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source: src/ResolvExpr/Unify.cc @ 2da12ae

Last change on this file since 2da12ae was c6b4432, checked in by Andrew Beach <ajbeach@…>, 12 months ago
Remove BaseSyntaxNode? and clean-up.
Property mode set to `100644`
File size: 23.8 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	if ( auto temp = dynamic_cast<const ast::EnumInstType *>(first) ) {
76	if ( !dynamic_cast< const ast::EnumInstType * >( second ) ) {
77	const ast::EnumDecl * baseEnum = dynamic_cast<const ast::EnumDecl *>(temp->base.get());
78	if ( auto t = baseEnum->base.get() ) {
79	newFirst = ast::shallowCopy( t );
80	}
81	}
82	} else if ( auto temp = dynamic_cast<const ast::EnumInstType *>(second) ) {
83	const ast::EnumDecl * baseEnum = dynamic_cast<const ast::EnumDecl *>(temp->base.get());
84	if ( auto t = baseEnum->base.get() ) {
85	newSecond = ast::shallowCopy( t );
86	}
87	}
88
89	newFirst ->qualifiers = {};
90	newSecond->qualifiers = {};
91	ast::ptr< ast::Type > t1_(newFirst );
92	ast::ptr< ast::Type > t2_(newSecond);
93
94	ast::ptr< ast::Type > subFirst = env.apply(newFirst).node;
95	ast::ptr< ast::Type > subSecond = env.apply(newSecond).node;
96
97	return unifyExact(
98	subFirst,
99	subSecond,
100	newEnv, need, have, open, noWiden() );
101	}
102
103	namespace {
104	/// Replaces ttype variables with their bound types.
105	/// If this isn't done when satifying ttype assertions, then argument lists can have
106	/// different size and structure when they should be compatible.
107	struct TtypeExpander_new : public ast::WithShortCircuiting, public ast::PureVisitor {
108	ast::TypeEnvironment & tenv;
109
110	TtypeExpander_new( ast::TypeEnvironment & env ) : tenv( env ) {}
111
112	const ast::Type * postvisit( const ast::TypeInstType * typeInst ) {
113	if ( const ast::EqvClass * clz = tenv.lookup( *typeInst ) ) {
114	// expand ttype parameter into its actual type
115	if ( clz->data.kind == ast::TypeDecl::Ttype && clz->bound ) {
116	return clz->bound;
117	}
118	}
119	return typeInst;
120	}
121	};
122	}
123
124	std::vector< ast::ptr< ast::Type > > flattenList(
125	const std::vector< ast::ptr< ast::Type > > & src, ast::TypeEnvironment & env
126	) {
127	std::vector< ast::ptr< ast::Type > > dst;
128	dst.reserve( src.size() );
129	for ( const auto & d : src ) {
130	ast::Pass<TtypeExpander_new> expander{ env };
131	// TtypeExpander pass is impure (may mutate nodes in place)
132	// need to make nodes shared to prevent accidental mutation
133	ast::ptr<ast::Type> dc = d->accept(expander);
134	auto types = flatten( dc );
135	for ( ast::ptr< ast::Type > & t : types ) {
136	// outermost const, volatile, _Atomic qualifiers in parameters should not play
137	// a role in the unification of function types, since they do not determine
138	// whether a function is callable.
139	// NOTE: must consider at least mutex qualifier, since functions can be
140	// overloaded on outermost mutex and a mutex function has different
141	// requirements than a non-mutex function
142	remove_qualifiers( t, ast::CV::Const \| ast::CV::Volatile \| ast::CV::Atomic );
143	dst.emplace_back( t );
144	}
145	}
146	return dst;
147	}
148
149	// Unification of Expressions
150	//
151	// Boolean outcome (obvious): Are they basically spelled the same?
152	// Side effect of binding variables (subtle): if `sizeof(int)` ===_expr `sizeof(T)` then `int` ===_ty `T`
153	//
154	// Context: if `float[VAREXPR1]` ===_ty `float[VAREXPR2]` then `VAREXPR1` ===_expr `VAREXPR2`
155	// where the VAREXPR are meant as notational metavariables representing the fact that unification always
156	// sees distinct ast::VariableExpr objects at these positions
157
158	static bool unify( const ast::Expr * e1, const ast::Expr * e2, ast::TypeEnvironment & env,
159	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open,
160	WidenMode widen );
161
162	class UnifyExpr final : public ast::WithShortCircuiting {
163	const ast::Expr * e2;
164	ast::TypeEnvironment & tenv;
165	ast::AssertionSet & need;
166	ast::AssertionSet & have;
167	const ast::OpenVarSet & open;
168	WidenMode widen;
169	public:
170	bool result;
171
172	private:
173
174	void tryMatchOnStaticValue( const ast::Expr * e1 ) {
175	Evaluation r1 = eval(e1);
176	Evaluation r2 = eval(e2);
177
178	if ( ! r1.hasKnownValue ) return;
179	if ( ! r2.hasKnownValue ) return;
180
181	if (r1.knownValue != r2.knownValue) return;
182
183	visit_children = false;
184	result = true;
185	}
186
187	public:
188
189	void previsit( const ast::Node * ) { assert(false); }
190
191	void previsit( const ast::Expr * e1 ) {
192	tryMatchOnStaticValue( e1 );
193	visit_children = false;
194	}
195
196	void previsit( const ast::CastExpr * e1 ) {
197	tryMatchOnStaticValue( e1 );
198
199	if (result) {
200	assert (visit_children == false);
201	} else {
202	assert (visit_children == true);
203	visit_children = false;
204
205	auto e2c = dynamic_cast< const ast::CastExpr * >( e2 );
206	if ( ! e2c ) return;
207
208	// inspect casts' target types
209	if ( ! unifyExact(
210	e1->result, e2c->result, tenv, need, have, open, widen ) ) return;
211
212	// inspect casts' inner expressions
213	result = unify( e1->arg, e2c->arg, tenv, need, have, open, widen );
214	}
215	}
216
217	void previsit( const ast::VariableExpr * e1 ) {
218	tryMatchOnStaticValue( e1 );
219
220	if (result) {
221	assert (visit_children == false);
222	} else {
223	assert (visit_children == true);
224	visit_children = false;
225
226	auto e2v = dynamic_cast< const ast::VariableExpr * >( e2 );
227	if ( ! e2v ) return;
228
229	assert(e1->var);
230	assert(e2v->var);
231
232	// conservative: variable exprs match if their declarations are represented by the same C++ AST object
233	result = (e1->var == e2v->var);
234	}
235	}
236
237	void previsit( const ast::SizeofExpr * e1 ) {
238	tryMatchOnStaticValue( e1 );
239
240	if (result) {
241	assert (visit_children == false);
242	} else {
243	assert (visit_children == true);
244	visit_children = false;
245
246	auto e2so = dynamic_cast< const ast::SizeofExpr * >( e2 );
247	if ( ! e2so ) return;
248
249	assert((e1->type != nullptr) ^ (e1->expr != nullptr));
250	assert((e2so->type != nullptr) ^ (e2so->expr != nullptr));
251	if ( ! (e1->type && e2so->type) ) return;
252
253	// expression unification calls type unification (mutual recursion)
254	result = unifyExact( e1->type, e2so->type, tenv, need, have, open, widen );
255	}
256	}
257
258	UnifyExpr( const ast::Expr * e2, ast::TypeEnvironment & env, ast::AssertionSet & need,
259	ast::AssertionSet & have, const ast::OpenVarSet & open, WidenMode widen )
260	: e2( e2 ), tenv(env), need(need), have(have), open(open), widen(widen), result(false) {}
261	};
262
263	static bool unify( const ast::Expr * e1, const ast::Expr * e2, ast::TypeEnvironment & env,
264	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open,
265	WidenMode widen ) {
266	assert( e1 && e2 );
267	return ast::Pass<UnifyExpr>::read( e1, e2, env, need, have, open, widen );
268	}
269
270	class Unify_new final : public ast::WithShortCircuiting {
271	const ast::Type * type2;
272	ast::TypeEnvironment & tenv;
273	ast::AssertionSet & need;
274	ast::AssertionSet & have;
275	const ast::OpenVarSet & open;
276	WidenMode widen;
277	public:
278	static size_t traceId;
279	bool result;
280
281	Unify_new(
282	const ast::Type * type2, ast::TypeEnvironment & env, ast::AssertionSet & need,
283	ast::AssertionSet & have, const ast::OpenVarSet & open, WidenMode widen )
284	: type2(type2), tenv(env), need(need), have(have), open(open), widen(widen),
285	result(false) {}
286
287	void previsit( const ast::Node * ) { visit_children = false; }
288
289	void postvisit( const ast::VoidType * ) {
290	result = dynamic_cast< const ast::VoidType * >( type2 );
291	}
292
293	void postvisit( const ast::BasicType * basic ) {
294	if ( auto basic2 = dynamic_cast< const ast::BasicType * >( type2 ) ) {
295	result = basic->kind == basic2->kind;
296	}
297	}
298
299	void postvisit( const ast::PointerType * pointer ) {
300	if ( auto pointer2 = dynamic_cast< const ast::PointerType * >( type2 ) ) {
301	result = unifyExact(
302	pointer->base, pointer2->base, tenv, need, have, open,
303	noWiden());
304	}
305	}
306
307	void postvisit( const ast::ArrayType * array ) {
308	auto array2 = dynamic_cast< const ast::ArrayType * >( type2 );
309	if ( ! array2 ) return;
310
311	if ( array->isVarLen != array2->isVarLen ) return;
312	if ( (array->dimension != nullptr) != (array2->dimension != nullptr) ) return;
313
314	if ( array->dimension ) {
315	assert( array2->dimension );
316	// type unification calls expression unification (mutual recursion)
317	if ( ! unify(array->dimension, array2->dimension,
318	tenv, need, have, open, widen) ) return;
319	}
320
321	result = unifyExact(
322	array->base, array2->base, tenv, need, have, open, noWiden());
323	}
324
325	void postvisit( const ast::ReferenceType * ref ) {
326	if ( auto ref2 = dynamic_cast< const ast::ReferenceType * >( type2 ) ) {
327	result = unifyExact(
328	ref->base, ref2->base, tenv, need, have, open, noWiden());
329	}
330	}
331
332	private:
333
334	template< typename Iter >
335	static bool unifyTypeList(
336	Iter crnt1, Iter end1, Iter crnt2, Iter end2, ast::TypeEnvironment & env,
337	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open
338	) {
339	while ( crnt1 != end1 && crnt2 != end2 ) {
340	const ast::Type * t1 = *crnt1;
341	const ast::Type * t2 = *crnt2;
342	bool isTuple1 = Tuples::isTtype( t1 );
343	bool isTuple2 = Tuples::isTtype( t2 );
344
345	// assumes here that ttype must be last parameter
346	if ( isTuple1 && ! isTuple2 ) {
347	// combine remainder of list2, then unify
348	return unifyExact(
349	t1, tupleFromTypes( crnt2, end2 ), env, need, have, open,
350	noWiden() );
351	} else if ( ! isTuple1 && isTuple2 ) {
352	// combine remainder of list1, then unify
353	return unifyExact(
354	tupleFromTypes( crnt1, end1 ), t2, env, need, have, open,
355	noWiden() );
356	}
357
358	if ( ! unifyExact(
359	t1, t2, env, need, have, open, noWiden() )
360	) return false;
361
362	++crnt1; ++crnt2;
363	}
364
365	// May get to the end of one argument list before the other. This is only okay if the
366	// other is a ttype
367	if ( crnt1 != end1 ) {
368	// try unifying empty tuple with ttype
369	const ast::Type * t1 = *crnt1;
370	if ( ! Tuples::isTtype( t1 ) ) return false;
371	return unifyExact(
372	t1, tupleFromTypes( crnt2, end2 ), env, need, have, open,
373	noWiden() );
374	} else if ( crnt2 != end2 ) {
375	// try unifying empty tuple with ttype
376	const ast::Type * t2 = *crnt2;
377	if ( ! Tuples::isTtype( t2 ) ) return false;
378	return unifyExact(
379	tupleFromTypes( crnt1, end1 ), t2, env, need, have, open,
380	noWiden() );
381	}
382
383	return true;
384	}
385
386	static bool unifyTypeList(
387	const std::vector< ast::ptr< ast::Type > > & list1,
388	const std::vector< ast::ptr< ast::Type > > & list2,
389	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
390	const ast::OpenVarSet & open
391	) {
392	return unifyTypeList(
393	list1.begin(), list1.end(), list2.begin(), list2.end(), env, need, have, open);
394	}
395
396	static void markAssertionSet( ast::AssertionSet & assns, const ast::VariableExpr * assn ) {
397	auto i = assns.find( assn );
398	if ( i != assns.end() ) {
399	i->second.isUsed = true;
400	}
401	}
402
403	/// mark all assertions in `type` used in both `assn1` and `assn2`
404	static void markAssertions(
405	ast::AssertionSet & assn1, ast::AssertionSet & assn2,
406	const ast::FunctionType * type
407	) {
408	for ( auto & assert : type->assertions ) {
409	markAssertionSet( assn1, assert );
410	markAssertionSet( assn2, assert );
411	}
412	}
413
414	public:
415	void postvisit( const ast::FunctionType * func ) {
416	auto func2 = dynamic_cast< const ast::FunctionType * >( type2 );
417	if ( ! func2 ) return;
418
419	if ( func->isVarArgs != func2->isVarArgs ) return;
420
421	// Flatten the parameter lists for both functions so that tuple structure does not
422	// affect unification. Does not actually mutate function parameters.
423	auto params = flattenList( func->params, tenv );
424	auto params2 = flattenList( func2->params, tenv );
425
426	// sizes don't have to match if ttypes are involved; need to be more precise w.r.t.
427	// where the ttype is to prevent errors
428	if (
429	( params.size() != params2.size() \|\| func->returns.size() != func2->returns.size() )
430	&& ! func->isTtype()
431	&& ! func2->isTtype()
432	) return;
433
434	if ( ! unifyTypeList( params, params2, tenv, need, have, open ) ) return;
435	if ( ! unifyTypeList(
436	func->returns, func2->returns, tenv, need, have, open ) ) return;
437
438	markAssertions( have, need, func );
439	markAssertions( have, need, func2 );
440
441	result = true;
442	}
443
444	private:
445	// Returns: other, cast as XInstType
446	// Assigns this->result: whether types are compatible (up to generic parameters)
447	template< typename XInstType >
448	const XInstType * handleRefType( const XInstType * inst, const ast::Type * other ) {
449	// check that the other type is compatible and named the same
450	auto otherInst = dynamic_cast< const XInstType * >( other );
451	if (otherInst && inst->name == otherInst->name)
452	this->result = otherInst;
453	return otherInst;
454	}
455
456	/// Creates a tuple type based on a list of TypeExpr
457	template< typename Iter >
458	static const ast::Type * tupleFromExprs(
459	const ast::TypeExpr * param, Iter & crnt, Iter end, ast::CV::Qualifiers qs
460	) {
461	std::vector< ast::ptr< ast::Type > > types;
462	do {
463	types.emplace_back( param->type );
464
465	++crnt;
466	if ( crnt == end ) break;
467	param = strict_dynamic_cast< const ast::TypeExpr * >( crnt->get() );
468	} while(true);
469
470	return new ast::TupleType{ std::move(types), qs };
471	}
472
473	template< typename XInstType >
474	void handleGenericRefType( const XInstType * inst, const ast::Type * other ) {
475	// check that other type is compatible and named the same
476	const XInstType * otherInst = handleRefType( inst, other );
477	if ( ! this->result ) return;
478
479	// check that parameters of types unify, if any
480	const std::vector< ast::ptr< ast::Expr > > & params = inst->params;
481	const std::vector< ast::ptr< ast::Expr > > & params2 = otherInst->params;
482
483	auto it = params.begin();
484	auto jt = params2.begin();
485	for ( ; it != params.end() && jt != params2.end(); ++it, ++jt ) {
486	auto param = strict_dynamic_cast< const ast::TypeExpr * >( it->get() );
487	auto param2 = strict_dynamic_cast< const ast::TypeExpr * >( jt->get() );
488
489	ast::ptr< ast::Type > pty = param->type;
490	ast::ptr< ast::Type > pty2 = param2->type;
491
492	bool isTuple = Tuples::isTtype( pty );
493	bool isTuple2 = Tuples::isTtype( pty2 );
494
495	if ( isTuple && isTuple2 ) {
496	++it; ++jt; // skip ttype parameters before break
497	} else if ( isTuple ) {
498	// bundle remaining params into tuple
499	pty2 = tupleFromExprs( param2, jt, params2.end(), pty->qualifiers );
500	++it; // skip ttype parameter for break
501	} else if ( isTuple2 ) {
502	// bundle remaining params into tuple
503	pty = tupleFromExprs( param, it, params.end(), pty2->qualifiers );
504	++jt; // skip ttype parameter for break
505	}
506
507	if ( ! unifyExact(
508	pty, pty2, tenv, need, have, open, noWiden() ) ) {
509	result = false;
510	return;
511	}
512
513	// ttype parameter should be last
514	if ( isTuple \|\| isTuple2 ) break;
515	}
516	result = it == params.end() && jt == params2.end();
517	}
518
519	public:
520	void postvisit( const ast::StructInstType * aggrType ) {
521	handleGenericRefType( aggrType, type2 );
522	}
523
524	void postvisit( const ast::UnionInstType * aggrType ) {
525	handleGenericRefType( aggrType, type2 );
526	}
527
528	void postvisit( const ast::EnumInstType * aggrType ) {
529	handleRefType( aggrType, type2 );
530	}
531
532	void postvisit( const ast::TraitInstType * aggrType ) {
533	handleRefType( aggrType, type2 );
534	}
535
536	void postvisit( const ast::TypeInstType * typeInst ) {
537	// assert( open.find( *typeInst ) == open.end() );
538	auto otherInst = dynamic_cast< const ast::TypeInstType * >( type2 );
539	if (otherInst && typeInst->name == otherInst->name)
540	this->result = otherInst;
541	// return otherInst;
542	}
543
544	private:
545	/// Creates a tuple type based on a list of Type
546
547	static bool unifyList(
548	const std::vector< ast::ptr< ast::Type > > & list1,
549	const std::vector< ast::ptr< ast::Type > > & list2, ast::TypeEnvironment & env,
550	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open
551	) {
552	auto crnt1 = list1.begin();
553	auto crnt2 = list2.begin();
554	while ( crnt1 != list1.end() && crnt2 != list2.end() ) {
555	const ast::Type * t1 = *crnt1;
556	const ast::Type * t2 = *crnt2;
557	bool isTuple1 = Tuples::isTtype( t1 );
558	bool isTuple2 = Tuples::isTtype( t2 );
559
560	// assumes ttype must be last parameter
561	if ( isTuple1 && ! isTuple2 ) {
562	// combine entirety of list2, then unify
563	return unifyExact(
564	t1, tupleFromTypes( list2 ), env, need, have, open,
565	noWiden() );
566	} else if ( ! isTuple1 && isTuple2 ) {
567	// combine entirety of list1, then unify
568	return unifyExact(
569	tupleFromTypes( list1 ), t2, env, need, have, open,
570	noWiden() );
571	}
572
573	if ( ! unifyExact(
574	t1, t2, env, need, have, open, noWiden() )
575	) return false;
576
577	++crnt1; ++crnt2;
578	}
579
580	if ( crnt1 != list1.end() ) {
581	// try unifying empty tuple type with ttype
582	const ast::Type * t1 = *crnt1;
583	if ( ! Tuples::isTtype( t1 ) ) return false;
584	// xxx - this doesn't generate an empty tuple, contrary to comment; both ported
585	// from Rob's code
586	return unifyExact(
587	t1, tupleFromTypes( list2 ), env, need, have, open,
588	noWiden() );
589	} else if ( crnt2 != list2.end() ) {
590	// try unifying empty tuple with ttype
591	const ast::Type * t2 = *crnt2;
592	if ( ! Tuples::isTtype( t2 ) ) return false;
593	// xxx - this doesn't generate an empty tuple, contrary to comment; both ported
594	// from Rob's code
595	return unifyExact(
596	tupleFromTypes( list1 ), t2, env, need, have, open,
597	noWiden() );
598	}
599
600	return true;
601	}
602
603	public:
604	void postvisit( const ast::TupleType * tuple ) {
605	auto tuple2 = dynamic_cast< const ast::TupleType * >( type2 );
606	if ( ! tuple2 ) return;
607
608	ast::Pass<TtypeExpander_new> expander{ tenv };
609
610	const ast::Type * flat = tuple->accept( expander );
611	const ast::Type * flat2 = tuple2->accept( expander );
612
613	auto types = flatten( flat );
614	auto types2 = flatten( flat2 );
615
616	result = unifyList( types, types2, tenv, need, have, open );
617	}
618
619	void postvisit( const ast::VarArgsType * ) {
620	result = dynamic_cast< const ast::VarArgsType * >( type2 );
621	}
622
623	void postvisit( const ast::ZeroType * ) {
624	result = dynamic_cast< const ast::ZeroType * >( type2 );
625	}
626
627	void postvisit( const ast::OneType * ) {
628	result = dynamic_cast< const ast::OneType * >( type2 );
629	}
630
631	private:
632	template< typename RefType > void handleRefType( RefType inst, Type other );
633	template< typename RefType > void handleGenericRefType( RefType inst, Type other );
634	};
635
636	// size_t Unify_new::traceId = Stats::Heap::new_stacktrace_id("Unify_new");
637	bool unify(
638	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
639	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
640	ast::OpenVarSet & open
641	) {
642	ast::ptr<ast::Type> common;
643	return unify( type1, type2, env, need, have, open, common );
644	}
645
646	bool unify(
647	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
648	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
649	ast::OpenVarSet & open, ast::ptr<ast::Type> & common
650	) {
651	ast::OpenVarSet closed;
652	// findOpenVars( type1, open, closed, need, have, FirstClosed );
653	findOpenVars( type2, open, closed, need, have, env, FirstOpen );
654	return unifyInexact(
655	type1, type2, env, need, have, open, WidenMode{ true, true }, common );
656	}
657
658	bool unifyExact(
659	const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env,
660	ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open,
661	WidenMode widen
662	) {
663	if ( type1->qualifiers != type2->qualifiers ) return false;
664
665	auto var1 = dynamic_cast< const ast::TypeInstType * >( type1 );
666	auto var2 = dynamic_cast< const ast::TypeInstType * >( type2 );
667	bool isopen1 = var1 && env.lookup(*var1);
668	bool isopen2 = var2 && env.lookup(*var2);
669
670	if ( isopen1 && isopen2 ) {
671	if ( var1->base->kind != var2->base->kind ) return false;
672	return env.bindVarToVar(
673	var1, var2, ast::TypeData{ var1->base->kind, var1->base->sized\|\|var2->base->sized }, need, have,
674	open, widen );
675	} else if ( isopen1 ) {
676	return env.bindVar( var1, type2, ast::TypeData{var1->base}, need, have, open, widen );
677	} else if ( isopen2 ) {
678	return env.bindVar( var2, type1, ast::TypeData{var2->base}, need, have, open, widen );
679	} else {
680	return ast::Pass<Unify_new>::read(
681	type1, type2, env, need, have, open, widen );
682	}
683	}
684
685	bool unifyInexact(
686	const ast::ptr<ast::Type> & type1, const ast::ptr<ast::Type> & type2,
687	ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have,
688	const ast::OpenVarSet & open, WidenMode widen,
689	ast::ptr<ast::Type> & common
690	) {
691	ast::CV::Qualifiers q1 = type1->qualifiers, q2 = type2->qualifiers;
692
693	// force t1 and t2 to be cloned if their qualifiers must be stripped, so that type1 and
694	// type2 are left unchanged; calling convention forces type{1,2}->strong_ref >= 1
695	ast::Type * t1 = shallowCopy(type1.get());
696	ast::Type * t2 = shallowCopy(type2.get());
697	t1->qualifiers = {};
698	t2->qualifiers = {};
699	ast::ptr< ast::Type > t1_(t1);
700	ast::ptr< ast::Type > t2_(t2);
701
702	if ( unifyExact( t1, t2, env, need, have, open, widen ) ) {
703	// if exact unification on unqualified types, try to merge qualifiers
704	if ( q1 == q2 \|\| ( ( q1 > q2 \|\| widen.first ) && ( q2 > q1 \|\| widen.second ) ) ) {
705	t1->qualifiers = q1 \| q2;
706	common = t1;
707	return true;
708	} else {
709	return false;
710	}
711
712	} else if (( common = commonType( t1, t2, env, need, have, open, widen ))) {
713	// no exact unification, but common type
714	auto c = shallowCopy(common.get());
715	c->qualifiers = q1 \| q2;
716	common = c;
717	return true;
718	} else {
719	return false;
720	}
721	}
722
723	ast::ptr<ast::Type> extractResultType( const ast::FunctionType * func ) {
724	if ( func->returns.empty() ) return new ast::VoidType{};
725	if ( func->returns.size() == 1 ) return func->returns[0];
726
727	std::vector<ast::ptr<ast::Type>> tys;
728	for ( const auto & decl : func->returns ) {
729	tys.emplace_back( decl );
730	}
731	return new ast::TupleType{ std::move(tys) };
732	}
733	} // namespace ResolvExpr
734
735	// Local Variables: //
736	// tab-width: 4 //
737	// mode: c++ //
738	// compile-command: "make install" //
739	// End: //

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