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% (c) The University of Glasgow 2006
% (c) The AQUA Project, Glasgow University, 1993-1998
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TcRules: Typechecking transformation rules
\begin{code}
<pre><a name="line-1"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>TcRules</span> <span class='hs-layout'>(</span> <span class='hs-varid'>tcRules</span> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>HsSyn</span>
<a name="line-4"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>TcRnMonad</span>
<a name="line-5"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>TcSimplify</span>
<a name="line-6"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>TcMType</span>
<a name="line-7"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>TcType</span>
<a name="line-8"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>TcHsType</span>
<a name="line-9"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>TcExpr</span>
<a name="line-10"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>TcEnv</span>
<a name="line-11"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Inst</span>
<a name="line-12"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Id</span>
<a name="line-13"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Name</span>
<a name="line-14"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>SrcLoc</span>
<a name="line-15"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Outputable</span>
<a name="line-16"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>FastString</span>
</pre>\end{code}
\begin{code}
<pre><a name="line-1"></a><a name="tcRules"></a><span class='hs-definition'>tcRules</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>LRuleDecl</span> <span class='hs-conid'>Name</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>TcM</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>LRuleDecl</span> <span class='hs-conid'>TcId</span><span class='hs-keyglyph'>]</span>
<a name="line-2"></a><span class='hs-definition'>tcRules</span> <span class='hs-varid'>decls</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mapM</span> <span class='hs-layout'>(</span><span class='hs-varid'>wrapLocM</span> <span class='hs-varid'>tcRule</span><span class='hs-layout'>)</span> <span class='hs-varid'>decls</span>
<a name="line-3"></a>
<a name="line-4"></a><a name="tcRule"></a><span class='hs-definition'>tcRule</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>RuleDecl</span> <span class='hs-conid'>Name</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>TcM</span> <span class='hs-layout'>(</span><span class='hs-conid'>RuleDecl</span> <span class='hs-conid'>TcId</span><span class='hs-layout'>)</span>
<a name="line-5"></a><span class='hs-definition'>tcRule</span> <span class='hs-layout'>(</span><span class='hs-conid'>HsRule</span> <span class='hs-varid'>name</span> <span class='hs-varid'>act</span> <span class='hs-varid'>vars</span> <span class='hs-varid'>lhs</span> <span class='hs-varid'>fv_lhs</span> <span class='hs-varid'>rhs</span> <span class='hs-varid'>fv_rhs</span><span class='hs-layout'>)</span>
<a name="line-6"></a> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>addErrCtxt</span> <span class='hs-layout'>(</span><span class='hs-varid'>ruleCtxt</span> <span class='hs-varid'>name</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-keyword'>do</span>
<a name="line-7"></a> <span class='hs-varid'>traceTc</span> <span class='hs-layout'>(</span><span class='hs-varid'>ptext</span> <span class='hs-layout'>(</span><span class='hs-varid'>sLit</span> <span class='hs-str'>"---- Rule ------"</span><span class='hs-layout'>)</span> <span class='hs-varop'><+></span> <span class='hs-varid'>ppr</span> <span class='hs-varid'>name</span><span class='hs-layout'>)</span>
<a name="line-8"></a> <span class='hs-varid'>rule_ty</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newFlexiTyVarTy</span> <span class='hs-varid'>openTypeKind</span>
<a name="line-9"></a>
<a name="line-10"></a> <span class='hs-comment'>-- Deal with the tyvars mentioned in signatures</span>
<a name="line-11"></a> <span class='hs-layout'>(</span><span class='hs-varid'>ids</span><span class='hs-layout'>,</span> <span class='hs-varid'>lhs'</span><span class='hs-layout'>,</span> <span class='hs-varid'>rhs'</span><span class='hs-layout'>,</span> <span class='hs-varid'>lhs_lie</span><span class='hs-layout'>,</span> <span class='hs-varid'>rhs_lie</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span>
<a name="line-12"></a> <span class='hs-varid'>tcRuleBndrs</span> <span class='hs-varid'>vars</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span> <span class='hs-varid'>ids</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-13"></a> <span class='hs-comment'>-- Now LHS and RHS</span>
<a name="line-14"></a> <span class='hs-layout'>(</span><span class='hs-varid'>lhs'</span><span class='hs-layout'>,</span> <span class='hs-varid'>lhs_lie</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>getLIE</span> <span class='hs-layout'>(</span><span class='hs-varid'>tcMonoExpr</span> <span class='hs-varid'>lhs</span> <span class='hs-varid'>rule_ty</span><span class='hs-layout'>)</span>
<a name="line-15"></a> <span class='hs-layout'>(</span><span class='hs-varid'>rhs'</span><span class='hs-layout'>,</span> <span class='hs-varid'>rhs_lie</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>getLIE</span> <span class='hs-layout'>(</span><span class='hs-varid'>tcMonoExpr</span> <span class='hs-varid'>rhs</span> <span class='hs-varid'>rule_ty</span><span class='hs-layout'>)</span>
<a name="line-16"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>ids</span><span class='hs-layout'>,</span> <span class='hs-varid'>lhs'</span><span class='hs-layout'>,</span> <span class='hs-varid'>rhs'</span><span class='hs-layout'>,</span> <span class='hs-varid'>lhs_lie</span><span class='hs-layout'>,</span> <span class='hs-varid'>rhs_lie</span><span class='hs-layout'>)</span>
<a name="line-17"></a>
<a name="line-18"></a> <span class='hs-comment'>-- Check that LHS has no overloading at all</span>
<a name="line-19"></a> <span class='hs-layout'>(</span><span class='hs-varid'>lhs_dicts</span><span class='hs-layout'>,</span> <span class='hs-varid'>lhs_binds</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>tcSimplifyRuleLhs</span> <span class='hs-varid'>lhs_lie</span>
<a name="line-20"></a>
<a name="line-21"></a> <span class='hs-comment'>-- Gather the template variables and tyvars</span>
<a name="line-22"></a> <span class='hs-keyword'>let</span>
<a name="line-23"></a> <span class='hs-varid'>tpl_ids</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>map</span> <span class='hs-varid'>instToId</span> <span class='hs-varid'>lhs_dicts</span> <span class='hs-varop'>++</span> <span class='hs-varid'>ids</span>
<a name="line-24"></a>
<a name="line-25"></a> <span class='hs-comment'>-- IMPORTANT! We *quantify* over any dicts that appear in the LHS</span>
<a name="line-26"></a> <span class='hs-comment'>-- Reason: </span>
<a name="line-27"></a> <span class='hs-comment'>-- a) The particular dictionary isn't important, because its value</span>
<a name="line-28"></a> <span class='hs-comment'>-- depends only on the type</span>
<a name="line-29"></a> <span class='hs-comment'>-- e.g gcd Int $fIntegralInt</span>
<a name="line-30"></a> <span class='hs-comment'>-- Here we'd like to match against (gcd Int any_d) for any 'any_d'</span>
<a name="line-31"></a> <span class='hs-comment'>--</span>
<a name="line-32"></a> <span class='hs-comment'>-- b) We'd like to make available the dictionaries bound </span>
<a name="line-33"></a> <span class='hs-comment'>-- on the LHS in the RHS, so quantifying over them is good</span>
<a name="line-34"></a> <span class='hs-comment'>-- See the 'lhs_dicts' in tcSimplifyAndCheck for the RHS</span>
<a name="line-35"></a>
<a name="line-36"></a> <span class='hs-comment'>-- We initially quantify over any tyvars free in *either* the rule</span>
<a name="line-37"></a> <span class='hs-comment'>-- *or* the bound variables. The latter is important. Consider</span>
<a name="line-38"></a> <span class='hs-comment'>-- ss (x,(y,z)) = (x,z)</span>
<a name="line-39"></a> <span class='hs-comment'>-- RULE: forall v. fst (ss v) = fst v</span>
<a name="line-40"></a> <span class='hs-comment'>-- The type of the rhs of the rule is just a, but v::(a,(b,c))</span>
<a name="line-41"></a> <span class='hs-comment'>--</span>
<a name="line-42"></a> <span class='hs-comment'>-- We also need to get the free tyvars of the LHS; but we do that</span>
<a name="line-43"></a> <span class='hs-comment'>-- during zonking (see TcHsSyn.zonkRule)</span>
<a name="line-44"></a> <span class='hs-comment'>--</span>
<a name="line-45"></a> <span class='hs-varid'>forall_tvs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>tyVarsOfTypes</span> <span class='hs-layout'>(</span><span class='hs-varid'>rule_ty</span> <span class='hs-conop'>:</span> <span class='hs-varid'>map</span> <span class='hs-varid'>idType</span> <span class='hs-varid'>tpl_ids</span><span class='hs-layout'>)</span>
<a name="line-46"></a>
<a name="line-47"></a> <span class='hs-comment'>-- RHS can be a bit more lenient. In particular,</span>
<a name="line-48"></a> <span class='hs-comment'>-- we let constant dictionaries etc float outwards</span>
<a name="line-49"></a> <span class='hs-comment'>--</span>
<a name="line-50"></a> <span class='hs-comment'>-- NB: tcSimplifyInferCheck zonks the forall_tvs, and </span>
<a name="line-51"></a> <span class='hs-comment'>-- knocks out any that are constrained by the environment</span>
<a name="line-52"></a> <span class='hs-varid'>loc</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>getInstLoc</span> <span class='hs-layout'>(</span><span class='hs-conid'>SigOrigin</span> <span class='hs-layout'>(</span><span class='hs-conid'>RuleSkol</span> <span class='hs-varid'>name</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-53"></a> <span class='hs-layout'>(</span><span class='hs-varid'>forall_tvs1</span><span class='hs-layout'>,</span> <span class='hs-varid'>rhs_binds</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>tcSimplifyInferCheck</span> <span class='hs-varid'>loc</span>
<a name="line-54"></a> <span class='hs-varid'>forall_tvs</span>
<a name="line-55"></a> <span class='hs-varid'>lhs_dicts</span> <span class='hs-varid'>rhs_lie</span>
<a name="line-56"></a>
<a name="line-57"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>HsRule</span> <span class='hs-varid'>name</span> <span class='hs-varid'>act</span>
<a name="line-58"></a> <span class='hs-layout'>(</span><span class='hs-varid'>map</span> <span class='hs-layout'>(</span><span class='hs-conid'>RuleBndr</span> <span class='hs-varop'>.</span> <span class='hs-varid'>noLoc</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>forall_tvs1</span> <span class='hs-varop'>++</span> <span class='hs-varid'>tpl_ids</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- yuk</span>
<a name="line-59"></a> <span class='hs-layout'>(</span><span class='hs-varid'>mkHsDictLet</span> <span class='hs-varid'>lhs_binds</span> <span class='hs-varid'>lhs'</span><span class='hs-layout'>)</span> <span class='hs-varid'>fv_lhs</span>
<a name="line-60"></a> <span class='hs-layout'>(</span><span class='hs-varid'>mkHsDictLet</span> <span class='hs-varid'>rhs_binds</span> <span class='hs-varid'>rhs'</span><span class='hs-layout'>)</span> <span class='hs-varid'>fv_rhs</span><span class='hs-layout'>)</span>
<a name="line-61"></a>
<a name="line-62"></a><a name="tcRuleBndrs"></a><span class='hs-definition'>tcRuleBndrs</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>RuleBndr</span> <span class='hs-conid'>Name</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>[</span><span class='hs-conid'>Id</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>TcM</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>TcM</span> <span class='hs-varid'>a</span>
<a name="line-63"></a><span class='hs-definition'>tcRuleBndrs</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>thing_inside</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>thing_inside</span> <span class='hs-conid'>[]</span>
<a name="line-64"></a><span class='hs-definition'>tcRuleBndrs</span> <span class='hs-layout'>(</span><span class='hs-conid'>RuleBndr</span> <span class='hs-varid'>var</span> <span class='hs-conop'>:</span> <span class='hs-varid'>vars</span><span class='hs-layout'>)</span> <span class='hs-varid'>thing_inside</span>
<a name="line-65"></a> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span> <span class='hs-layout'>{</span> <span class='hs-varid'>ty</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newFlexiTyVarTy</span> <span class='hs-varid'>openTypeKind</span>
<a name="line-66"></a> <span class='hs-layout'>;</span> <span class='hs-keyword'>let</span> <span class='hs-varid'>id</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mkLocalId</span> <span class='hs-layout'>(</span><span class='hs-varid'>unLoc</span> <span class='hs-varid'>var</span><span class='hs-layout'>)</span> <span class='hs-varid'>ty</span>
<a name="line-67"></a> <span class='hs-layout'>;</span> <span class='hs-varid'>tcExtendIdEnv</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>id</span><span class='hs-keyglyph'>]</span> <span class='hs-varop'>$</span>
<a name="line-68"></a> <span class='hs-varid'>tcRuleBndrs</span> <span class='hs-varid'>vars</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>ids</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>thing_inside</span> <span class='hs-layout'>(</span><span class='hs-varid'>id</span><span class='hs-conop'>:</span><span class='hs-varid'>ids</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-layout'>}</span>
<a name="line-69"></a><span class='hs-definition'>tcRuleBndrs</span> <span class='hs-layout'>(</span><span class='hs-conid'>RuleBndrSig</span> <span class='hs-varid'>var</span> <span class='hs-varid'>rn_ty</span> <span class='hs-conop'>:</span> <span class='hs-varid'>vars</span><span class='hs-layout'>)</span> <span class='hs-varid'>thing_inside</span>
<a name="line-70"></a><span class='hs-comment'>-- e.g x :: a->a</span>
<a name="line-71"></a><span class='hs-comment'>-- The tyvar 'a' is brought into scope first, just as if you'd written</span>
<a name="line-72"></a><span class='hs-comment'>-- a::*, x :: a->a</span>
<a name="line-73"></a> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span> <span class='hs-layout'>{</span> <span class='hs-keyword'>let</span> <span class='hs-varid'>ctxt</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FunSigCtxt</span> <span class='hs-layout'>(</span><span class='hs-varid'>unLoc</span> <span class='hs-varid'>var</span><span class='hs-layout'>)</span>
<a name="line-74"></a> <span class='hs-layout'>;</span> <span class='hs-layout'>(</span><span class='hs-varid'>tyvars</span><span class='hs-layout'>,</span> <span class='hs-varid'>ty</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>tcHsPatSigType</span> <span class='hs-varid'>ctxt</span> <span class='hs-varid'>rn_ty</span>
<a name="line-75"></a> <span class='hs-layout'>;</span> <span class='hs-keyword'>let</span> <span class='hs-varid'>skol_tvs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>tcSkolSigTyVars</span> <span class='hs-layout'>(</span><span class='hs-conid'>SigSkol</span> <span class='hs-varid'>ctxt</span><span class='hs-layout'>)</span> <span class='hs-varid'>tyvars</span>
<a name="line-76"></a> <span class='hs-varid'>id_ty</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>substTyWith</span> <span class='hs-varid'>tyvars</span> <span class='hs-layout'>(</span><span class='hs-varid'>mkTyVarTys</span> <span class='hs-varid'>skol_tvs</span><span class='hs-layout'>)</span> <span class='hs-varid'>ty</span>
<a name="line-77"></a> <span class='hs-varid'>id</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mkLocalId</span> <span class='hs-layout'>(</span><span class='hs-varid'>unLoc</span> <span class='hs-varid'>var</span><span class='hs-layout'>)</span> <span class='hs-varid'>id_ty</span>
<a name="line-78"></a> <span class='hs-layout'>;</span> <span class='hs-varid'>tcExtendTyVarEnv</span> <span class='hs-varid'>skol_tvs</span> <span class='hs-varop'>$</span>
<a name="line-79"></a> <span class='hs-varid'>tcExtendIdEnv</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>id</span><span class='hs-keyglyph'>]</span> <span class='hs-varop'>$</span>
<a name="line-80"></a> <span class='hs-varid'>tcRuleBndrs</span> <span class='hs-varid'>vars</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>ids</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>thing_inside</span> <span class='hs-layout'>(</span><span class='hs-varid'>id</span><span class='hs-conop'>:</span><span class='hs-varid'>ids</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-layout'>}</span>
<a name="line-81"></a>
<a name="line-82"></a><a name="ruleCtxt"></a><span class='hs-definition'>ruleCtxt</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FastString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>SDoc</span>
<a name="line-83"></a><span class='hs-definition'>ruleCtxt</span> <span class='hs-varid'>name</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ptext</span> <span class='hs-layout'>(</span><span class='hs-varid'>sLit</span> <span class='hs-str'>"When checking the transformation rule"</span><span class='hs-layout'>)</span> <span class='hs-varop'><+></span>
<a name="line-84"></a> <span class='hs-varid'>doubleQuotes</span> <span class='hs-layout'>(</span><span class='hs-varid'>ftext</span> <span class='hs-varid'>name</span><span class='hs-layout'>)</span>
</pre>\end{code}
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