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source: src/ResolvExpr/Unify.cc @ b93c544

Last change on this file since b93c544 was bbf2cb1, checked in by JiadaL <j82liang@…>, 4 months ago
Add the Working support to succ() and pred() pseudo function to Enum
Property mode set to `100644`
File size: 23.2 KB

Rev	Line
[a32b204]	1	//
	2	// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
	3	//
	4	// The contents of this file are covered under the licence agreement in the
	5	// file "LICENCE" distributed with Cforall.
	6	//
[41a2620]	7	// Unify.cc --
[a32b204]	8	//
	9	// Author : Richard C. Bilson
	10	// Created On : Sun May 17 12:27:10 2015
[07de76b]	11	// Last Modified By : Peter A. Buhr
	12	// Last Modified On : Fri Dec 13 23:43:05 2019
	13	// Update Count : 46
[a32b204]	14	//
[51b7345]	15
[f474e91]	16	#include "Unify.h"
	17
[d76c588]	18	#include <cassert> // for assertf, assert
	19	#include <iterator> // for back_insert_iterator, back_inserter
	20	#include <map> // for _Rb_tree_const_iterator, _Rb_tree_i...
	21	#include <memory> // for unique_ptr
	22	#include <set> // for set
	23	#include <string> // for string, operator==, operator!=, bas...
	24	#include <utility> // for pair, move
[54e41b3]	25	#include <vector>
[51b7345]	26
[2890212]	27	#include "AST/Copy.hpp"
[f474e91]	28	#include "AST/Decl.hpp"
[54e41b3]	29	#include "AST/Node.hpp"
[f474e91]	30	#include "AST/Pass.hpp"
[2890212]	31	#include "AST/Print.hpp"
[54e41b3]	32	#include "AST/Type.hpp"
[d76c588]	33	#include "AST/TypeEnvironment.hpp"
[f02f546]	34	#include "Common/Eval.h" // for eval
[5bf3976]	35	#include "CommonType.hpp" // for commonType
[d76c588]	36	#include "FindOpenVars.h" // for findOpenVars
[5bf3976]	37	#include "SpecCost.hpp" // for SpecCost
[d76c588]	38	#include "Tuples/Tuples.h" // for isTtype
[5bf3976]	39	#include "typeops.h" // for flatten, occurs
[ea6332d]	40
[f474e91]	41	namespace ast {
	42	class SymbolTable;
	43	}
	44
[1cbca6e]	45	// #define DEBUG
[51b7345]	46
	47	namespace ResolvExpr {
	48
[7870799]	49	bool typesCompatible(
[251ce80]	50	const ast::Type * first, const ast::Type * second,
[d76c588]	51	const ast::TypeEnvironment & env ) {
[f474e91]	52	ast::TypeEnvironment newEnv;
	53	ast::OpenVarSet open, closed;
	54	ast::AssertionSet need, have;
	55
	56	ast::ptr<ast::Type> newFirst{ first }, newSecond{ second };
	57	env.apply( newFirst );
	58	env.apply( newSecond );
	59
[46da46b]	60	// findOpenVars( newFirst, open, closed, need, have, FirstClosed );
	61	findOpenVars( newSecond, open, closed, need, have, newEnv, FirstOpen );
[f474e91]	62
[251ce80]	63	return unifyExact(newFirst, newSecond, newEnv, need, have, open, noWiden() );
[d76c588]	64	}
	65
[7870799]	66	bool typesCompatibleIgnoreQualifiers(
[251ce80]	67	const ast::Type * first, const ast::Type * second,
[d76c588]	68	const ast::TypeEnvironment & env ) {
[f474e91]	69	ast::TypeEnvironment newEnv;
	70	ast::OpenVarSet open;
	71	ast::AssertionSet need, have;
[7870799]	72
[2890212]	73	ast::Type * newFirst = shallowCopy( first );
	74	ast::Type * newSecond = shallowCopy( second );
[b729c01]	75
[2890212]	76	newFirst ->qualifiers = {};
	77	newSecond->qualifiers = {};
[f49b3fc]	78	ast::ptr< ast::Type > t1_(newFirst );
	79	ast::ptr< ast::Type > t2_(newSecond);
[f474e91]	80
[c7f834e]	81	ast::ptr< ast::Type > subFirst = env.apply(newFirst).node;
	82	ast::ptr< ast::Type > subSecond = env.apply(newSecond).node;
	83
[7870799]	84	return unifyExact(
[c7f834e]	85	subFirst,
	86	subSecond,
[251ce80]	87	newEnv, need, have, open, noWiden() );
[d76c588]	88	}
	89
[ef1da0e2]	90	namespace {
	91	/// Replaces ttype variables with their bound types.
	92	/// If this isn't done when satifying ttype assertions, then argument lists can have
	93	/// different size and structure when they should be compatible.
[0bd3faf]	94	struct TtypeExpander : public ast::WithShortCircuiting, public ast::PureVisitor {
[ef1da0e2]	95	ast::TypeEnvironment & tenv;
	96
[0bd3faf]	97	TtypeExpander( ast::TypeEnvironment & env ) : tenv( env ) {}
[ef1da0e2]	98
	99	const ast::Type * postvisit( const ast::TypeInstType * typeInst ) {
	100	if ( const ast::EqvClass * clz = tenv.lookup( *typeInst ) ) {
	101	// expand ttype parameter into its actual type
	102	if ( clz->data.kind == ast::TypeDecl::Ttype && clz->bound ) {
	103	return clz->bound;
	104	}
	105	}
	106	return typeInst;
	107	}
	108	};
	109	}
[0bd46fd]	110
[ef1da0e2]	111	std::vector< ast::ptr< ast::Type > > flattenList(
	112	const std::vector< ast::ptr< ast::Type > > & src, ast::TypeEnvironment & env
	113	) {
	114	std::vector< ast::ptr< ast::Type > > dst;
	115	dst.reserve( src.size() );
	116	for ( const auto & d : src ) {
[0bd3faf]	117	ast::Pass<TtypeExpander> expander{ env };
[ef1da0e2]	118	// TtypeExpander pass is impure (may mutate nodes in place)
	119	// need to make nodes shared to prevent accidental mutation
	120	ast::ptr<ast::Type> dc = d->accept(expander);
	121	auto types = flatten( dc );
	122	for ( ast::ptr< ast::Type > & t : types ) {
	123	// outermost const, volatile, _Atomic qualifiers in parameters should not play
	124	// a role in the unification of function types, since they do not determine
	125	// whether a function is callable.
	126	// NOTE: must consider at least mutex qualifier, since functions can be
	127	// overloaded on outermost mutex and a mutex function has different
	128	// requirements than a non-mutex function
	129	remove_qualifiers( t, ast::CV::Const \| ast::CV::Volatile \| ast::CV::Atomic );
	130	dst.emplace_back( t );
	131	}
	132	}
	133	return dst;
	134	}
	135
[f02f546]	136	// Unification of Expressions
	137	//
	138	// Boolean outcome (obvious): Are they basically spelled the same?
	139	// Side effect of binding variables (subtle): if `sizeof(int)` ===_expr `sizeof(T)` then `int` ===_ty `T`
	140	//
	141	// Context: if `float[VAREXPR1]` ===_ty `float[VAREXPR2]` then `VAREXPR1` ===_expr `VAREXPR2`
	142	// where the VAREXPR are meant as notational metavariables representing the fact that unification always
	143	// sees distinct ast::VariableExpr objects at these positions
	144
	145	static bool unify( const ast::Expr * e1, const ast::Expr * e2, ast::TypeEnvironment & env,
	146	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open,
	147	WidenMode widen );
	148
	149	class UnifyExpr final : public ast::WithShortCircuiting {
	150	const ast::Expr * e2;
	151	ast::TypeEnvironment & tenv;
	152	ast::AssertionSet & need;
	153	ast::AssertionSet & have;
	154	const ast::OpenVarSet & open;
	155	WidenMode widen;
	156	public:
	157	bool result;
	158
	159	private:
	160
	161	void tryMatchOnStaticValue( const ast::Expr * e1 ) {
	162	Evaluation r1 = eval(e1);
	163	Evaluation r2 = eval(e2);
	164
	165	if ( ! r1.hasKnownValue ) return;
	166	if ( ! r2.hasKnownValue ) return;
	167
	168	if (r1.knownValue != r2.knownValue) return;
	169
	170	visit_children = false;
	171	result = true;
	172	}
	173
	174	public:
	175
	176	void previsit( const ast::Node * ) { assert(false); }
	177
	178	void previsit( const ast::Expr * e1 ) {
	179	tryMatchOnStaticValue( e1 );
	180	visit_children = false;
	181	}
	182
	183	void previsit( const ast::CastExpr * e1 ) {
	184	tryMatchOnStaticValue( e1 );
	185
	186	if (result) {
	187	assert (visit_children == false);
	188	} else {
	189	assert (visit_children == true);
	190	visit_children = false;
	191
	192	auto e2c = dynamic_cast< const ast::CastExpr * >( e2 );
	193	if ( ! e2c ) return;
	194
	195	// inspect casts' target types
	196	if ( ! unifyExact(
	197	e1->result, e2c->result, tenv, need, have, open, widen ) ) return;
	198
	199	// inspect casts' inner expressions
	200	result = unify( e1->arg, e2c->arg, tenv, need, have, open, widen );
	201	}
	202	}
	203
	204	void previsit( const ast::VariableExpr * e1 ) {
	205	tryMatchOnStaticValue( e1 );
	206
	207	if (result) {
	208	assert (visit_children == false);
	209	} else {
	210	assert (visit_children == true);
	211	visit_children = false;
	212
	213	auto e2v = dynamic_cast< const ast::VariableExpr * >( e2 );
	214	if ( ! e2v ) return;
	215
	216	assert(e1->var);
	217	assert(e2v->var);
	218
	219	// conservative: variable exprs match if their declarations are represented by the same C++ AST object
	220	result = (e1->var == e2v->var);
	221	}
	222	}
	223
	224	void previsit( const ast::SizeofExpr * e1 ) {
	225	tryMatchOnStaticValue( e1 );
	226
	227	if (result) {
	228	assert (visit_children == false);
	229	} else {
	230	assert (visit_children == true);
	231	visit_children = false;
	232
	233	auto e2so = dynamic_cast< const ast::SizeofExpr * >( e2 );
	234	if ( ! e2so ) return;
	235
	236	assert((e1->type != nullptr) ^ (e1->expr != nullptr));
	237	assert((e2so->type != nullptr) ^ (e2so->expr != nullptr));
	238	if ( ! (e1->type && e2so->type) ) return;
	239
	240	// expression unification calls type unification (mutual recursion)
	241	result = unifyExact( e1->type, e2so->type, tenv, need, have, open, widen );
	242	}
	243	}
	244
	245	UnifyExpr( const ast::Expr * e2, ast::TypeEnvironment & env, ast::AssertionSet & need,
	246	ast::AssertionSet & have, const ast::OpenVarSet & open, WidenMode widen )
	247	: e2( e2 ), tenv(env), need(need), have(have), open(open), widen(widen), result(false) {}
	248	};
	249
	250	static bool unify( const ast::Expr * e1, const ast::Expr * e2, ast::TypeEnvironment & env,
	251	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open,
	252	WidenMode widen ) {
	253	assert( e1 && e2 );
	254	return ast::Pass<UnifyExpr>::read( e1, e2, env, need, have, open, widen );
	255	}
	256
[0bd3faf]	257	class Unify final : public ast::WithShortCircuiting {
[f474e91]	258	const ast::Type * type2;
	259	ast::TypeEnvironment & tenv;
	260	ast::AssertionSet & need;
	261	ast::AssertionSet & have;
	262	const ast::OpenVarSet & open;
	263	WidenMode widen;
	264	public:
[c15085d]	265	static size_t traceId;
[f474e91]	266	bool result;
	267
[0bd3faf]	268	Unify(
[7870799]	269	const ast::Type * type2, ast::TypeEnvironment & env, ast::AssertionSet & need,
[251ce80]	270	ast::AssertionSet & have, const ast::OpenVarSet & open, WidenMode widen )
[7870799]	271	: type2(type2), tenv(env), need(need), have(have), open(open), widen(widen),
[251ce80]	272	result(false) {}
[f474e91]	273
	274	void previsit( const ast::Node * ) { visit_children = false; }
[7870799]	275
[ee574a2]	276	void postvisit( const ast::VoidType * ) {
[f474e91]	277	result = dynamic_cast< const ast::VoidType * >( type2 );
	278	}
	279
[ee574a2]	280	void postvisit( const ast::BasicType * basic ) {
[f474e91]	281	if ( auto basic2 = dynamic_cast< const ast::BasicType * >( type2 ) ) {
	282	result = basic->kind == basic2->kind;
	283	}
	284	}
	285
[ee574a2]	286	void postvisit( const ast::PointerType * pointer ) {
[f474e91]	287	if ( auto pointer2 = dynamic_cast< const ast::PointerType * >( type2 ) ) {
[7870799]	288	result = unifyExact(
	289	pointer->base, pointer2->base, tenv, need, have, open,
[251ce80]	290	noWiden());
[f474e91]	291	}
	292	}
	293
[ee574a2]	294	void postvisit( const ast::ArrayType * array ) {
[f474e91]	295	auto array2 = dynamic_cast< const ast::ArrayType * >( type2 );
	296	if ( ! array2 ) return;
	297
	298	if ( array->isVarLen != array2->isVarLen ) return;
[f02f546]	299	if ( (array->dimension != nullptr) != (array2->dimension != nullptr) ) return;
[f474e91]	300
[f02f546]	301	if ( array->dimension ) {
	302	assert( array2->dimension );
	303	// type unification calls expression unification (mutual recursion)
	304	if ( ! unify(array->dimension, array2->dimension,
	305	tenv, need, have, open, widen) ) return;
[f474e91]	306	}
	307
[7870799]	308	result = unifyExact(
[251ce80]	309	array->base, array2->base, tenv, need, have, open, noWiden());
[f474e91]	310	}
	311
[ee574a2]	312	void postvisit( const ast::ReferenceType * ref ) {
[f474e91]	313	if ( auto ref2 = dynamic_cast< const ast::ReferenceType * >( type2 ) ) {
[7870799]	314	result = unifyExact(
[251ce80]	315	ref->base, ref2->base, tenv, need, have, open, noWiden());
[f474e91]	316	}
	317	}
	318
	319	private:
	320
	321	template< typename Iter >
[954c954]	322	static bool unifyTypeList(
[7870799]	323	Iter crnt1, Iter end1, Iter crnt2, Iter end2, ast::TypeEnvironment & env,
[251ce80]	324	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open
[f474e91]	325	) {
	326	while ( crnt1 != end1 && crnt2 != end2 ) {
[954c954]	327	const ast::Type * t1 = *crnt1;
	328	const ast::Type * t2 = *crnt2;
[f474e91]	329	bool isTuple1 = Tuples::isTtype( t1 );
	330	bool isTuple2 = Tuples::isTtype( t2 );
	331
	332	// assumes here that ttype must be last parameter
	333	if ( isTuple1 && ! isTuple2 ) {
	334	// combine remainder of list2, then unify
[7870799]	335	return unifyExact(
[954c954]	336	t1, tupleFromTypes( crnt2, end2 ), env, need, have, open,
[251ce80]	337	noWiden() );
[f474e91]	338	} else if ( ! isTuple1 && isTuple2 ) {
	339	// combine remainder of list1, then unify
[7870799]	340	return unifyExact(
[954c954]	341	tupleFromTypes( crnt1, end1 ), t2, env, need, have, open,
[251ce80]	342	noWiden() );
[f474e91]	343	}
	344
[7870799]	345	if ( ! unifyExact(
[251ce80]	346	t1, t2, env, need, have, open, noWiden() )
[f474e91]	347	) return false;
	348
	349	++crnt1; ++crnt2;
	350	}
	351
[7870799]	352	// May get to the end of one argument list before the other. This is only okay if the
[f474e91]	353	// other is a ttype
	354	if ( crnt1 != end1 ) {
	355	// try unifying empty tuple with ttype
[954c954]	356	const ast::Type * t1 = *crnt1;
[f474e91]	357	if ( ! Tuples::isTtype( t1 ) ) return false;
[7870799]	358	return unifyExact(
[954c954]	359	t1, tupleFromTypes( crnt2, end2 ), env, need, have, open,
[251ce80]	360	noWiden() );
[f474e91]	361	} else if ( crnt2 != end2 ) {
	362	// try unifying empty tuple with ttype
[954c954]	363	const ast::Type * t2 = *crnt2;
[f474e91]	364	if ( ! Tuples::isTtype( t2 ) ) return false;
[7870799]	365	return unifyExact(
[954c954]	366	tupleFromTypes( crnt1, end1 ), t2, env, need, have, open,
[251ce80]	367	noWiden() );
[f474e91]	368	}
	369
	370	return true;
	371	}
	372
[954c954]	373	static bool unifyTypeList(
	374	const std::vector< ast::ptr< ast::Type > > & list1,
	375	const std::vector< ast::ptr< ast::Type > > & list2,
[7870799]	376	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
[251ce80]	377	const ast::OpenVarSet & open
[f474e91]	378	) {
[954c954]	379	return unifyTypeList(
[251ce80]	380	list1.begin(), list1.end(), list2.begin(), list2.end(), env, need, have, open);
[f474e91]	381	}
	382
[3e5dd913]	383	static void markAssertionSet( ast::AssertionSet & assns, const ast::VariableExpr * assn ) {
[f474e91]	384	auto i = assns.find( assn );
	385	if ( i != assns.end() ) {
	386	i->second.isUsed = true;
	387	}
	388	}
	389
	390	/// mark all assertions in `type` used in both `assn1` and `assn2`
[7870799]	391	static void markAssertions(
	392	ast::AssertionSet & assn1, ast::AssertionSet & assn2,
[361bf01]	393	const ast::FunctionType * type
[f474e91]	394	) {
[3e5dd913]	395	for ( auto & assert : type->assertions ) {
	396	markAssertionSet( assn1, assert );
	397	markAssertionSet( assn2, assert );
[f474e91]	398	}
	399	}
	400
	401	public:
[ee574a2]	402	void postvisit( const ast::FunctionType * func ) {
[f474e91]	403	auto func2 = dynamic_cast< const ast::FunctionType * >( type2 );
	404	if ( ! func2 ) return;
	405
	406	if ( func->isVarArgs != func2->isVarArgs ) return;
[7870799]	407
	408	// Flatten the parameter lists for both functions so that tuple structure does not
[f474e91]	409	// affect unification. Does not actually mutate function parameters.
	410	auto params = flattenList( func->params, tenv );
	411	auto params2 = flattenList( func2->params, tenv );
	412
[7870799]	413	// sizes don't have to match if ttypes are involved; need to be more precise w.r.t.
[f474e91]	414	// where the ttype is to prevent errors
[7870799]	415	if (
[f474e91]	416	( params.size() != params2.size() \|\| func->returns.size() != func2->returns.size() )
	417	&& ! func->isTtype()
	418	&& ! func2->isTtype()
	419	) return;
	420
[251ce80]	421	if ( ! unifyTypeList( params, params2, tenv, need, have, open ) ) return;
[954c954]	422	if ( ! unifyTypeList(
[251ce80]	423	func->returns, func2->returns, tenv, need, have, open ) ) return;
[7870799]	424
[f474e91]	425	markAssertions( have, need, func );
	426	markAssertions( have, need, func2 );
	427
	428	result = true;
	429	}
[7870799]	430
[f474e91]	431	private:
[90ce35aa]	432	// Returns: other, cast as XInstType
	433	// Assigns this->result: whether types are compatible (up to generic parameters)
	434	template< typename XInstType >
	435	const XInstType * handleRefType( const XInstType * inst, const ast::Type * other ) {
[f474e91]	436	// check that the other type is compatible and named the same
[90ce35aa]	437	auto otherInst = dynamic_cast< const XInstType * >( other );
[24d6572]	438	if (otherInst && inst->name == otherInst->name)
	439	this->result = otherInst;
[f474e91]	440	return otherInst;
	441	}
	442
	443	/// Creates a tuple type based on a list of TypeExpr
	444	template< typename Iter >
[7870799]	445	static const ast::Type * tupleFromExprs(
[f474e91]	446	const ast::TypeExpr * param, Iter & crnt, Iter end, ast::CV::Qualifiers qs
	447	) {
	448	std::vector< ast::ptr< ast::Type > > types;
	449	do {
	450	types.emplace_back( param->type );
	451
	452	++crnt;
	453	if ( crnt == end ) break;
	454	param = strict_dynamic_cast< const ast::TypeExpr * >( crnt->get() );
	455	} while(true);
	456
	457	return new ast::TupleType{ std::move(types), qs };
	458	}
	459
[90ce35aa]	460	template< typename XInstType >
	461	void handleGenericRefType( const XInstType * inst, const ast::Type * other ) {
[f474e91]	462	// check that other type is compatible and named the same
[90ce35aa]	463	const XInstType * otherInst = handleRefType( inst, other );
	464	if ( ! this->result ) return;
[7870799]	465
[f474e91]	466	// check that parameters of types unify, if any
	467	const std::vector< ast::ptr< ast::Expr > > & params = inst->params;
[90ce35aa]	468	const std::vector< ast::ptr< ast::Expr > > & params2 = otherInst->params;
[f474e91]	469
	470	auto it = params.begin();
	471	auto jt = params2.begin();
	472	for ( ; it != params.end() && jt != params2.end(); ++it, ++jt ) {
	473	auto param = strict_dynamic_cast< const ast::TypeExpr * >( it->get() );
	474	auto param2 = strict_dynamic_cast< const ast::TypeExpr * >( jt->get() );
	475
	476	ast::ptr< ast::Type > pty = param->type;
	477	ast::ptr< ast::Type > pty2 = param2->type;
	478
	479	bool isTuple = Tuples::isTtype( pty );
	480	bool isTuple2 = Tuples::isTtype( pty2 );
	481
	482	if ( isTuple && isTuple2 ) {
	483	++it; ++jt; // skip ttype parameters before break
[0bd46fd]	484	} else if ( isTuple ) {
[f474e91]	485	// bundle remaining params into tuple
	486	pty2 = tupleFromExprs( param2, jt, params2.end(), pty->qualifiers );
	487	++it; // skip ttype parameter for break
	488	} else if ( isTuple2 ) {
	489	// bundle remaining params into tuple
	490	pty = tupleFromExprs( param, it, params.end(), pty2->qualifiers );
	491	++jt; // skip ttype parameter for break
	492	}
	493
[7870799]	494	if ( ! unifyExact(
[251ce80]	495	pty, pty2, tenv, need, have, open, noWiden() ) ) {
[f474e91]	496	result = false;
	497	return;
	498	}
	499
	500	// ttype parameter should be last
	501	if ( isTuple \|\| isTuple2 ) break;
	502	}
	503	result = it == params.end() && jt == params2.end();
	504	}
	505
	506	public:
[ee574a2]	507	void postvisit( const ast::StructInstType * aggrType ) {
[f474e91]	508	handleGenericRefType( aggrType, type2 );
	509	}
	510
[ee574a2]	511	void postvisit( const ast::UnionInstType * aggrType ) {
[f474e91]	512	handleGenericRefType( aggrType, type2 );
	513	}
	514
[ee574a2]	515	void postvisit( const ast::EnumInstType * aggrType ) {
[f474e91]	516	handleRefType( aggrType, type2 );
	517	}
	518
[f1149ac]	519	void postvisit( const ast::EnumPosType * ) {
[bbf2cb1]	520	// Lazy approach for now
	521	auto otherPos = dynamic_cast< const ast::EnumPosType *>(type2);
	522	if (otherPos) this->result = otherPos;
[0522ebe]	523	}
	524
[ee574a2]	525	void postvisit( const ast::TraitInstType * aggrType ) {
[f474e91]	526	handleRefType( aggrType, type2 );
	527	}
	528
[ee574a2]	529	void postvisit( const ast::TypeInstType * typeInst ) {
[46da46b]	530	// assert( open.find( *typeInst ) == open.end() );
[24d6572]	531	auto otherInst = dynamic_cast< const ast::TypeInstType * >( type2 );
[2908f08]	532	if ( otherInst && typeInst->name == otherInst->name ) {
[24d6572]	533	this->result = otherInst;
[2908f08]	534	}
[f474e91]	535	}
	536
	537	private:
	538	/// Creates a tuple type based on a list of Type
[0bd46fd]	539
[7870799]	540	static bool unifyList(
	541	const std::vector< ast::ptr< ast::Type > > & list1,
	542	const std::vector< ast::ptr< ast::Type > > & list2, ast::TypeEnvironment & env,
[251ce80]	543	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open
[f474e91]	544	) {
	545	auto crnt1 = list1.begin();
	546	auto crnt2 = list2.begin();
	547	while ( crnt1 != list1.end() && crnt2 != list2.end() ) {
	548	const ast::Type * t1 = *crnt1;
	549	const ast::Type * t2 = *crnt2;
	550	bool isTuple1 = Tuples::isTtype( t1 );
	551	bool isTuple2 = Tuples::isTtype( t2 );
	552
	553	// assumes ttype must be last parameter
	554	if ( isTuple1 && ! isTuple2 ) {
	555	// combine entirety of list2, then unify
[7870799]	556	return unifyExact(
	557	t1, tupleFromTypes( list2 ), env, need, have, open,
[251ce80]	558	noWiden() );
[f474e91]	559	} else if ( ! isTuple1 && isTuple2 ) {
	560	// combine entirety of list1, then unify
	561	return unifyExact(
[7870799]	562	tupleFromTypes( list1 ), t2, env, need, have, open,
[251ce80]	563	noWiden() );
[f474e91]	564	}
	565
[7870799]	566	if ( ! unifyExact(
[251ce80]	567	t1, t2, env, need, have, open, noWiden() )
[f474e91]	568	) return false;
	569
	570	++crnt1; ++crnt2;
	571	}
	572
	573	if ( crnt1 != list1.end() ) {
	574	// try unifying empty tuple type with ttype
	575	const ast::Type * t1 = *crnt1;
	576	if ( ! Tuples::isTtype( t1 ) ) return false;
[7870799]	577	// xxx - this doesn't generate an empty tuple, contrary to comment; both ported
[f474e91]	578	// from Rob's code
[7870799]	579	return unifyExact(
	580	t1, tupleFromTypes( list2 ), env, need, have, open,
[251ce80]	581	noWiden() );
[f474e91]	582	} else if ( crnt2 != list2.end() ) {
	583	// try unifying empty tuple with ttype
	584	const ast::Type * t2 = *crnt2;
	585	if ( ! Tuples::isTtype( t2 ) ) return false;
[7870799]	586	// xxx - this doesn't generate an empty tuple, contrary to comment; both ported
[f474e91]	587	// from Rob's code
	588	return unifyExact(
[7870799]	589	tupleFromTypes( list1 ), t2, env, need, have, open,
[251ce80]	590	noWiden() );
[f474e91]	591	}
	592
	593	return true;
	594	}
	595
	596	public:
[ee574a2]	597	void postvisit( const ast::TupleType * tuple ) {
[f474e91]	598	auto tuple2 = dynamic_cast< const ast::TupleType * >( type2 );
	599	if ( ! tuple2 ) return;
	600
[0bd3faf]	601	ast::Pass<TtypeExpander> expander{ tenv };
[ef9988b]	602
[d3aa64f1]	603	const ast::Type * flat = tuple->accept( expander );
	604	const ast::Type * flat2 = tuple2->accept( expander );
[f474e91]	605
	606	auto types = flatten( flat );
	607	auto types2 = flatten( flat2 );
	608
[251ce80]	609	result = unifyList( types, types2, tenv, need, have, open );
[f474e91]	610	}
	611
[ee574a2]	612	void postvisit( const ast::VarArgsType * ) {
[f474e91]	613	result = dynamic_cast< const ast::VarArgsType * >( type2 );
	614	}
	615
[ee574a2]	616	void postvisit( const ast::ZeroType * ) {
[f474e91]	617	result = dynamic_cast< const ast::ZeroType * >( type2 );
	618	}
	619
[ee574a2]	620	void postvisit( const ast::OneType * ) {
[f474e91]	621	result = dynamic_cast< const ast::OneType * >( type2 );
[7870799]	622	}
[f474e91]	623	};
	624
[0bd3faf]	625	// size_t Unify::traceId = Stats::Heap::new_stacktrace_id("Unify");
	626
[7870799]	627	bool unify(
	628	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
	629	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
[251ce80]	630	ast::OpenVarSet & open
[2773ab8]	631	) {
	632	ast::ptr<ast::Type> common;
[251ce80]	633	return unify( type1, type2, env, need, have, open, common );
[2773ab8]	634	}
	635
[7870799]	636	bool unify(
	637	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
	638	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
[251ce80]	639	ast::OpenVarSet & open, ast::ptr<ast::Type> & common
[ee574a2]	640	) {
	641	ast::OpenVarSet closed;
[46da46b]	642	// findOpenVars( type1, open, closed, need, have, FirstClosed );
	643	findOpenVars( type2, open, closed, need, have, env, FirstOpen );
[7870799]	644	return unifyInexact(
[251ce80]	645	type1, type2, env, need, have, open, WidenMode{ true, true }, common );
[ee574a2]	646	}
	647
[7870799]	648	bool unifyExact(
	649	const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env,
	650	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open,
[251ce80]	651	WidenMode widen
[f474e91]	652	) {
	653	if ( type1->qualifiers != type2->qualifiers ) return false;
	654
	655	auto var1 = dynamic_cast< const ast::TypeInstType * >( type1 );
	656	auto var2 = dynamic_cast< const ast::TypeInstType * >( type2 );
[46da46b]	657	bool isopen1 = var1 && env.lookup(*var1);
	658	bool isopen2 = var2 && env.lookup(*var2);
[f474e91]	659
[46da46b]	660	if ( isopen1 && isopen2 ) {
	661	if ( var1->base->kind != var2->base->kind ) return false;
	662	return env.bindVarToVar(
	663	var1, var2, ast::TypeData{ var1->base->kind, var1->base->sized\|\|var2->base->sized }, need, have,
[24d6572]	664	open, widen );
[46da46b]	665	} else if ( isopen1 ) {
[24d6572]	666	return env.bindVar( var1, type2, ast::TypeData{var1->base}, need, have, open, widen );
[46da46b]	667	} else if ( isopen2 ) {
[24d6572]	668	return env.bindVar( var2, type1, ast::TypeData{var2->base}, need, have, open, widen );
[8f31be6]	669	} else {
[0bd3faf]	670	return ast::Pass<Unify>::read(
[251ce80]	671	type1, type2, env, need, have, open, widen );
[f474e91]	672	}
	673	}
	674
[7870799]	675	bool unifyInexact(
	676	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
	677	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
[251ce80]	678	const ast::OpenVarSet & open, WidenMode widen,
[7870799]	679	ast::ptr<ast::Type> & common
[f474e91]	680	) {
	681	ast::CV::Qualifiers q1 = type1->qualifiers, q2 = type2->qualifiers;
[7870799]	682
	683	// force t1 and t2 to be cloned if their qualifiers must be stripped, so that type1 and
[f474e91]	684	// type2 are left unchanged; calling convention forces type{1,2}->strong_ref >= 1
[2890212]	685	ast::Type * t1 = shallowCopy(type1.get());
	686	ast::Type * t2 = shallowCopy(type2.get());
	687	t1->qualifiers = {};
	688	t2->qualifiers = {};
[f49b3fc]	689	ast::ptr< ast::Type > t1_(t1);
	690	ast::ptr< ast::Type > t2_(t2);
[7870799]	691
[251ce80]	692	if ( unifyExact( t1, t2, env, need, have, open, widen ) ) {
[f474e91]	693	// if exact unification on unqualified types, try to merge qualifiers
	694	if ( q1 == q2 \|\| ( ( q1 > q2 \|\| widen.first ) && ( q2 > q1 \|\| widen.second ) ) ) {
[2890212]	695	t1->qualifiers = q1 \| q2;
	696	common = t1;
[f474e91]	697	return true;
	698	} else {
	699	return false;
	700	}
	701
[251ce80]	702	} else if (( common = commonType( t1, t2, env, need, have, open, widen ))) {
[f474e91]	703	// no exact unification, but common type
[2890212]	704	auto c = shallowCopy(common.get());
	705	c->qualifiers = q1 \| q2;
	706	common = c;
[f474e91]	707	return true;
	708	} else {
	709	return false;
	710	}
	711	}
	712
[54e41b3]	713	ast::ptr<ast::Type> extractResultType( const ast::FunctionType * func ) {
[4139e3d]	714	if ( func->returns.empty() ) return new ast::VoidType{};
[954c954]	715	if ( func->returns.size() == 1 ) return func->returns[0];
[4139e3d]	716
	717	std::vector<ast::ptr<ast::Type>> tys;
[954c954]	718	for ( const auto & decl : func->returns ) {
	719	tys.emplace_back( decl );
[4139e3d]	720	}
	721	return new ast::TupleType{ std::move(tys) };
[54e41b3]	722	}
[51b7345]	723	} // namespace ResolvExpr
[a32b204]	724
	725	// Local Variables: //
	726	// tab-width: 4 //
	727	// mode: c++ //
	728	// compile-command: "make install" //
	729	// End: //

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