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source: src/ResolvExpr/Unify.cc @ 3f9a8d0

Last change on this file since 3f9a8d0 was 0522ebe, checked in by JiadaL <j82liang@…>, 3 months ago
Add EnumPosType? to type system
Property mode set to `100644`
File size: 23.2 KB

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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	//
7	// Unify.cc --
8	//
9	// Author : Richard C. Bilson
10	// Created On : Sun May 17 12:27:10 2015
11	// Last Modified By : Peter A. Buhr
12	// Last Modified On : Fri Dec 13 23:43:05 2019
13	// Update Count : 46
14	//
15
16	#include "Unify.h"
17
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
25	#include <vector>
26
27	#include "AST/Copy.hpp"
28	#include "AST/Decl.hpp"
29	#include "AST/Node.hpp"
30	#include "AST/Pass.hpp"
31	#include "AST/Print.hpp"
32	#include "AST/Type.hpp"
33	#include "AST/TypeEnvironment.hpp"
34	#include "Common/Eval.h" // for eval
35	#include "CommonType.hpp" // for commonType
36	#include "FindOpenVars.h" // for findOpenVars
37	#include "SpecCost.hpp" // for SpecCost
38	#include "Tuples/Tuples.h" // for isTtype
39	#include "typeops.h" // for flatten, occurs
40
41	namespace ast {
42	class SymbolTable;
43	}
44
45	// #define DEBUG
46
47	namespace ResolvExpr {
48
49	bool typesCompatible(
50	const ast::Type * first, const ast::Type * second,
51	const ast::TypeEnvironment & env ) {
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
60	// findOpenVars( newFirst, open, closed, need, have, FirstClosed );
61	findOpenVars( newSecond, open, closed, need, have, newEnv, FirstOpen );
62
63	return unifyExact(newFirst, newSecond, newEnv, need, have, open, noWiden() );
64	}
65
66	bool typesCompatibleIgnoreQualifiers(
67	const ast::Type * first, const ast::Type * second,
68	const ast::TypeEnvironment & env ) {
69	ast::TypeEnvironment newEnv;
70	ast::OpenVarSet open;
71	ast::AssertionSet need, have;
72
73	ast::Type * newFirst = shallowCopy( first );
74	ast::Type * newSecond = shallowCopy( second );
75
76	newFirst ->qualifiers = {};
77	newSecond->qualifiers = {};
78	ast::ptr< ast::Type > t1_(newFirst );
79	ast::ptr< ast::Type > t2_(newSecond);
80
81	ast::ptr< ast::Type > subFirst = env.apply(newFirst).node;
82	ast::ptr< ast::Type > subSecond = env.apply(newSecond).node;
83
84	return unifyExact(
85	subFirst,
86	subSecond,
87	newEnv, need, have, open, noWiden() );
88	}
89
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.
94	struct TtypeExpander : public ast::WithShortCircuiting, public ast::PureVisitor {
95	ast::TypeEnvironment & tenv;
96
97	TtypeExpander( ast::TypeEnvironment & env ) : tenv( env ) {}
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	}
110
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 ) {
117	ast::Pass<TtypeExpander> expander{ env };
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
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
257	class Unify final : public ast::WithShortCircuiting {
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:
265	static size_t traceId;
266	bool result;
267
268	Unify(
269	const ast::Type * type2, ast::TypeEnvironment & env, ast::AssertionSet & need,
270	ast::AssertionSet & have, const ast::OpenVarSet & open, WidenMode widen )
271	: type2(type2), tenv(env), need(need), have(have), open(open), widen(widen),
272	result(false) {}
273
274	void previsit( const ast::Node * ) { visit_children = false; }
275
276	void postvisit( const ast::VoidType * ) {
277	result = dynamic_cast< const ast::VoidType * >( type2 );
278	}
279
280	void postvisit( const ast::BasicType * basic ) {
281	if ( auto basic2 = dynamic_cast< const ast::BasicType * >( type2 ) ) {
282	result = basic->kind == basic2->kind;
283	}
284	}
285
286	void postvisit( const ast::PointerType * pointer ) {
287	if ( auto pointer2 = dynamic_cast< const ast::PointerType * >( type2 ) ) {
288	result = unifyExact(
289	pointer->base, pointer2->base, tenv, need, have, open,
290	noWiden());
291	}
292	}
293
294	void postvisit( const ast::ArrayType * array ) {
295	auto array2 = dynamic_cast< const ast::ArrayType * >( type2 );
296	if ( ! array2 ) return;
297
298	if ( array->isVarLen != array2->isVarLen ) return;
299	if ( (array->dimension != nullptr) != (array2->dimension != nullptr) ) return;
300
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;
306	}
307
308	result = unifyExact(
309	array->base, array2->base, tenv, need, have, open, noWiden());
310	}
311
312	void postvisit( const ast::ReferenceType * ref ) {
313	if ( auto ref2 = dynamic_cast< const ast::ReferenceType * >( type2 ) ) {
314	result = unifyExact(
315	ref->base, ref2->base, tenv, need, have, open, noWiden());
316	}
317	}
318
319	private:
320
321	template< typename Iter >
322	static bool unifyTypeList(
323	Iter crnt1, Iter end1, Iter crnt2, Iter end2, ast::TypeEnvironment & env,
324	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open
325	) {
326	while ( crnt1 != end1 && crnt2 != end2 ) {
327	const ast::Type * t1 = *crnt1;
328	const ast::Type * t2 = *crnt2;
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
335	return unifyExact(
336	t1, tupleFromTypes( crnt2, end2 ), env, need, have, open,
337	noWiden() );
338	} else if ( ! isTuple1 && isTuple2 ) {
339	// combine remainder of list1, then unify
340	return unifyExact(
341	tupleFromTypes( crnt1, end1 ), t2, env, need, have, open,
342	noWiden() );
343	}
344
345	if ( ! unifyExact(
346	t1, t2, env, need, have, open, noWiden() )
347	) return false;
348
349	++crnt1; ++crnt2;
350	}
351
352	// May get to the end of one argument list before the other. This is only okay if the
353	// other is a ttype
354	if ( crnt1 != end1 ) {
355	// try unifying empty tuple with ttype
356	const ast::Type * t1 = *crnt1;
357	if ( ! Tuples::isTtype( t1 ) ) return false;
358	return unifyExact(
359	t1, tupleFromTypes( crnt2, end2 ), env, need, have, open,
360	noWiden() );
361	} else if ( crnt2 != end2 ) {
362	// try unifying empty tuple with ttype
363	const ast::Type * t2 = *crnt2;
364	if ( ! Tuples::isTtype( t2 ) ) return false;
365	return unifyExact(
366	tupleFromTypes( crnt1, end1 ), t2, env, need, have, open,
367	noWiden() );
368	}
369
370	return true;
371	}
372
373	static bool unifyTypeList(
374	const std::vector< ast::ptr< ast::Type > > & list1,
375	const std::vector< ast::ptr< ast::Type > > & list2,
376	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
377	const ast::OpenVarSet & open
378	) {
379	return unifyTypeList(
380	list1.begin(), list1.end(), list2.begin(), list2.end(), env, need, have, open);
381	}
382
383	static void markAssertionSet( ast::AssertionSet & assns, const ast::VariableExpr * assn ) {
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`
391	static void markAssertions(
392	ast::AssertionSet & assn1, ast::AssertionSet & assn2,
393	const ast::FunctionType * type
394	) {
395	for ( auto & assert : type->assertions ) {
396	markAssertionSet( assn1, assert );
397	markAssertionSet( assn2, assert );
398	}
399	}
400
401	public:
402	void postvisit( const ast::FunctionType * func ) {
403	auto func2 = dynamic_cast< const ast::FunctionType * >( type2 );
404	if ( ! func2 ) return;
405
406	if ( func->isVarArgs != func2->isVarArgs ) return;
407
408	// Flatten the parameter lists for both functions so that tuple structure does not
409	// affect unification. Does not actually mutate function parameters.
410	auto params = flattenList( func->params, tenv );
411	auto params2 = flattenList( func2->params, tenv );
412
413	// sizes don't have to match if ttypes are involved; need to be more precise w.r.t.
414	// where the ttype is to prevent errors
415	if (
416	( params.size() != params2.size() \|\| func->returns.size() != func2->returns.size() )
417	&& ! func->isTtype()
418	&& ! func2->isTtype()
419	) return;
420
421	if ( ! unifyTypeList( params, params2, tenv, need, have, open ) ) return;
422	if ( ! unifyTypeList(
423	func->returns, func2->returns, tenv, need, have, open ) ) return;
424
425	markAssertions( have, need, func );
426	markAssertions( have, need, func2 );
427
428	result = true;
429	}
430
431	private:
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 ) {
436	// check that the other type is compatible and named the same
437	auto otherInst = dynamic_cast< const XInstType * >( other );
438	if (otherInst && inst->name == otherInst->name)
439	this->result = otherInst;
440	return otherInst;
441	}
442
443	/// Creates a tuple type based on a list of TypeExpr
444	template< typename Iter >
445	static const ast::Type * tupleFromExprs(
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
460	template< typename XInstType >
461	void handleGenericRefType( const XInstType * inst, const ast::Type * other ) {
462	// check that other type is compatible and named the same
463	const XInstType * otherInst = handleRefType( inst, other );
464	if ( ! this->result ) return;
465
466	// check that parameters of types unify, if any
467	const std::vector< ast::ptr< ast::Expr > > & params = inst->params;
468	const std::vector< ast::ptr< ast::Expr > > & params2 = otherInst->params;
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
484	} else if ( isTuple ) {
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
494	if ( ! unifyExact(
495	pty, pty2, tenv, need, have, open, noWiden() ) ) {
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:
507	void postvisit( const ast::StructInstType * aggrType ) {
508	handleGenericRefType( aggrType, type2 );
509	}
510
511	void postvisit( const ast::UnionInstType * aggrType ) {
512	handleGenericRefType( aggrType, type2 );
513	}
514
515	void postvisit( const ast::EnumInstType * aggrType ) {
516	handleRefType( aggrType, type2 );
517	}
518
519	void postvisit( const ast::EnumPosType * posType ) {
520	// Does nothing for now. Handled in ReplacePseudoFunc
521	// Might move here in the future
522	}
523
524	void postvisit( const ast::TraitInstType * aggrType ) {
525	handleRefType( aggrType, type2 );
526	}
527
528	void postvisit( const ast::TypeInstType * typeInst ) {
529	// assert( open.find( *typeInst ) == open.end() );
530	auto otherInst = dynamic_cast< const ast::TypeInstType * >( type2 );
531	if ( otherInst && typeInst->name == otherInst->name ) {
532	this->result = otherInst;
533	}
534	}
535
536	private:
537	/// Creates a tuple type based on a list of Type
538
539	static bool unifyList(
540	const std::vector< ast::ptr< ast::Type > > & list1,
541	const std::vector< ast::ptr< ast::Type > > & list2, ast::TypeEnvironment & env,
542	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open
543	) {
544	auto crnt1 = list1.begin();
545	auto crnt2 = list2.begin();
546	while ( crnt1 != list1.end() && crnt2 != list2.end() ) {
547	const ast::Type * t1 = *crnt1;
548	const ast::Type * t2 = *crnt2;
549	bool isTuple1 = Tuples::isTtype( t1 );
550	bool isTuple2 = Tuples::isTtype( t2 );
551
552	// assumes ttype must be last parameter
553	if ( isTuple1 && ! isTuple2 ) {
554	// combine entirety of list2, then unify
555	return unifyExact(
556	t1, tupleFromTypes( list2 ), env, need, have, open,
557	noWiden() );
558	} else if ( ! isTuple1 && isTuple2 ) {
559	// combine entirety of list1, then unify
560	return unifyExact(
561	tupleFromTypes( list1 ), t2, env, need, have, open,
562	noWiden() );
563	}
564
565	if ( ! unifyExact(
566	t1, t2, env, need, have, open, noWiden() )
567	) return false;
568
569	++crnt1; ++crnt2;
570	}
571
572	if ( crnt1 != list1.end() ) {
573	// try unifying empty tuple type with ttype
574	const ast::Type * t1 = *crnt1;
575	if ( ! Tuples::isTtype( t1 ) ) return false;
576	// xxx - this doesn't generate an empty tuple, contrary to comment; both ported
577	// from Rob's code
578	return unifyExact(
579	t1, tupleFromTypes( list2 ), env, need, have, open,
580	noWiden() );
581	} else if ( crnt2 != list2.end() ) {
582	// try unifying empty tuple with ttype
583	const ast::Type * t2 = *crnt2;
584	if ( ! Tuples::isTtype( t2 ) ) return false;
585	// xxx - this doesn't generate an empty tuple, contrary to comment; both ported
586	// from Rob's code
587	return unifyExact(
588	tupleFromTypes( list1 ), t2, env, need, have, open,
589	noWiden() );
590	}
591
592	return true;
593	}
594
595	public:
596	void postvisit( const ast::TupleType * tuple ) {
597	auto tuple2 = dynamic_cast< const ast::TupleType * >( type2 );
598	if ( ! tuple2 ) return;
599
600	ast::Pass<TtypeExpander> expander{ tenv };
601
602	const ast::Type * flat = tuple->accept( expander );
603	const ast::Type * flat2 = tuple2->accept( expander );
604
605	auto types = flatten( flat );
606	auto types2 = flatten( flat2 );
607
608	result = unifyList( types, types2, tenv, need, have, open );
609	}
610
611	void postvisit( const ast::VarArgsType * ) {
612	result = dynamic_cast< const ast::VarArgsType * >( type2 );
613	}
614
615	void postvisit( const ast::ZeroType * ) {
616	result = dynamic_cast< const ast::ZeroType * >( type2 );
617	}
618
619	void postvisit( const ast::OneType * ) {
620	result = dynamic_cast< const ast::OneType * >( type2 );
621	}
622	};
623
624	// size_t Unify::traceId = Stats::Heap::new_stacktrace_id("Unify");
625
626	bool unify(
627	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
628	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
629	ast::OpenVarSet & open
630	) {
631	ast::ptr<ast::Type> common;
632	return unify( type1, type2, env, need, have, open, common );
633	}
634
635	bool unify(
636	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
637	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
638	ast::OpenVarSet & open, ast::ptr<ast::Type> & common
639	) {
640	ast::OpenVarSet closed;
641	// findOpenVars( type1, open, closed, need, have, FirstClosed );
642	findOpenVars( type2, open, closed, need, have, env, FirstOpen );
643	return unifyInexact(
644	type1, type2, env, need, have, open, WidenMode{ true, true }, common );
645	}
646
647	bool unifyExact(
648	const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env,
649	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open,
650	WidenMode widen
651	) {
652	if ( type1->qualifiers != type2->qualifiers ) return false;
653
654	auto var1 = dynamic_cast< const ast::TypeInstType * >( type1 );
655	auto var2 = dynamic_cast< const ast::TypeInstType * >( type2 );
656	bool isopen1 = var1 && env.lookup(*var1);
657	bool isopen2 = var2 && env.lookup(*var2);
658
659	if ( isopen1 && isopen2 ) {
660	if ( var1->base->kind != var2->base->kind ) return false;
661	return env.bindVarToVar(
662	var1, var2, ast::TypeData{ var1->base->kind, var1->base->sized\|\|var2->base->sized }, need, have,
663	open, widen );
664	} else if ( isopen1 ) {
665	return env.bindVar( var1, type2, ast::TypeData{var1->base}, need, have, open, widen );
666	} else if ( isopen2 ) {
667	return env.bindVar( var2, type1, ast::TypeData{var2->base}, need, have, open, widen );
668	} else {
669	return ast::Pass<Unify>::read(
670	type1, type2, env, need, have, open, widen );
671	}
672	}
673
674	bool unifyInexact(
675	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
676	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
677	const ast::OpenVarSet & open, WidenMode widen,
678	ast::ptr<ast::Type> & common
679	) {
680	ast::CV::Qualifiers q1 = type1->qualifiers, q2 = type2->qualifiers;
681
682	// force t1 and t2 to be cloned if their qualifiers must be stripped, so that type1 and
683	// type2 are left unchanged; calling convention forces type{1,2}->strong_ref >= 1
684	ast::Type * t1 = shallowCopy(type1.get());
685	ast::Type * t2 = shallowCopy(type2.get());
686	t1->qualifiers = {};
687	t2->qualifiers = {};
688	ast::ptr< ast::Type > t1_(t1);
689	ast::ptr< ast::Type > t2_(t2);
690
691	if ( unifyExact( t1, t2, env, need, have, open, widen ) ) {
692	// if exact unification on unqualified types, try to merge qualifiers
693	if ( q1 == q2 \|\| ( ( q1 > q2 \|\| widen.first ) && ( q2 > q1 \|\| widen.second ) ) ) {
694	t1->qualifiers = q1 \| q2;
695	common = t1;
696	return true;
697	} else {
698	return false;
699	}
700
701	} else if (( common = commonType( t1, t2, env, need, have, open, widen ))) {
702	// no exact unification, but common type
703	auto c = shallowCopy(common.get());
704	c->qualifiers = q1 \| q2;
705	common = c;
706	return true;
707	} else {
708	return false;
709	}
710	}
711
712	ast::ptr<ast::Type> extractResultType( const ast::FunctionType * func ) {
713	if ( func->returns.empty() ) return new ast::VoidType{};
714	if ( func->returns.size() == 1 ) return func->returns[0];
715
716	std::vector<ast::ptr<ast::Type>> tys;
717	for ( const auto & decl : func->returns ) {
718	tys.emplace_back( decl );
719	}
720	return new ast::TupleType{ std::move(tys) };
721	}
722	} // namespace ResolvExpr
723
724	// Local Variables: //
725	// tab-width: 4 //
726	// mode: c++ //
727	// compile-command: "make install" //
728	// End: //

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