source: src/ResolvExpr/CandidateFinder.cpp@ 03c56f6

ADT ast-experimental
Last change on this file since 03c56f6 was 5408b59, checked in by JiadaL <j82liang@…>, 3 years ago

Remove var in QualifiedNameExpr
  • Property mode set to 100644
File size: 68.8 KB
Line 
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// CandidateFinder.cpp --
8//
9// Author : Aaron B. Moss
10// Created On : Wed Jun 5 14:30:00 2019
11// Last Modified By : Andrew Beach
12// Last Modified On : Wed Mar 16 11:58:00 2022
13// Update Count : 3
14//
15
16#include "CandidateFinder.hpp"
17
18#include <deque>
19#include <iterator> // for back_inserter
20#include <sstream>
21#include <string>
22#include <unordered_map>
23#include <vector>
24
25#include "Candidate.hpp"
26#include "CompilationState.h"
27#include "Cost.h"
28#include "ExplodedArg.hpp"
29#include "RenameVars.h" // for renameTyVars
30#include "Resolver.h"
31#include "ResolveTypeof.h"
32#include "SatisfyAssertions.hpp"
33#include "typeops.h" // for adjustExprType, conversionCost, polyCost, specCost
34#include "Unify.h"
35#include "AST/Expr.hpp"
36#include "AST/Node.hpp"
37#include "AST/Pass.hpp"
38#include "AST/Print.hpp"
39#include "AST/SymbolTable.hpp"
40#include "AST/Type.hpp"
41#include "Common/utility.h" // for move, copy
42#include "SymTab/Mangler.h"
43#include "Tuples/Tuples.h" // for handleTupleAssignment
44#include "InitTweak/InitTweak.h" // for getPointerBase
45
46#include "Common/Stats/Counter.h"
47
48#define PRINT( text ) if ( resolvep ) { text }
49
50namespace ResolvExpr {
51
52const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
53 if ( expr->result.as< ast::ReferenceType >() ) {
54 // cast away reference from expr
55 cost.incReference();
56 return new ast::CastExpr{ expr, expr->result->stripReferences() };
57 }
58
59 return expr;
60}
61
62/// Unique identifier for matching expression resolutions to their requesting expression
63UniqueId globalResnSlot = 0;
64
65Cost computeConversionCost(
66 const ast::Type * argType, const ast::Type * paramType, bool argIsLvalue,
67 const ast::SymbolTable & symtab, const ast::TypeEnvironment & env
68) {
69 PRINT(
70 std::cerr << std::endl << "converting ";
71 ast::print( std::cerr, argType, 2 );
72 std::cerr << std::endl << " to ";
73 ast::print( std::cerr, paramType, 2 );
74 std::cerr << std::endl << "environment is: ";
75 ast::print( std::cerr, env, 2 );
76 std::cerr << std::endl;
77 )
78 Cost convCost = conversionCost( argType, paramType, argIsLvalue, symtab, env );
79 PRINT(
80 std::cerr << std::endl << "cost is " << convCost << std::endl;
81 )
82 if ( convCost == Cost::infinity ) return convCost;
83 convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
84 PRINT(
85 std::cerr << "cost with polycost is " << convCost << std::endl;
86 )
87 return convCost;
88}
89
90namespace {
91 /// First index is which argument, second is which alternative, third is which exploded element
92 using ExplodedArgs_new = std::deque< std::vector< ExplodedArg > >;
93
94 /// Returns a list of alternatives with the minimum cost in the given list
95 CandidateList findMinCost( const CandidateList & candidates ) {
96 CandidateList out;
97 Cost minCost = Cost::infinity;
98 for ( const CandidateRef & r : candidates ) {
99 if ( r->cost < minCost ) {
100 minCost = r->cost;
101 out.clear();
102 out.emplace_back( r );
103 } else if ( r->cost == minCost ) {
104 out.emplace_back( r );
105 }
106 }
107 return out;
108 }
109
110 /// Computes conversion cost for a given expression to a given type
111 const ast::Expr * computeExpressionConversionCost(
112 const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost
113 ) {
114 Cost convCost = computeConversionCost(
115 arg->result, paramType, arg->get_lvalue(), symtab, env );
116 outCost += convCost;
117
118 // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires
119 // conversion. Ignore poly cost for now, since this requires resolution of the cast to
120 // infer parameters and this does not currently work for the reason stated below
121 Cost tmpCost = convCost;
122 tmpCost.incPoly( -tmpCost.get_polyCost() );
123 if ( tmpCost != Cost::zero ) {
124 ast::ptr< ast::Type > newType = paramType;
125 env.apply( newType );
126 return new ast::CastExpr{ arg, newType };
127
128 // xxx - *should* be able to resolve this cast, but at the moment pointers are not
129 // castable to zero_t, but are implicitly convertible. This is clearly inconsistent,
130 // once this is fixed it should be possible to resolve the cast.
131 // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable,
132 // but it shouldn't be because this makes the conversion from DT* to DT* since
133 // commontype(zero_t, DT*) is DT*, rather than nothing
134
135 // CandidateFinder finder{ symtab, env };
136 // finder.find( arg, ResolvMode::withAdjustment() );
137 // assertf( finder.candidates.size() > 0,
138 // "Somehow castable expression failed to find alternatives." );
139 // assertf( finder.candidates.size() == 1,
140 // "Somehow got multiple alternatives for known cast expression." );
141 // return finder.candidates.front()->expr;
142 }
143
144 return arg;
145 }
146
147 /// Computes conversion cost for a given candidate
148 Cost computeApplicationConversionCost(
149 CandidateRef cand, const ast::SymbolTable & symtab
150 ) {
151 auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
152 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
153 auto function = pointer->base.strict_as< ast::FunctionType >();
154
155 Cost convCost = Cost::zero;
156 const auto & params = function->params;
157 auto param = params.begin();
158 auto & args = appExpr->args;
159
160 for ( unsigned i = 0; i < args.size(); ++i ) {
161 const ast::Type * argType = args[i]->result;
162 PRINT(
163 std::cerr << "arg expression:" << std::endl;
164 ast::print( std::cerr, args[i], 2 );
165 std::cerr << "--- results are" << std::endl;
166 ast::print( std::cerr, argType, 2 );
167 )
168
169 if ( param == params.end() ) {
170 if ( function->isVarArgs ) {
171 convCost.incUnsafe();
172 PRINT( std::cerr << "end of params with varargs function: inc unsafe: "
173 << convCost << std::endl; ; )
174 // convert reference-typed expressions into value-typed expressions
175 cand->expr = ast::mutate_field_index(
176 appExpr, &ast::ApplicationExpr::args, i,
177 referenceToRvalueConversion( args[i], convCost ) );
178 continue;
179 } else return Cost::infinity;
180 }
181
182 if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
183 // Default arguments should be free - don't include conversion cost.
184 // Unwrap them here because they are not relevant to the rest of the system
185 cand->expr = ast::mutate_field_index(
186 appExpr, &ast::ApplicationExpr::args, i, def->expr );
187 ++param;
188 continue;
189 }
190
191 // mark conversion cost and also specialization cost of param type
192 // const ast::Type * paramType = (*param)->get_type();
193 cand->expr = ast::mutate_field_index(
194 appExpr, &ast::ApplicationExpr::args, i,
195 computeExpressionConversionCost(
196 args[i], *param, symtab, cand->env, convCost ) );
197 convCost.decSpec( specCost( *param ) );
198 ++param; // can't be in for-loop update because of the continue
199 }
200
201 if ( param != params.end() ) return Cost::infinity;
202
203 // specialization cost of return types can't be accounted for directly, it disables
204 // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
205 //
206 // forall(otype OS) {
207 // void ?|?(OS&, int); // with newline
208 // OS& ?|?(OS&, int); // no newline, always chosen due to more specialization
209 // }
210
211 // mark type variable and specialization cost of forall clause
212 convCost.incVar( function->forall.size() );
213 convCost.decSpec( function->assertions.size() );
214
215 return convCost;
216 }
217
218 void makeUnifiableVars(
219 const ast::FunctionType * type, ast::OpenVarSet & unifiableVars,
220 ast::AssertionSet & need
221 ) {
222 for ( auto & tyvar : type->forall ) {
223 unifiableVars[ *tyvar ] = ast::TypeDecl::Data{ tyvar->base };
224 }
225 for ( auto & assn : type->assertions ) {
226 need[ assn ].isUsed = true;
227 }
228 }
229
230 /// Gets a default value from an initializer, nullptr if not present
231 const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
232 if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
233 if ( auto ce = si->value.as< ast::CastExpr >() ) {
234 return ce->arg.as< ast::ConstantExpr >();
235 } else {
236 return si->value.as< ast::ConstantExpr >();
237 }
238 }
239 return nullptr;
240 }
241
242 /// State to iteratively build a match of parameter expressions to arguments
243 struct ArgPack {
244 std::size_t parent; ///< Index of parent pack
245 ast::ptr< ast::Expr > expr; ///< The argument stored here
246 Cost cost; ///< The cost of this argument
247 ast::TypeEnvironment env; ///< Environment for this pack
248 ast::AssertionSet need; ///< Assertions outstanding for this pack
249 ast::AssertionSet have; ///< Assertions found for this pack
250 ast::OpenVarSet open; ///< Open variables for this pack
251 unsigned nextArg; ///< Index of next argument in arguments list
252 unsigned tupleStart; ///< Number of tuples that start at this index
253 unsigned nextExpl; ///< Index of next exploded element
254 unsigned explAlt; ///< Index of alternative for nextExpl > 0
255
256 ArgPack()
257 : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ),
258 tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
259
260 ArgPack(
261 const ast::TypeEnvironment & env, const ast::AssertionSet & need,
262 const ast::AssertionSet & have, const ast::OpenVarSet & open )
263 : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ),
264 open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
265
266 ArgPack(
267 std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env,
268 ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open,
269 unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero,
270 unsigned nextExpl = 0, unsigned explAlt = 0 )
271 : parent(parent), expr( expr ), cost( cost ), env( std::move( env ) ), need( std::move( need ) ),
272 have( std::move( have ) ), open( std::move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
273 nextExpl( nextExpl ), explAlt( explAlt ) {}
274
275 ArgPack(
276 const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need,
277 ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
278 : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( std::move( env ) ),
279 need( std::move( need ) ), have( std::move( have ) ), open( std::move( open ) ), nextArg( nextArg ),
280 tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
281
282 /// true if this pack is in the middle of an exploded argument
283 bool hasExpl() const { return nextExpl > 0; }
284
285 /// Gets the list of exploded candidates for this pack
286 const ExplodedArg & getExpl( const ExplodedArgs_new & args ) const {
287 return args[ nextArg-1 ][ explAlt ];
288 }
289
290 /// Ends a tuple expression, consolidating the appropriate args
291 void endTuple( const std::vector< ArgPack > & packs ) {
292 // add all expressions in tuple to list, summing cost
293 std::deque< const ast::Expr * > exprs;
294 const ArgPack * pack = this;
295 if ( expr ) { exprs.emplace_front( expr ); }
296 while ( pack->tupleStart == 0 ) {
297 pack = &packs[pack->parent];
298 exprs.emplace_front( pack->expr );
299 cost += pack->cost;
300 }
301 // reset pack to appropriate tuple
302 std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
303 expr = new ast::TupleExpr{ expr->location, std::move( exprv ) };
304 tupleStart = pack->tupleStart - 1;
305 parent = pack->parent;
306 }
307 };
308
309 /// Instantiates an argument to match a parameter, returns false if no matching results left
310 bool instantiateArgument(
311 const ast::Type * paramType, const ast::Init * init, const ExplodedArgs_new & args,
312 std::vector< ArgPack > & results, std::size_t & genStart, const ast::SymbolTable & symtab,
313 unsigned nTuples = 0
314 ) {
315 if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
316 // paramType is a TupleType -- group args into a TupleExpr
317 ++nTuples;
318 for ( const ast::Type * type : *tupleType ) {
319 // xxx - dropping initializer changes behaviour from previous, but seems correct
320 // ^^^ need to handle the case where a tuple has a default argument
321 if ( ! instantiateArgument(
322 type, nullptr, args, results, genStart, symtab, nTuples ) ) return false;
323 nTuples = 0;
324 }
325 // re-constitute tuples for final generation
326 for ( auto i = genStart; i < results.size(); ++i ) {
327 results[i].endTuple( results );
328 }
329 return true;
330 } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
331 // paramType is a ttype, consumes all remaining arguments
332
333 // completed tuples; will be spliced to end of results to finish
334 std::vector< ArgPack > finalResults{};
335
336 // iterate until all results completed
337 std::size_t genEnd;
338 ++nTuples;
339 do {
340 genEnd = results.size();
341
342 // add another argument to results
343 for ( std::size_t i = genStart; i < genEnd; ++i ) {
344 unsigned nextArg = results[i].nextArg;
345
346 // use next element of exploded tuple if present
347 if ( results[i].hasExpl() ) {
348 const ExplodedArg & expl = results[i].getExpl( args );
349
350 unsigned nextExpl = results[i].nextExpl + 1;
351 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
352
353 results.emplace_back(
354 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
355 copy( results[i].need ), copy( results[i].have ),
356 copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
357 results[i].explAlt );
358
359 continue;
360 }
361
362 // finish result when out of arguments
363 if ( nextArg >= args.size() ) {
364 ArgPack newResult{
365 results[i].env, results[i].need, results[i].have, results[i].open };
366 newResult.nextArg = nextArg;
367 const ast::Type * argType = nullptr;
368
369 if ( nTuples > 0 || ! results[i].expr ) {
370 // first iteration or no expression to clone,
371 // push empty tuple expression
372 newResult.parent = i;
373 newResult.expr = new ast::TupleExpr{ CodeLocation{}, {} };
374 argType = newResult.expr->result;
375 } else {
376 // clone result to collect tuple
377 newResult.parent = results[i].parent;
378 newResult.cost = results[i].cost;
379 newResult.tupleStart = results[i].tupleStart;
380 newResult.expr = results[i].expr;
381 argType = newResult.expr->result;
382
383 if ( results[i].tupleStart > 0 && Tuples::isTtype( argType ) ) {
384 // the case where a ttype value is passed directly is special,
385 // e.g. for argument forwarding purposes
386 // xxx - what if passing multiple arguments, last of which is
387 // ttype?
388 // xxx - what would happen if unify was changed so that unifying
389 // tuple
390 // types flattened both before unifying lists? then pass in
391 // TupleType (ttype) below.
392 --newResult.tupleStart;
393 } else {
394 // collapse leftover arguments into tuple
395 newResult.endTuple( results );
396 argType = newResult.expr->result;
397 }
398 }
399
400 // check unification for ttype before adding to final
401 if (
402 unify(
403 ttype, argType, newResult.env, newResult.need, newResult.have,
404 newResult.open, symtab )
405 ) {
406 finalResults.emplace_back( std::move( newResult ) );
407 }
408
409 continue;
410 }
411
412 // add each possible next argument
413 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
414 const ExplodedArg & expl = args[nextArg][j];
415
416 // fresh copies of parent parameters for this iteration
417 ast::TypeEnvironment env = results[i].env;
418 ast::OpenVarSet open = results[i].open;
419
420 env.addActual( expl.env, open );
421
422 // skip empty tuple arguments by (nearly) cloning parent into next gen
423 if ( expl.exprs.empty() ) {
424 results.emplace_back(
425 results[i], std::move( env ), copy( results[i].need ),
426 copy( results[i].have ), std::move( open ), nextArg + 1, expl.cost );
427
428 continue;
429 }
430
431 // add new result
432 results.emplace_back(
433 i, expl.exprs.front(), std::move( env ), copy( results[i].need ),
434 copy( results[i].have ), std::move( open ), nextArg + 1, nTuples,
435 expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
436 }
437 }
438
439 // reset for next round
440 genStart = genEnd;
441 nTuples = 0;
442 } while ( genEnd != results.size() );
443
444 // splice final results onto results
445 for ( std::size_t i = 0; i < finalResults.size(); ++i ) {
446 results.emplace_back( std::move( finalResults[i] ) );
447 }
448 return ! finalResults.empty();
449 }
450
451 // iterate each current subresult
452 std::size_t genEnd = results.size();
453 for ( std::size_t i = genStart; i < genEnd; ++i ) {
454 unsigned nextArg = results[i].nextArg;
455
456 // use remainder of exploded tuple if present
457 if ( results[i].hasExpl() ) {
458 const ExplodedArg & expl = results[i].getExpl( args );
459 const ast::Expr * expr = expl.exprs[ results[i].nextExpl ];
460
461 ast::TypeEnvironment env = results[i].env;
462 ast::AssertionSet need = results[i].need, have = results[i].have;
463 ast::OpenVarSet open = results[i].open;
464
465 const ast::Type * argType = expr->result;
466
467 PRINT(
468 std::cerr << "param type is ";
469 ast::print( std::cerr, paramType );
470 std::cerr << std::endl << "arg type is ";
471 ast::print( std::cerr, argType );
472 std::cerr << std::endl;
473 )
474
475 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
476 unsigned nextExpl = results[i].nextExpl + 1;
477 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
478
479 results.emplace_back(
480 i, expr, std::move( env ), std::move( need ), std::move( have ), std::move( open ), nextArg,
481 nTuples, Cost::zero, nextExpl, results[i].explAlt );
482 }
483
484 continue;
485 }
486
487 // use default initializers if out of arguments
488 if ( nextArg >= args.size() ) {
489 if ( const ast::ConstantExpr * cnst = getDefaultValue( init ) ) {
490 ast::TypeEnvironment env = results[i].env;
491 ast::AssertionSet need = results[i].need, have = results[i].have;
492 ast::OpenVarSet open = results[i].open;
493
494 if ( unify( paramType, cnst->result, env, need, have, open, symtab ) ) {
495 results.emplace_back(
496 i, new ast::DefaultArgExpr{ cnst->location, cnst }, std::move( env ),
497 std::move( need ), std::move( have ), std::move( open ), nextArg, nTuples );
498 }
499 }
500
501 continue;
502 }
503
504 // Check each possible next argument
505 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
506 const ExplodedArg & expl = args[nextArg][j];
507
508 // fresh copies of parent parameters for this iteration
509 ast::TypeEnvironment env = results[i].env;
510 ast::AssertionSet need = results[i].need, have = results[i].have;
511 ast::OpenVarSet open = results[i].open;
512
513 env.addActual( expl.env, open );
514
515 // skip empty tuple arguments by (nearly) cloning parent into next gen
516 if ( expl.exprs.empty() ) {
517 results.emplace_back(
518 results[i], std::move( env ), std::move( need ), std::move( have ), std::move( open ),
519 nextArg + 1, expl.cost );
520
521 continue;
522 }
523
524 // consider only first exploded arg
525 const ast::Expr * expr = expl.exprs.front();
526 const ast::Type * argType = expr->result;
527
528 PRINT(
529 std::cerr << "param type is ";
530 ast::print( std::cerr, paramType );
531 std::cerr << std::endl << "arg type is ";
532 ast::print( std::cerr, argType );
533 std::cerr << std::endl;
534 )
535
536 // attempt to unify types
537 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
538 // add new result
539 results.emplace_back(
540 i, expr, std::move( env ), std::move( need ), std::move( have ), std::move( open ),
541 nextArg + 1, nTuples, expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
542 }
543 }
544 }
545
546 // reset for next parameter
547 genStart = genEnd;
548
549 return genEnd != results.size(); // were any new results added?
550 }
551
552 /// Generate a cast expression from `arg` to `toType`
553 const ast::Expr * restructureCast(
554 ast::ptr< ast::Expr > & arg, const ast::Type * toType, ast::GeneratedFlag isGenerated = ast::GeneratedCast
555 ) {
556 if (
557 arg->result->size() > 1
558 && ! toType->isVoid()
559 && ! dynamic_cast< const ast::ReferenceType * >( toType )
560 ) {
561 // Argument is a tuple and the target type is neither void nor a reference. Cast each
562 // member of the tuple to its corresponding target type, producing the tuple of those
563 // cast expressions. If there are more components of the tuple than components in the
564 // target type, then excess components do not come out in the result expression (but
565 // UniqueExpr ensures that the side effects will still be produced)
566 if ( Tuples::maybeImpureIgnoreUnique( arg ) ) {
567 // expressions which may contain side effects require a single unique instance of
568 // the expression
569 arg = new ast::UniqueExpr{ arg->location, arg };
570 }
571 std::vector< ast::ptr< ast::Expr > > components;
572 for ( unsigned i = 0; i < toType->size(); ++i ) {
573 // cast each component
574 ast::ptr< ast::Expr > idx = new ast::TupleIndexExpr{ arg->location, arg, i };
575 components.emplace_back(
576 restructureCast( idx, toType->getComponent( i ), isGenerated ) );
577 }
578 return new ast::TupleExpr{ arg->location, std::move( components ) };
579 } else {
580 // handle normally
581 return new ast::CastExpr{ arg->location, arg, toType, isGenerated };
582 }
583 }
584
585 /// Gets the name from an untyped member expression (must be NameExpr)
586 const std::string & getMemberName( const ast::UntypedMemberExpr * memberExpr ) {
587 if ( memberExpr->member.as< ast::ConstantExpr >() ) {
588 SemanticError( memberExpr, "Indexed access to struct fields unsupported: " );
589 }
590
591 return memberExpr->member.strict_as< ast::NameExpr >()->name;
592 }
593
594 /// Actually visits expressions to find their candidate interpretations
595 class Finder final : public ast::WithShortCircuiting {
596 const ResolveContext & context;
597 const ast::SymbolTable & symtab;
598 public:
599 // static size_t traceId;
600 CandidateFinder & selfFinder;
601 CandidateList & candidates;
602 const ast::TypeEnvironment & tenv;
603 ast::ptr< ast::Type > & targetType;
604
605 enum Errors {
606 NotFound,
607 NoMatch,
608 ArgsToFew,
609 ArgsToMany,
610 RetsToFew,
611 RetsToMany,
612 NoReason
613 };
614
615 struct {
616 Errors code = NotFound;
617 } reason;
618
619 Finder( CandidateFinder & f )
620 : context( f.context ), symtab( context.symtab ), selfFinder( f ),
621 candidates( f.candidates ), tenv( f.env ), targetType( f.targetType ) {}
622
623 void previsit( const ast::Node * ) { visit_children = false; }
624
625 /// Convenience to add candidate to list
626 template<typename... Args>
627 void addCandidate( Args &&... args ) {
628 candidates.emplace_back( new Candidate{ std::forward<Args>( args )... } );
629 reason.code = NoReason;
630 }
631
632 void postvisit( const ast::ApplicationExpr * applicationExpr ) {
633 addCandidate( applicationExpr, tenv );
634 }
635
636 /// Set up candidate assertions for inference
637 void inferParameters( CandidateRef & newCand, CandidateList & out ) {
638 // Set need bindings for any unbound assertions
639 UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
640 for ( auto & assn : newCand->need ) {
641 // skip already-matched assertions
642 if ( assn.second.resnSlot != 0 ) continue;
643 // assign slot for expression if needed
644 if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
645 // fix slot to assertion
646 assn.second.resnSlot = crntResnSlot;
647 }
648 // pair slot to expression
649 if ( crntResnSlot != 0 ) {
650 newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
651 }
652
653 // add to output list; assertion satisfaction will occur later
654 out.emplace_back( newCand );
655 }
656
657 /// Completes a function candidate with arguments located
658 void validateFunctionCandidate(
659 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
660 CandidateList & out
661 ) {
662 ast::ApplicationExpr * appExpr =
663 new ast::ApplicationExpr{ func->expr->location, func->expr };
664 // sum cost and accumulate arguments
665 std::deque< const ast::Expr * > args;
666 Cost cost = func->cost;
667 const ArgPack * pack = &result;
668 while ( pack->expr ) {
669 args.emplace_front( pack->expr );
670 cost += pack->cost;
671 pack = &results[pack->parent];
672 }
673 std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
674 appExpr->args = std::move( vargs );
675 // build and validate new candidate
676 auto newCand =
677 std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
678 PRINT(
679 std::cerr << "instantiate function success: " << appExpr << std::endl;
680 std::cerr << "need assertions:" << std::endl;
681 ast::print( std::cerr, result.need, 2 );
682 )
683 inferParameters( newCand, out );
684 }
685
686 /// Builds a list of candidates for a function, storing them in out
687 void makeFunctionCandidates(
688 const CandidateRef & func, const ast::FunctionType * funcType,
689 const ExplodedArgs_new & args, CandidateList & out
690 ) {
691 ast::OpenVarSet funcOpen;
692 ast::AssertionSet funcNeed, funcHave;
693 ast::TypeEnvironment funcEnv{ func->env };
694 makeUnifiableVars( funcType, funcOpen, funcNeed );
695 // add all type variables as open variables now so that those not used in the
696 // parameter list are still considered open
697 funcEnv.add( funcType->forall );
698
699 if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
700 // attempt to narrow based on expected target type
701 const ast::Type * returnType = funcType->returns.front();
702 if ( ! unify(
703 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, symtab )
704 ) {
705 // unification failed, do not pursue this candidate
706 return;
707 }
708 }
709
710 // iteratively build matches, one parameter at a time
711 std::vector< ArgPack > results;
712 results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
713 std::size_t genStart = 0;
714
715 // xxx - how to handle default arg after change to ftype representation?
716 if (const ast::VariableExpr * varExpr = func->expr.as<ast::VariableExpr>()) {
717 if (const ast::FunctionDecl * funcDecl = varExpr->var.as<ast::FunctionDecl>()) {
718 // function may have default args only if directly calling by name
719 // must use types on candidate however, due to RenameVars substitution
720 auto nParams = funcType->params.size();
721
722 for (size_t i=0; i<nParams; ++i) {
723 auto obj = funcDecl->params[i].strict_as<ast::ObjectDecl>();
724 if (!instantiateArgument(
725 funcType->params[i], obj->init, args, results, genStart, symtab)) return;
726 }
727 goto endMatch;
728 }
729 }
730 for ( const auto & param : funcType->params ) {
731 // Try adding the arguments corresponding to the current parameter to the existing
732 // matches
733 // no default args for indirect calls
734 if ( ! instantiateArgument(
735 param, nullptr, args, results, genStart, symtab ) ) return;
736 }
737
738 endMatch:
739 if ( funcType->isVarArgs ) {
740 // append any unused arguments to vararg pack
741 std::size_t genEnd;
742 do {
743 genEnd = results.size();
744
745 // iterate results
746 for ( std::size_t i = genStart; i < genEnd; ++i ) {
747 unsigned nextArg = results[i].nextArg;
748
749 // use remainder of exploded tuple if present
750 if ( results[i].hasExpl() ) {
751 const ExplodedArg & expl = results[i].getExpl( args );
752
753 unsigned nextExpl = results[i].nextExpl + 1;
754 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
755
756 results.emplace_back(
757 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
758 copy( results[i].need ), copy( results[i].have ),
759 copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
760 results[i].explAlt );
761
762 continue;
763 }
764
765 // finish result when out of arguments
766 if ( nextArg >= args.size() ) {
767 validateFunctionCandidate( func, results[i], results, out );
768
769 continue;
770 }
771
772 // add each possible next argument
773 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
774 const ExplodedArg & expl = args[nextArg][j];
775
776 // fresh copies of parent parameters for this iteration
777 ast::TypeEnvironment env = results[i].env;
778 ast::OpenVarSet open = results[i].open;
779
780 env.addActual( expl.env, open );
781
782 // skip empty tuple arguments by (nearly) cloning parent into next gen
783 if ( expl.exprs.empty() ) {
784 results.emplace_back(
785 results[i], std::move( env ), copy( results[i].need ),
786 copy( results[i].have ), std::move( open ), nextArg + 1,
787 expl.cost );
788
789 continue;
790 }
791
792 // add new result
793 results.emplace_back(
794 i, expl.exprs.front(), std::move( env ), copy( results[i].need ),
795 copy( results[i].have ), std::move( open ), nextArg + 1, 0, expl.cost,
796 expl.exprs.size() == 1 ? 0 : 1, j );
797 }
798 }
799
800 genStart = genEnd;
801 } while( genEnd != results.size() );
802 } else {
803 // filter out the results that don't use all the arguments
804 for ( std::size_t i = genStart; i < results.size(); ++i ) {
805 ArgPack & result = results[i];
806 if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
807 validateFunctionCandidate( func, result, results, out );
808 }
809 }
810 }
811 }
812
813 /// Adds implicit struct-conversions to the alternative list
814 void addAnonConversions( const CandidateRef & cand ) {
815 // adds anonymous member interpretations whenever an aggregate value type is seen.
816 // it's okay for the aggregate expression to have reference type -- cast it to the
817 // base type to treat the aggregate as the referenced value
818 ast::ptr< ast::Expr > aggrExpr( cand->expr );
819 ast::ptr< ast::Type > & aggrType = aggrExpr.get_and_mutate()->result;
820 cand->env.apply( aggrType );
821
822 if ( aggrType.as< ast::ReferenceType >() ) {
823 aggrExpr = new ast::CastExpr{ aggrExpr, aggrType->stripReferences() };
824 }
825
826 if ( auto structInst = aggrExpr->result.as< ast::StructInstType >() ) {
827 addAggMembers( structInst, aggrExpr, *cand, Cost::safe, "" );
828 } else if ( auto unionInst = aggrExpr->result.as< ast::UnionInstType >() ) {
829 addAggMembers( unionInst, aggrExpr, *cand, Cost::safe, "" );
830 }
831 }
832
833 /// Adds aggregate member interpretations
834 void addAggMembers(
835 const ast::BaseInstType * aggrInst, const ast::Expr * expr,
836 const Candidate & cand, const Cost & addedCost, const std::string & name
837 ) {
838 for ( const ast::Decl * decl : aggrInst->lookup( name ) ) {
839 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( decl );
840 CandidateRef newCand = std::make_shared<Candidate>(
841 cand, new ast::MemberExpr{ expr->location, dwt, expr }, addedCost );
842 // add anonymous member interpretations whenever an aggregate value type is seen
843 // as a member expression
844 addAnonConversions( newCand );
845 candidates.emplace_back( std::move( newCand ) );
846 }
847 }
848
849 /// Adds tuple member interpretations
850 void addTupleMembers(
851 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
852 const Cost & addedCost, const ast::Expr * member
853 ) {
854 if ( auto constantExpr = dynamic_cast< const ast::ConstantExpr * >( member ) ) {
855 // get the value of the constant expression as an int, must be between 0 and the
856 // length of the tuple to have meaning
857 long long val = constantExpr->intValue();
858 if ( val >= 0 && (unsigned long long)val < tupleType->size() ) {
859 addCandidate(
860 cand, new ast::TupleIndexExpr{ expr->location, expr, (unsigned)val },
861 addedCost );
862 }
863 }
864 }
865
866 void postvisit( const ast::UntypedExpr * untypedExpr ) {
867 std::vector< CandidateFinder > argCandidates =
868 selfFinder.findSubExprs( untypedExpr->args );
869
870 // take care of possible tuple assignments
871 // if not tuple assignment, handled as normal function call
872 Tuples::handleTupleAssignment( selfFinder, untypedExpr, argCandidates );
873
874 CandidateFinder funcFinder( context, tenv );
875 if (auto nameExpr = untypedExpr->func.as<ast::NameExpr>()) {
876 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
877 if (kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS) {
878 assertf(!argCandidates.empty(), "special function call without argument");
879 for (auto & firstArgCand: argCandidates[0]) {
880 ast::ptr<ast::Type> argType = firstArgCand->expr->result;
881 firstArgCand->env.apply(argType);
882 // strip references
883 // xxx - is this correct?
884 while (argType.as<ast::ReferenceType>()) argType = argType.as<ast::ReferenceType>()->base;
885
886 // convert 1-tuple to plain type
887 if (auto tuple = argType.as<ast::TupleType>()) {
888 if (tuple->size() == 1) {
889 argType = tuple->types[0];
890 }
891 }
892
893 // if argType is an unbound type parameter, all special functions need to be searched.
894 if (isUnboundType(argType)) {
895 funcFinder.otypeKeys.clear();
896 break;
897 }
898
899 if (argType.as<ast::PointerType>()) funcFinder.otypeKeys.insert(Mangle::Encoding::pointer);
900 // else if (const ast::EnumInstType * enumInst = argType.as<ast::EnumInstType>()) {
901 // const ast::EnumDecl * enumDecl = enumInst->base; // Here
902 // if ( const ast::Type* enumType = enumDecl->base ) {
903 // // instance of enum (T) is a instance of type (T)
904 // funcFinder.otypeKeys.insert(Mangle::mangle(enumType, Mangle::NoGenericParams | Mangle::Type));
905 // } else {
906 // // instance of an untyped enum is techically int
907 // funcFinder.otypeKeys.insert(Mangle::mangle(enumDecl, Mangle::NoGenericParams | Mangle::Type));
908 // }
909 // }
910 else funcFinder.otypeKeys.insert(Mangle::mangle(argType, Mangle::NoGenericParams | Mangle::Type));
911 }
912 }
913 }
914 // if candidates are already produced, do not fail
915 // xxx - is it possible that handleTupleAssignment and main finder both produce candidates?
916 // this means there exists ctor/assign functions with a tuple as first parameter.
917 ResolvMode mode = {
918 true, // adjust
919 !untypedExpr->func.as<ast::NameExpr>(), // prune if not calling by name
920 selfFinder.candidates.empty() // failfast if other options are not found
921 };
922 funcFinder.find( untypedExpr->func, mode );
923 // short-circuit if no candidates
924 // if ( funcFinder.candidates.empty() ) return;
925
926 reason.code = NoMatch;
927
928 // find function operators
929 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" }; // ??? why not ?{}
930 CandidateFinder opFinder( context, tenv );
931 // okay if there aren't any function operations
932 opFinder.find( opExpr, ResolvMode::withoutFailFast() );
933 PRINT(
934 std::cerr << "known function ops:" << std::endl;
935 print( std::cerr, opFinder.candidates, 1 );
936 )
937
938 // pre-explode arguments
939 ExplodedArgs_new argExpansions;
940 for ( const CandidateFinder & args : argCandidates ) {
941 argExpansions.emplace_back();
942 auto & argE = argExpansions.back();
943 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
944 }
945
946 // Find function matches
947 CandidateList found;
948 SemanticErrorException errors;
949 for ( CandidateRef & func : funcFinder ) {
950 try {
951 PRINT(
952 std::cerr << "working on alternative:" << std::endl;
953 print( std::cerr, *func, 2 );
954 )
955
956 // check if the type is a pointer to function
957 const ast::Type * funcResult = func->expr->result->stripReferences();
958 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
959 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
960 CandidateRef newFunc{ new Candidate{ *func } };
961 newFunc->expr =
962 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
963 makeFunctionCandidates( newFunc, function, argExpansions, found );
964 }
965 } else if (
966 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
967 ) {
968 if ( const ast::EqvClass * clz = func->env.lookup( *inst ) ) {
969 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
970 CandidateRef newFunc{ new Candidate{ *func } };
971 newFunc->expr =
972 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
973 makeFunctionCandidates( newFunc, function, argExpansions, found );
974 }
975 }
976 }
977 } catch ( SemanticErrorException & e ) { errors.append( e ); }
978 }
979
980 // Find matches on function operators `?()`
981 if ( ! opFinder.candidates.empty() ) {
982 // add exploded function alternatives to front of argument list
983 std::vector< ExplodedArg > funcE;
984 funcE.reserve( funcFinder.candidates.size() );
985 for ( const CandidateRef & func : funcFinder ) {
986 funcE.emplace_back( *func, symtab );
987 }
988 argExpansions.emplace_front( std::move( funcE ) );
989
990 for ( const CandidateRef & op : opFinder ) {
991 try {
992 // check if type is pointer-to-function
993 const ast::Type * opResult = op->expr->result->stripReferences();
994 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
995 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
996 CandidateRef newOp{ new Candidate{ *op} };
997 newOp->expr =
998 referenceToRvalueConversion( newOp->expr, newOp->cost );
999 makeFunctionCandidates( newOp, function, argExpansions, found );
1000 }
1001 }
1002 } catch ( SemanticErrorException & e ) { errors.append( e ); }
1003 }
1004 }
1005
1006 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
1007 // candidates
1008 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
1009
1010 // Compute conversion costs
1011 for ( CandidateRef & withFunc : found ) {
1012 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
1013
1014 PRINT(
1015 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
1016 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
1017 auto function = pointer->base.strict_as< ast::FunctionType >();
1018
1019 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
1020 std::cerr << "parameters are:" << std::endl;
1021 ast::printAll( std::cerr, function->params, 2 );
1022 std::cerr << "arguments are:" << std::endl;
1023 ast::printAll( std::cerr, appExpr->args, 2 );
1024 std::cerr << "bindings are:" << std::endl;
1025 ast::print( std::cerr, withFunc->env, 2 );
1026 std::cerr << "cost is: " << withFunc->cost << std::endl;
1027 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
1028 )
1029
1030 if ( cvtCost != Cost::infinity ) {
1031 withFunc->cvtCost = cvtCost;
1032 candidates.emplace_back( std::move( withFunc ) );
1033 }
1034 }
1035 found = std::move( candidates );
1036
1037 // use a new list so that candidates are not examined by addAnonConversions twice
1038 CandidateList winners = findMinCost( found );
1039 promoteCvtCost( winners );
1040
1041 // function may return a struct/union value, in which case we need to add candidates
1042 // for implicit conversions to each of the anonymous members, which must happen after
1043 // `findMinCost`, since anon conversions are never the cheapest
1044 for ( const CandidateRef & c : winners ) {
1045 addAnonConversions( c );
1046 }
1047 spliceBegin( candidates, winners );
1048
1049 if ( candidates.empty() && targetType && ! targetType->isVoid() ) {
1050 // If resolution is unsuccessful with a target type, try again without, since it
1051 // will sometimes succeed when it wouldn't with a target type binding.
1052 // For example:
1053 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
1054 // const char * x = "hello world";
1055 // unsigned char ch = x[0];
1056 // Fails with simple return type binding (xxx -- check this!) as follows:
1057 // * T is bound to unsigned char
1058 // * (x: const char *) is unified with unsigned char *, which fails
1059 // xxx -- fix this better
1060 targetType = nullptr;
1061 postvisit( untypedExpr );
1062 }
1063 }
1064
1065 /// true if expression is an lvalue
1066 static bool isLvalue( const ast::Expr * x ) {
1067 return x->result && ( x->get_lvalue() || x->result.as< ast::ReferenceType >() );
1068 }
1069
1070 void postvisit( const ast::AddressExpr * addressExpr ) {
1071 CandidateFinder finder( context, tenv );
1072 finder.find( addressExpr->arg );
1073
1074 if( finder.candidates.empty() ) return;
1075
1076 reason.code = NoMatch;
1077
1078 for ( CandidateRef & r : finder.candidates ) {
1079 if ( ! isLvalue( r->expr ) ) continue;
1080 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
1081 }
1082 }
1083
1084 void postvisit( const ast::LabelAddressExpr * labelExpr ) {
1085 addCandidate( labelExpr, tenv );
1086 }
1087
1088 void postvisit( const ast::CastExpr * castExpr ) {
1089 ast::ptr< ast::Type > toType = castExpr->result;
1090 assert( toType );
1091 toType = resolveTypeof( toType, context );
1092 toType = adjustExprType( toType, tenv, symtab );
1093
1094 CandidateFinder finder( context, tenv, toType );
1095 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1096
1097 if( !finder.candidates.empty() ) reason.code = NoMatch;
1098
1099 CandidateList matches;
1100 for ( CandidateRef & cand : finder.candidates ) {
1101 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1102 ast::OpenVarSet open( cand->open );
1103
1104 cand->env.extractOpenVars( open );
1105
1106 // It is possible that a cast can throw away some values in a multiply-valued
1107 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1108 // subexpression results that are cast directly. The candidate is invalid if it
1109 // has fewer results than there are types to cast to.
1110 int discardedValues = cand->expr->result->size() - toType->size();
1111 if ( discardedValues < 0 ) continue;
1112
1113 // unification run for side-effects
1114 unify( toType, cand->expr->result, cand->env, need, have, open, symtab );
1115 Cost thisCost =
1116 (castExpr->isGenerated == ast::GeneratedFlag::GeneratedCast)
1117 ? conversionCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env )
1118 : castCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env );
1119
1120 PRINT(
1121 std::cerr << "working on cast with result: " << toType << std::endl;
1122 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1123 std::cerr << "env: " << cand->env << std::endl;
1124 )
1125 if ( thisCost != Cost::infinity ) {
1126 PRINT(
1127 std::cerr << "has finite cost." << std::endl;
1128 )
1129 // count one safe conversion for each value that is thrown away
1130 thisCost.incSafe( discardedValues );
1131 CandidateRef newCand = std::make_shared<Candidate>(
1132 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1133 copy( cand->env ), std::move( open ), std::move( need ), cand->cost,
1134 cand->cost + thisCost );
1135 inferParameters( newCand, matches );
1136 }
1137 }
1138
1139 // select first on argument cost, then conversion cost
1140 CandidateList minArgCost = findMinCost( matches );
1141 promoteCvtCost( minArgCost );
1142 candidates = findMinCost( minArgCost );
1143 }
1144
1145 void postvisit( const ast::VirtualCastExpr * castExpr ) {
1146 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1147 CandidateFinder finder( context, tenv );
1148 // don't prune here, all alternatives guaranteed to have same type
1149 finder.find( castExpr->arg, ResolvMode::withoutPrune() );
1150 for ( CandidateRef & r : finder.candidates ) {
1151 addCandidate(
1152 *r,
1153 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
1154 }
1155 }
1156
1157 void postvisit( const ast::KeywordCastExpr * castExpr ) {
1158 const auto & loc = castExpr->location;
1159 assertf( castExpr->result, "Cast target should have been set in Validate." );
1160 auto ref = castExpr->result.strict_as<ast::ReferenceType>();
1161 auto inst = ref->base.strict_as<ast::StructInstType>();
1162 auto target = inst->base.get();
1163
1164 CandidateFinder finder( context, tenv );
1165
1166 auto pick_alternatives = [target, this](CandidateList & found, bool expect_ref) {
1167 for(auto & cand : found) {
1168 const ast::Type * expr = cand->expr->result.get();
1169 if(expect_ref) {
1170 auto res = dynamic_cast<const ast::ReferenceType*>(expr);
1171 if(!res) { continue; }
1172 expr = res->base.get();
1173 }
1174
1175 if(auto insttype = dynamic_cast<const ast::TypeInstType*>(expr)) {
1176 auto td = cand->env.lookup(*insttype);
1177 if(!td) { continue; }
1178 expr = td->bound.get();
1179 }
1180
1181 if(auto base = dynamic_cast<const ast::StructInstType*>(expr)) {
1182 if(base->base == target) {
1183 candidates.push_back( std::move(cand) );
1184 reason.code = NoReason;
1185 }
1186 }
1187 }
1188 };
1189
1190 try {
1191 // Attempt 1 : turn (thread&)X into (thread$&)X.__thrd
1192 // Clone is purely for memory management
1193 std::unique_ptr<const ast::Expr> tech1 { new ast::UntypedMemberExpr(loc, new ast::NameExpr(loc, castExpr->concrete_target.field), castExpr->arg) };
1194
1195 // don't prune here, since it's guaranteed all alternatives will have the same type
1196 finder.find( tech1.get(), ResolvMode::withoutPrune() );
1197 pick_alternatives(finder.candidates, false);
1198
1199 return;
1200 } catch(SemanticErrorException & ) {}
1201
1202 // Fallback : turn (thread&)X into (thread$&)get_thread(X)
1203 std::unique_ptr<const ast::Expr> fallback { ast::UntypedExpr::createDeref(loc, new ast::UntypedExpr(loc, new ast::NameExpr(loc, castExpr->concrete_target.getter), { castExpr->arg })) };
1204 // don't prune here, since it's guaranteed all alternatives will have the same type
1205 finder.find( fallback.get(), ResolvMode::withoutPrune() );
1206
1207 pick_alternatives(finder.candidates, true);
1208
1209 // Whatever happens here, we have no more fallbacks
1210 }
1211
1212 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
1213 CandidateFinder aggFinder( context, tenv );
1214 aggFinder.find( memberExpr->aggregate, ResolvMode::withAdjustment() );
1215 for ( CandidateRef & agg : aggFinder.candidates ) {
1216 // it's okay for the aggregate expression to have reference type -- cast it to the
1217 // base type to treat the aggregate as the referenced value
1218 Cost addedCost = Cost::zero;
1219 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1220
1221 // find member of the given type
1222 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1223 addAggMembers(
1224 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1225 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1226 addAggMembers(
1227 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1228 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1229 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1230 }
1231 }
1232 }
1233
1234 void postvisit( const ast::MemberExpr * memberExpr ) {
1235 addCandidate( memberExpr, tenv );
1236 }
1237
1238 void postvisit( const ast::NameExpr * nameExpr ) {
1239 std::vector< ast::SymbolTable::IdData > declList;
1240 if (!selfFinder.otypeKeys.empty()) {
1241 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
1242 assertf(kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS, "special lookup with non-special target: %s", nameExpr->name.c_str());
1243
1244 for (auto & otypeKey: selfFinder.otypeKeys) {
1245 auto result = symtab.specialLookupId(kind, otypeKey);
1246 declList.insert(declList.end(), std::make_move_iterator(result.begin()), std::make_move_iterator(result.end()));
1247 }
1248 }
1249 else {
1250 declList = symtab.lookupId( nameExpr->name );
1251 }
1252 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1253
1254 if( declList.empty() ) return;
1255
1256 reason.code = NoMatch;
1257
1258 for ( auto & data : declList ) {
1259 Cost cost = Cost::zero;
1260 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1261
1262 CandidateRef newCand = std::make_shared<Candidate>(
1263 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, Cost::zero,
1264 cost );
1265
1266 if (newCand->expr->env) {
1267 newCand->env.add(*newCand->expr->env);
1268 auto mutExpr = newCand->expr.get_and_mutate();
1269 mutExpr->env = nullptr;
1270 newCand->expr = mutExpr;
1271 }
1272
1273 PRINT(
1274 std::cerr << "decl is ";
1275 ast::print( std::cerr, data.id );
1276 std::cerr << std::endl;
1277 std::cerr << "newExpr is ";
1278 ast::print( std::cerr, newExpr );
1279 std::cerr << std::endl;
1280 )
1281 newCand->expr = ast::mutate_field(
1282 newCand->expr.get(), &ast::Expr::result,
1283 renameTyVars( newCand->expr->result ) );
1284 // add anonymous member interpretations whenever an aggregate value type is seen
1285 // as a name expression
1286 addAnonConversions( newCand );
1287 candidates.emplace_back( std::move( newCand ) );
1288 }
1289 }
1290
1291 void postvisit( const ast::VariableExpr * variableExpr ) {
1292 // not sufficient to just pass `variableExpr` here, type might have changed since
1293 // creation
1294 addCandidate(
1295 new ast::VariableExpr{ variableExpr->location, variableExpr->var }, tenv );
1296 }
1297
1298 void postvisit( const ast::ConstantExpr * constantExpr ) {
1299 addCandidate( constantExpr, tenv );
1300 }
1301
1302 void postvisit( const ast::SizeofExpr * sizeofExpr ) {
1303 if ( sizeofExpr->type ) {
1304 addCandidate(
1305 new ast::SizeofExpr{
1306 sizeofExpr->location, resolveTypeof( sizeofExpr->type, context ) },
1307 tenv );
1308 } else {
1309 // find all candidates for the argument to sizeof
1310 CandidateFinder finder( context, tenv );
1311 finder.find( sizeofExpr->expr );
1312 // find the lowest-cost candidate, otherwise ambiguous
1313 CandidateList winners = findMinCost( finder.candidates );
1314 if ( winners.size() != 1 ) {
1315 SemanticError(
1316 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1317 }
1318 // return the lowest-cost candidate
1319 CandidateRef & choice = winners.front();
1320 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1321 choice->cost = Cost::zero;
1322 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1323 }
1324 }
1325
1326 void postvisit( const ast::AlignofExpr * alignofExpr ) {
1327 if ( alignofExpr->type ) {
1328 addCandidate(
1329 new ast::AlignofExpr{
1330 alignofExpr->location, resolveTypeof( alignofExpr->type, context ) },
1331 tenv );
1332 } else {
1333 // find all candidates for the argument to alignof
1334 CandidateFinder finder( context, tenv );
1335 finder.find( alignofExpr->expr );
1336 // find the lowest-cost candidate, otherwise ambiguous
1337 CandidateList winners = findMinCost( finder.candidates );
1338 if ( winners.size() != 1 ) {
1339 SemanticError(
1340 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1341 }
1342 // return the lowest-cost candidate
1343 CandidateRef & choice = winners.front();
1344 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1345 choice->cost = Cost::zero;
1346 addCandidate(
1347 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1348 }
1349 }
1350
1351 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
1352 const ast::BaseInstType * aggInst;
1353 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1354 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1355 else return;
1356
1357 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1358 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1359 addCandidate(
1360 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1361 }
1362 }
1363
1364 void postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1365 addCandidate( offsetofExpr, tenv );
1366 }
1367
1368 void postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1369 addCandidate( offsetPackExpr, tenv );
1370 }
1371
1372 void postvisit( const ast::LogicalExpr * logicalExpr ) {
1373 CandidateFinder finder1( context, tenv );
1374 finder1.find( logicalExpr->arg1, ResolvMode::withAdjustment() );
1375 if ( finder1.candidates.empty() ) return;
1376
1377 CandidateFinder finder2( context, tenv );
1378 finder2.find( logicalExpr->arg2, ResolvMode::withAdjustment() );
1379 if ( finder2.candidates.empty() ) return;
1380
1381 reason.code = NoMatch;
1382
1383 for ( const CandidateRef & r1 : finder1.candidates ) {
1384 for ( const CandidateRef & r2 : finder2.candidates ) {
1385 ast::TypeEnvironment env{ r1->env };
1386 env.simpleCombine( r2->env );
1387 ast::OpenVarSet open{ r1->open };
1388 mergeOpenVars( open, r2->open );
1389 ast::AssertionSet need;
1390 mergeAssertionSet( need, r1->need );
1391 mergeAssertionSet( need, r2->need );
1392
1393 addCandidate(
1394 new ast::LogicalExpr{
1395 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
1396 std::move( env ), std::move( open ), std::move( need ), r1->cost + r2->cost );
1397 }
1398 }
1399 }
1400
1401 void postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1402 // candidates for condition
1403 CandidateFinder finder1( context, tenv );
1404 finder1.find( conditionalExpr->arg1, ResolvMode::withAdjustment() );
1405 if ( finder1.candidates.empty() ) return;
1406
1407 // candidates for true result
1408 CandidateFinder finder2( context, tenv );
1409 finder2.find( conditionalExpr->arg2, ResolvMode::withAdjustment() );
1410 if ( finder2.candidates.empty() ) return;
1411
1412 // candidates for false result
1413 CandidateFinder finder3( context, tenv );
1414 finder3.find( conditionalExpr->arg3, ResolvMode::withAdjustment() );
1415 if ( finder3.candidates.empty() ) return;
1416
1417 reason.code = NoMatch;
1418
1419 for ( const CandidateRef & r1 : finder1.candidates ) {
1420 for ( const CandidateRef & r2 : finder2.candidates ) {
1421 for ( const CandidateRef & r3 : finder3.candidates ) {
1422 ast::TypeEnvironment env{ r1->env };
1423 env.simpleCombine( r2->env );
1424 env.simpleCombine( r3->env );
1425 ast::OpenVarSet open{ r1->open };
1426 mergeOpenVars( open, r2->open );
1427 mergeOpenVars( open, r3->open );
1428 ast::AssertionSet need;
1429 mergeAssertionSet( need, r1->need );
1430 mergeAssertionSet( need, r2->need );
1431 mergeAssertionSet( need, r3->need );
1432 ast::AssertionSet have;
1433
1434 // unify true and false results, then infer parameters to produce new
1435 // candidates
1436 ast::ptr< ast::Type > common;
1437 if (
1438 unify(
1439 r2->expr->result, r3->expr->result, env, need, have, open, symtab,
1440 common )
1441 ) {
1442 // generate typed expression
1443 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1444 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1445 newExpr->result = common ? common : r2->expr->result;
1446 // convert both options to result type
1447 Cost cost = r1->cost + r2->cost + r3->cost;
1448 newExpr->arg2 = computeExpressionConversionCost(
1449 newExpr->arg2, newExpr->result, symtab, env, cost );
1450 newExpr->arg3 = computeExpressionConversionCost(
1451 newExpr->arg3, newExpr->result, symtab, env, cost );
1452 // output candidate
1453 CandidateRef newCand = std::make_shared<Candidate>(
1454 newExpr, std::move( env ), std::move( open ), std::move( need ), cost );
1455 inferParameters( newCand, candidates );
1456 }
1457 }
1458 }
1459 }
1460 }
1461
1462 void postvisit( const ast::CommaExpr * commaExpr ) {
1463 ast::TypeEnvironment env{ tenv };
1464 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, context, env );
1465
1466 CandidateFinder finder2( context, env );
1467 finder2.find( commaExpr->arg2, ResolvMode::withAdjustment() );
1468
1469 for ( const CandidateRef & r2 : finder2.candidates ) {
1470 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1471 }
1472 }
1473
1474 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1475 addCandidate( ctorExpr, tenv );
1476 }
1477
1478 void postvisit( const ast::ConstructorExpr * ctorExpr ) {
1479 CandidateFinder finder( context, tenv );
1480 finder.find( ctorExpr->callExpr, ResolvMode::withoutPrune() );
1481 for ( CandidateRef & r : finder.candidates ) {
1482 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1483 }
1484 }
1485
1486 void postvisit( const ast::RangeExpr * rangeExpr ) {
1487 // resolve low and high, accept candidates where low and high types unify
1488 CandidateFinder finder1( context, tenv );
1489 finder1.find( rangeExpr->low, ResolvMode::withAdjustment() );
1490 if ( finder1.candidates.empty() ) return;
1491
1492 CandidateFinder finder2( context, tenv );
1493 finder2.find( rangeExpr->high, ResolvMode::withAdjustment() );
1494 if ( finder2.candidates.empty() ) return;
1495
1496 reason.code = NoMatch;
1497
1498 for ( const CandidateRef & r1 : finder1.candidates ) {
1499 for ( const CandidateRef & r2 : finder2.candidates ) {
1500 ast::TypeEnvironment env{ r1->env };
1501 env.simpleCombine( r2->env );
1502 ast::OpenVarSet open{ r1->open };
1503 mergeOpenVars( open, r2->open );
1504 ast::AssertionSet need;
1505 mergeAssertionSet( need, r1->need );
1506 mergeAssertionSet( need, r2->need );
1507 ast::AssertionSet have;
1508
1509 ast::ptr< ast::Type > common;
1510 if (
1511 unify(
1512 r1->expr->result, r2->expr->result, env, need, have, open, symtab,
1513 common )
1514 ) {
1515 // generate new expression
1516 ast::RangeExpr * newExpr =
1517 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1518 newExpr->result = common ? common : r1->expr->result;
1519 // add candidate
1520 CandidateRef newCand = std::make_shared<Candidate>(
1521 newExpr, std::move( env ), std::move( open ), std::move( need ),
1522 r1->cost + r2->cost );
1523 inferParameters( newCand, candidates );
1524 }
1525 }
1526 }
1527 }
1528
1529 void postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1530 std::vector< CandidateFinder > subCandidates =
1531 selfFinder.findSubExprs( tupleExpr->exprs );
1532 std::vector< CandidateList > possibilities;
1533 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1534
1535 for ( const CandidateList & subs : possibilities ) {
1536 std::vector< ast::ptr< ast::Expr > > exprs;
1537 exprs.reserve( subs.size() );
1538 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1539
1540 ast::TypeEnvironment env;
1541 ast::OpenVarSet open;
1542 ast::AssertionSet need;
1543 for ( const CandidateRef & sub : subs ) {
1544 env.simpleCombine( sub->env );
1545 mergeOpenVars( open, sub->open );
1546 mergeAssertionSet( need, sub->need );
1547 }
1548
1549 addCandidate(
1550 new ast::TupleExpr{ tupleExpr->location, std::move( exprs ) },
1551 std::move( env ), std::move( open ), std::move( need ), sumCost( subs ) );
1552 }
1553 }
1554
1555 void postvisit( const ast::TupleExpr * tupleExpr ) {
1556 addCandidate( tupleExpr, tenv );
1557 }
1558
1559 void postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1560 addCandidate( tupleExpr, tenv );
1561 }
1562
1563 void postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1564 addCandidate( tupleExpr, tenv );
1565 }
1566
1567 void postvisit( const ast::UniqueExpr * unqExpr ) {
1568 CandidateFinder finder( context, tenv );
1569 finder.find( unqExpr->expr, ResolvMode::withAdjustment() );
1570 for ( CandidateRef & r : finder.candidates ) {
1571 // ensure that the the id is passed on so that the expressions are "linked"
1572 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1573 }
1574 }
1575
1576 void postvisit( const ast::StmtExpr * stmtExpr ) {
1577 addCandidate( resolveStmtExpr( stmtExpr, context ), tenv );
1578 }
1579
1580 void postvisit( const ast::UntypedInitExpr * initExpr ) {
1581 // handle each option like a cast
1582 CandidateList matches;
1583 PRINT(
1584 std::cerr << "untyped init expr: " << initExpr << std::endl;
1585 )
1586 // O(n^2) checks of d-types with e-types
1587 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1588 // calculate target type
1589 const ast::Type * toType = resolveTypeof( initAlt.type, context );
1590 toType = adjustExprType( toType, tenv, symtab );
1591 // The call to find must occur inside this loop, otherwise polymorphic return
1592 // types are not bound to the initialization type, since return type variables are
1593 // only open for the duration of resolving the UntypedExpr.
1594 CandidateFinder finder( context, tenv, toType );
1595 finder.find( initExpr->expr, ResolvMode::withAdjustment() );
1596 for ( CandidateRef & cand : finder.candidates ) {
1597 if(reason.code == NotFound) reason.code = NoMatch;
1598
1599 ast::TypeEnvironment env{ cand->env };
1600 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1601 ast::OpenVarSet open{ cand->open };
1602
1603 PRINT(
1604 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1605 )
1606
1607 // It is possible that a cast can throw away some values in a multiply-valued
1608 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1609 // the subexpression results that are cast directly. The candidate is invalid
1610 // if it has fewer results than there are types to cast to.
1611 int discardedValues = cand->expr->result->size() - toType->size();
1612 if ( discardedValues < 0 ) continue;
1613
1614 // unification run for side-effects
1615 bool canUnify = unify( toType, cand->expr->result, env, need, have, open, symtab );
1616 (void) canUnify;
1617 Cost thisCost = computeConversionCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1618 symtab, env );
1619 PRINT(
1620 Cost legacyCost = castCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1621 symtab, env );
1622 std::cerr << "Considering initialization:";
1623 std::cerr << std::endl << " FROM: " << cand->expr->result << std::endl;
1624 std::cerr << std::endl << " TO: " << toType << std::endl;
1625 std::cerr << std::endl << " Unification " << (canUnify ? "succeeded" : "failed");
1626 std::cerr << std::endl << " Legacy cost " << legacyCost;
1627 std::cerr << std::endl << " New cost " << thisCost;
1628 std::cerr << std::endl;
1629 )
1630 if ( thisCost != Cost::infinity ) {
1631 // count one safe conversion for each value that is thrown away
1632 thisCost.incSafe( discardedValues );
1633 CandidateRef newCand = std::make_shared<Candidate>(
1634 new ast::InitExpr{
1635 initExpr->location, restructureCast( cand->expr, toType ),
1636 initAlt.designation },
1637 std::move(env), std::move( open ), std::move( need ), cand->cost, thisCost );
1638 inferParameters( newCand, matches );
1639 }
1640 }
1641
1642 }
1643
1644 // select first on argument cost, then conversion cost
1645 CandidateList minArgCost = findMinCost( matches );
1646 promoteCvtCost( minArgCost );
1647 candidates = findMinCost( minArgCost );
1648 }
1649
1650 void postvisit( const ast::InitExpr * ) {
1651 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1652 }
1653
1654 void postvisit( const ast::DeletedExpr * ) {
1655 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1656 }
1657
1658 void postvisit( const ast::GenericExpr * ) {
1659 assertf( false, "_Generic is not yet supported." );
1660 }
1661 };
1662
1663 // size_t Finder::traceId = Stats::Heap::new_stacktrace_id("Finder");
1664 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1665 /// return type. Skips ambiguous candidates.
1666
1667} // anonymous namespace
1668
1669bool CandidateFinder::pruneCandidates( CandidateList & candidates, CandidateList & out, std::vector<std::string> & errors ) {
1670 struct PruneStruct {
1671 CandidateRef candidate;
1672 bool ambiguous;
1673
1674 PruneStruct() = default;
1675 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1676 };
1677
1678 // find lowest-cost candidate for each type
1679 std::unordered_map< std::string, PruneStruct > selected;
1680 // attempt to skip satisfyAssertions on more expensive alternatives if better options have been found
1681 std::sort(candidates.begin(), candidates.end(), [](const CandidateRef & x, const CandidateRef & y){return x->cost < y->cost;});
1682 for ( CandidateRef & candidate : candidates ) {
1683 std::string mangleName;
1684 {
1685 ast::ptr< ast::Type > newType = candidate->expr->result;
1686 assertf(candidate->expr->result, "Result of expression %p for candidate is null", candidate->expr.get());
1687 candidate->env.apply( newType );
1688 mangleName = Mangle::mangle( newType );
1689 }
1690
1691 auto found = selected.find( mangleName );
1692 if (found != selected.end() && found->second.candidate->cost < candidate->cost) {
1693 PRINT(
1694 std::cerr << "cost " << candidate->cost << " loses to "
1695 << found->second.candidate->cost << std::endl;
1696 )
1697 continue;
1698 }
1699
1700 // xxx - when do satisfyAssertions produce more than 1 result?
1701 // this should only happen when initial result type contains
1702 // unbound type parameters, then it should never be pruned by
1703 // the previous step, since renameTyVars guarantees the mangled name
1704 // is unique.
1705 CandidateList satisfied;
1706 bool needRecomputeKey = false;
1707 if (candidate->need.empty()) {
1708 satisfied.emplace_back(candidate);
1709 }
1710 else {
1711 satisfyAssertions(candidate, context.symtab, satisfied, errors);
1712 needRecomputeKey = true;
1713 }
1714
1715 for (auto & newCand : satisfied) {
1716 // recomputes type key, if satisfyAssertions changed it
1717 if (needRecomputeKey)
1718 {
1719 ast::ptr< ast::Type > newType = newCand->expr->result;
1720 assertf(newCand->expr->result, "Result of expression %p for candidate is null", newCand->expr.get());
1721 newCand->env.apply( newType );
1722 mangleName = Mangle::mangle( newType );
1723 }
1724 auto found = selected.find( mangleName );
1725 if ( found != selected.end() ) {
1726 if ( newCand->cost < found->second.candidate->cost ) {
1727 PRINT(
1728 std::cerr << "cost " << newCand->cost << " beats "
1729 << found->second.candidate->cost << std::endl;
1730 )
1731
1732 found->second = PruneStruct{ newCand };
1733 } else if ( newCand->cost == found->second.candidate->cost ) {
1734 // if one of the candidates contains a deleted identifier, can pick the other,
1735 // since deleted expressions should not be ambiguous if there is another option
1736 // that is at least as good
1737 if ( findDeletedExpr( newCand->expr ) ) {
1738 // do nothing
1739 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1740 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1741 PRINT( std::cerr << "current is deleted" << std::endl; )
1742 found->second = PruneStruct{ newCand };
1743 } else {
1744 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1745 found->second.ambiguous = true;
1746 }
1747 } else {
1748 // xxx - can satisfyAssertions increase the cost?
1749 PRINT(
1750 std::cerr << "cost " << newCand->cost << " loses to "
1751 << found->second.candidate->cost << std::endl;
1752 )
1753 }
1754 } else {
1755 selected.emplace_hint( found, mangleName, newCand );
1756 }
1757 }
1758 }
1759
1760 // report unambiguous min-cost candidates
1761 // CandidateList out;
1762 for ( auto & target : selected ) {
1763 if ( target.second.ambiguous ) continue;
1764
1765 CandidateRef cand = target.second.candidate;
1766
1767 ast::ptr< ast::Type > newResult = cand->expr->result;
1768 cand->env.applyFree( newResult );
1769 cand->expr = ast::mutate_field(
1770 cand->expr.get(), &ast::Expr::result, std::move( newResult ) );
1771
1772 out.emplace_back( cand );
1773 }
1774 // if everything is lost in satisfyAssertions, report the error
1775 return !selected.empty();
1776}
1777
1778void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
1779 // Find alternatives for expression
1780 ast::Pass<Finder> finder{ *this };
1781 expr->accept( finder );
1782
1783 if ( mode.failFast && candidates.empty() ) {
1784 switch(finder.core.reason.code) {
1785 case Finder::NotFound:
1786 { SemanticError( expr, "No alternatives for expression " ); break; }
1787 case Finder::NoMatch:
1788 { SemanticError( expr, "Invalid application of existing declaration(s) in expression " ); break; }
1789 case Finder::ArgsToFew:
1790 case Finder::ArgsToMany:
1791 case Finder::RetsToFew:
1792 case Finder::RetsToMany:
1793 case Finder::NoReason:
1794 default:
1795 { SemanticError( expr->location, "No reasonable alternatives for expression : reasons unkown" ); }
1796 }
1797 }
1798
1799 /*
1800 if ( mode.satisfyAssns || mode.prune ) {
1801 // trim candidates to just those where the assertions are satisfiable
1802 // - necessary pre-requisite to pruning
1803 CandidateList satisfied;
1804 std::vector< std::string > errors;
1805 for ( CandidateRef & candidate : candidates ) {
1806 satisfyAssertions( candidate, localSyms, satisfied, errors );
1807 }
1808
1809 // fail early if none such
1810 if ( mode.failFast && satisfied.empty() ) {
1811 std::ostringstream stream;
1812 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1813 for ( const auto& err : errors ) {
1814 stream << err;
1815 }
1816 SemanticError( expr->location, stream.str() );
1817 }
1818
1819 // reset candidates
1820 candidates = move( satisfied );
1821 }
1822 */
1823
1824 if ( mode.prune ) {
1825 // trim candidates to single best one
1826 PRINT(
1827 std::cerr << "alternatives before prune:" << std::endl;
1828 print( std::cerr, candidates );
1829 )
1830
1831 CandidateList pruned;
1832 std::vector<std::string> errors;
1833 bool found = pruneCandidates( candidates, pruned, errors );
1834
1835 if ( mode.failFast && pruned.empty() ) {
1836 std::ostringstream stream;
1837 if (found) {
1838 CandidateList winners = findMinCost( candidates );
1839 stream << "Cannot choose between " << winners.size() << " alternatives for "
1840 "expression\n";
1841 ast::print( stream, expr );
1842 stream << " Alternatives are:\n";
1843 print( stream, winners, 1 );
1844 SemanticError( expr->location, stream.str() );
1845 }
1846 else {
1847 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1848 for ( const auto& err : errors ) {
1849 stream << err;
1850 }
1851 SemanticError( expr->location, stream.str() );
1852 }
1853 }
1854
1855 auto oldsize = candidates.size();
1856 candidates = std::move( pruned );
1857
1858 PRINT(
1859 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1860 )
1861 PRINT(
1862 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1863 << std::endl;
1864 )
1865 }
1866
1867 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1868 // adjusted
1869 if ( mode.adjust ) {
1870 for ( CandidateRef & r : candidates ) {
1871 r->expr = ast::mutate_field(
1872 r->expr.get(), &ast::Expr::result,
1873 adjustExprType( r->expr->result, r->env, context.symtab ) );
1874 }
1875 }
1876
1877 // Central location to handle gcc extension keyword, etc. for all expressions
1878 for ( CandidateRef & r : candidates ) {
1879 if ( r->expr->extension != expr->extension ) {
1880 r->expr.get_and_mutate()->extension = expr->extension;
1881 }
1882 }
1883}
1884
1885std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1886 const std::vector< ast::ptr< ast::Expr > > & xs
1887) {
1888 std::vector< CandidateFinder > out;
1889
1890 for ( const auto & x : xs ) {
1891 out.emplace_back( context, env );
1892 out.back().find( x, ResolvMode::withAdjustment() );
1893
1894 PRINT(
1895 std::cerr << "findSubExprs" << std::endl;
1896 print( std::cerr, out.back().candidates );
1897 )
1898 }
1899
1900 return out;
1901}
1902
1903} // namespace ResolvExpr
1904
1905// Local Variables: //
1906// tab-width: 4 //
1907// mode: c++ //
1908// compile-command: "make install" //
1909// End: //
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