs, tcVar, tcDelay )
21 import TcMonoType ( kcHsSigTypes, tcHsSigType, UserTypeCtxt(..), tcScopedTyVars )
22 import TcExpr ( tcExpr )
23 import TcEnv ( RecTcEnv, tcExtendLocalValEnv, isLocalThing )
24 import Rules ( extendRuleBase )
25 import Inst ( LIE, plusLIEs, instToId )
26 import Id ( idName, idType, mkLocalId )
27 import Module ( Module )
28 import List ( partition )
33 tcIfaceRules :: RecTcEnv -> PackageRuleBase -> Module -> [RenamedRuleDecl]
34 -> TcM (PackageRuleBase, [TypecheckedRuleDecl])
35 tcIfaceRules unf_env pkg_rule_base mod decls
36 = tcDelay unf_env doc [] (
37 -- We need the recursive env because the built-in rules show up as
38 -- IfaceOut rules, sot they get typechecked by tcIfaceRules
39 mapTc tcIfaceRule decls
40 ) `thenTc` \ new_rules ->
42 (local_rules, imported_rules) = partition is_local new_rules
43 new_rule_base = foldl add pkg_rule_base imported_rules
45 returnTc (new_rule_base, local_rules)
47 doc = text "tcIfaceRules"
48 add rule_base (IfaceRuleOut id rule) = extendRuleBase rule_base (id, rule)
50 -- When relinking this module from its interface-file decls
51 -- we'll have IfaceRules that are in fact local to this module
52 is_local (IfaceRuleOut n _) = isLocalThing mod n
55 tcIfaceRule :: RenamedRuleDecl -> TcM TypecheckedRuleDecl
56 -- No zonking necessary!
57 tcIfaceRule (IfaceRule name act vars fun args rhs src_loc)
58 = tcAddSrcLoc src_loc $
59 tcAddErrCtxt (ruleCtxt name) $
60 tcVar fun `thenTc` \ fun' ->
61 tcCoreLamBndrs vars $ \ vars' ->
62 mapTc tcCoreExpr args `thenTc` \ args' ->
63 tcCoreExpr rhs `thenTc` \ rhs' ->
64 returnTc (IfaceRuleOut fun' (Rule name act vars' args' rhs'))
66 tcIfaceRule (IfaceRuleOut fun rule) -- Built-in rules come this way
67 = tcVar fun `thenTc` \ fun' ->
68 returnTc (IfaceRuleOut fun' rule)
70 tcSourceRules :: [RenamedRuleDecl] -> TcM (LIE, [TypecheckedRuleDecl])
72 = mapAndUnzipTc tcSourceRule decls `thenTc` \ (lies, decls') ->
73 returnTc (plusLIEs lies, decls')
75 tcSourceRule (HsRule name act sig_tvs vars lhs rhs src_loc)
76 = tcAddSrcLoc src_loc $
77 tcAddErrCtxt (ruleCtxt name) $
78 newTyVarTy openTypeKind `thenNF_Tc` \ rule_ty ->
80 -- Deal with the tyvars mentioned in signatures
81 tcScopedTyVars sig_tvs (kcHsSigTypes sig_tys) (
83 -- Ditto forall'd variables
84 mapNF_Tc new_id vars `thenNF_Tc` \ ids ->
85 tcExtendLocalValEnv [(idName id, id) | id <- ids] $
88 tcExpr lhs rule_ty `thenTc` \ (lhs', lhs_lie) ->
89 tcExpr rhs rule_ty `thenTc` \ (rhs', rhs_lie) ->
91 returnTc (ids, lhs', rhs', lhs_lie, rhs_lie)
92 ) `thenTc` \ (ids, lhs', rhs', lhs_lie, rhs_lie) ->
94 -- Check that LHS has no overloading at all
95 tcSimplifyToDicts lhs_lie `thenTc` \ (lhs_dicts, lhs_binds) ->
97 -- Gather the template variables and tyvars
99 tpl_ids = map instToId lhs_dicts ++ ids
101 -- IMPORTANT! We *quantify* over any dicts that appear in the LHS
103 -- a) The particular dictionary isn't important, because its value
104 -- depends only on the type
105 -- e.g gcd Int $fIntegralInt
106 -- Here we'd like to match against (gcd Int any_d) for any 'any_d'
108 -- b) We'd like to make available the dictionaries bound
109 -- on the LHS in the RHS, so quantifying over them is good
110 -- See the 'lhs_dicts' in tcSimplifyAndCheck for the RHS
112 -- We initially quantify over any tyvars free in *either* the rule
113 -- *or* the bound variables. The latter is important. Consider
114 -- ss (x,(y,z)) = (x,z)
115 -- RULE: forall v. fst (ss v) = fst v
116 -- The type of the rhs of the rule is just a, but v::(a,(b,c))
118 -- It's still conceivable that there may be type variables mentioned
119 -- in the LHS, but not in the type of the lhs, nor in the binders.
120 -- They'll get zapped to (), but that's over-constraining really.
121 -- Let's see if we get a problem.
122 forall_tvs = tyVarsOfTypes (rule_ty : map idType tpl_ids)
125 -- RHS can be a bit more lenient. In particular,
126 -- we let constant dictionaries etc float outwards
129 tcSimplifyInferCheck (text "tcRule")
131 lhs_dicts rhs_lie `thenTc` \ (forall_tvs1, lie', rhs_binds) ->
133 returnTc (lie', HsRule name act forall_tvs1
134 (map RuleBndr tpl_ids) -- yuk
135 (mkHsLet lhs_binds lhs')
136 (mkHsLet rhs_binds rhs')
139 sig_tys = [t | RuleBndrSig _ t <- vars]
141 new_id (RuleBndr var) = newTyVarTy openTypeKind `thenNF_Tc` \ ty ->
142 returnNF_Tc (mkLocalId var ty)
143 new_id (RuleBndrSig var rn_ty) = tcHsSigType (RuleSigCtxt var) rn_ty `thenTc` \ ty ->
144 returnNF_Tc (mkLocalId var ty)
146 ruleCtxt name = ptext SLIT("When checking the transformation rule") <+>
147 doubleQuotes (ptext name)