source: src/ResolvExpr/CandidateFinder.cpp@ 3e5dd913

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 3e5dd913 was 3e5dd913, checked in by Fangren Yu <f37yu@…>, 5 years ago

reimplement function type and eliminate deep copy
  • Property mode set to 100644
File size: 67.7 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 : Tue Oct 1 14:55:00 2019
13// Update Count : 2
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 "SymTab/Validate.h" // for validateType
44#include "Tuples/Tuples.h" // for handleTupleAssignment
45#include "InitTweak/InitTweak.h" // for getPointerBase
46
47#include "Common/Stats/Counter.h"
48
49#define PRINT( text ) if ( resolvep ) { text }
50
51namespace ResolvExpr {
52
53const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
54 if ( expr->result.as< ast::ReferenceType >() ) {
55 // cast away reference from expr
56 cost.incReference();
57 return new ast::CastExpr{ expr, expr->result->stripReferences() };
58 }
59
60 return expr;
61}
62
63/// Unique identifier for matching expression resolutions to their requesting expression
64UniqueId globalResnSlot = 0;
65
66Cost computeConversionCost(
67 const ast::Type * argType, const ast::Type * paramType, bool argIsLvalue,
68 const ast::SymbolTable & symtab, const ast::TypeEnvironment & env
69) {
70 PRINT(
71 std::cerr << std::endl << "converting ";
72 ast::print( std::cerr, argType, 2 );
73 std::cerr << std::endl << " to ";
74 ast::print( std::cerr, paramType, 2 );
75 std::cerr << std::endl << "environment is: ";
76 ast::print( std::cerr, env, 2 );
77 std::cerr << std::endl;
78 )
79 Cost convCost = conversionCost( argType, paramType, argIsLvalue, symtab, env );
80 PRINT(
81 std::cerr << std::endl << "cost is " << convCost << std::endl;
82 )
83 if ( convCost == Cost::infinity ) return convCost;
84 convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
85 PRINT(
86 std::cerr << "cost with polycost is " << convCost << std::endl;
87 )
88 return convCost;
89}
90
91namespace {
92 /// First index is which argument, second is which alternative, third is which exploded element
93 using ExplodedArgs_new = std::deque< std::vector< ExplodedArg > >;
94
95 /// Returns a list of alternatives with the minimum cost in the given list
96 CandidateList findMinCost( const CandidateList & candidates ) {
97 CandidateList out;
98 Cost minCost = Cost::infinity;
99 for ( const CandidateRef & r : candidates ) {
100 if ( r->cost < minCost ) {
101 minCost = r->cost;
102 out.clear();
103 out.emplace_back( r );
104 } else if ( r->cost == minCost ) {
105 out.emplace_back( r );
106 }
107 }
108 return out;
109 }
110
111 /// Computes conversion cost for a given expression to a given type
112 const ast::Expr * computeExpressionConversionCost(
113 const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost
114 ) {
115 Cost convCost = computeConversionCost(
116 arg->result, paramType, arg->get_lvalue(), symtab, env );
117 outCost += convCost;
118
119 // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires
120 // conversion. Ignore poly cost for now, since this requires resolution of the cast to
121 // infer parameters and this does not currently work for the reason stated below
122 Cost tmpCost = convCost;
123 tmpCost.incPoly( -tmpCost.get_polyCost() );
124 if ( tmpCost != Cost::zero ) {
125 ast::ptr< ast::Type > newType = paramType;
126 env.apply( newType );
127 return new ast::CastExpr{ arg, newType };
128
129 // xxx - *should* be able to resolve this cast, but at the moment pointers are not
130 // castable to zero_t, but are implicitly convertible. This is clearly inconsistent,
131 // once this is fixed it should be possible to resolve the cast.
132 // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable,
133 // but it shouldn't be because this makes the conversion from DT* to DT* since
134 // commontype(zero_t, DT*) is DT*, rather than nothing
135
136 // CandidateFinder finder{ symtab, env };
137 // finder.find( arg, ResolvMode::withAdjustment() );
138 // assertf( finder.candidates.size() > 0,
139 // "Somehow castable expression failed to find alternatives." );
140 // assertf( finder.candidates.size() == 1,
141 // "Somehow got multiple alternatives for known cast expression." );
142 // return finder.candidates.front()->expr;
143 }
144
145 return arg;
146 }
147
148 /// Computes conversion cost for a given candidate
149 Cost computeApplicationConversionCost(
150 CandidateRef cand, const ast::SymbolTable & symtab
151 ) {
152 auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
153 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
154 auto function = pointer->base.strict_as< ast::FunctionType >();
155
156 Cost convCost = Cost::zero;
157 const auto & params = function->params;
158 auto param = params.begin();
159 auto & args = appExpr->args;
160
161 for ( unsigned i = 0; i < args.size(); ++i ) {
162 const ast::Type * argType = args[i]->result;
163 PRINT(
164 std::cerr << "arg expression:" << std::endl;
165 ast::print( std::cerr, args[i], 2 );
166 std::cerr << "--- results are" << std::endl;
167 ast::print( std::cerr, argType, 2 );
168 )
169
170 if ( param == params.end() ) {
171 if ( function->isVarArgs ) {
172 convCost.incUnsafe();
173 PRINT( std::cerr << "end of params with varargs function: inc unsafe: "
174 << convCost << std::endl; ; )
175 // convert reference-typed expressions into value-typed expressions
176 cand->expr = ast::mutate_field_index(
177 appExpr, &ast::ApplicationExpr::args, i,
178 referenceToRvalueConversion( args[i], convCost ) );
179 continue;
180 } else return Cost::infinity;
181 }
182
183 if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
184 // Default arguments should be free - don't include conversion cost.
185 // Unwrap them here because they are not relevant to the rest of the system
186 cand->expr = ast::mutate_field_index(
187 appExpr, &ast::ApplicationExpr::args, i, def->expr );
188 ++param;
189 continue;
190 }
191
192 // mark conversion cost and also specialization cost of param type
193 // const ast::Type * paramType = (*param)->get_type();
194 cand->expr = ast::mutate_field_index(
195 appExpr, &ast::ApplicationExpr::args, i,
196 computeExpressionConversionCost(
197 args[i], *param, symtab, cand->env, convCost ) );
198 convCost.decSpec( specCost( *param ) );
199 ++param; // can't be in for-loop update because of the continue
200 }
201
202 if ( param != params.end() ) return Cost::infinity;
203
204 // specialization cost of return types can't be accounted for directly, it disables
205 // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
206 //
207 // forall(otype OS) {
208 // void ?|?(OS&, int); // with newline
209 // OS& ?|?(OS&, int); // no newline, always chosen due to more specialization
210 // }
211
212 // mark type variable and specialization cost of forall clause
213 convCost.incVar( function->forall.size() );
214 convCost.decSpec( function->assertions.size() );
215
216 return convCost;
217 }
218
219 void makeUnifiableVars(
220 const ast::FunctionType * type, ast::OpenVarSet & unifiableVars,
221 ast::AssertionSet & need
222 ) {
223 for ( auto & tyvar : type->forall ) {
224 unifiableVars[ *tyvar ] = ast::TypeDecl::Data{ tyvar->base };
225 }
226 for ( auto & assn : type->assertions ) {
227 need[ assn ].isUsed = true;
228 }
229 }
230
231 /// Gets a default value from an initializer, nullptr if not present
232 const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
233 if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
234 if ( auto ce = si->value.as< ast::CastExpr >() ) {
235 return ce->arg.as< ast::ConstantExpr >();
236 } else {
237 return si->value.as< ast::ConstantExpr >();
238 }
239 }
240 return nullptr;
241 }
242
243 /// State to iteratively build a match of parameter expressions to arguments
244 struct ArgPack {
245 std::size_t parent; ///< Index of parent pack
246 ast::ptr< ast::Expr > expr; ///< The argument stored here
247 Cost cost; ///< The cost of this argument
248 ast::TypeEnvironment env; ///< Environment for this pack
249 ast::AssertionSet need; ///< Assertions outstanding for this pack
250 ast::AssertionSet have; ///< Assertions found for this pack
251 ast::OpenVarSet open; ///< Open variables for this pack
252 unsigned nextArg; ///< Index of next argument in arguments list
253 unsigned tupleStart; ///< Number of tuples that start at this index
254 unsigned nextExpl; ///< Index of next exploded element
255 unsigned explAlt; ///< Index of alternative for nextExpl > 0
256
257 ArgPack()
258 : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ),
259 tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
260
261 ArgPack(
262 const ast::TypeEnvironment & env, const ast::AssertionSet & need,
263 const ast::AssertionSet & have, const ast::OpenVarSet & open )
264 : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ),
265 open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
266
267 ArgPack(
268 std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env,
269 ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open,
270 unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero,
271 unsigned nextExpl = 0, unsigned explAlt = 0 )
272 : parent(parent), expr( expr ), cost( cost ), env( move( env ) ), need( move( need ) ),
273 have( move( have ) ), open( move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
274 nextExpl( nextExpl ), explAlt( explAlt ) {}
275
276 ArgPack(
277 const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need,
278 ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
279 : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( move( env ) ),
280 need( move( need ) ), have( move( have ) ), open( move( open ) ), nextArg( nextArg ),
281 tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
282
283 /// true if this pack is in the middle of an exploded argument
284 bool hasExpl() const { return nextExpl > 0; }
285
286 /// Gets the list of exploded candidates for this pack
287 const ExplodedArg & getExpl( const ExplodedArgs_new & args ) const {
288 return args[ nextArg-1 ][ explAlt ];
289 }
290
291 /// Ends a tuple expression, consolidating the appropriate args
292 void endTuple( const std::vector< ArgPack > & packs ) {
293 // add all expressions in tuple to list, summing cost
294 std::deque< const ast::Expr * > exprs;
295 const ArgPack * pack = this;
296 if ( expr ) { exprs.emplace_front( expr ); }
297 while ( pack->tupleStart == 0 ) {
298 pack = &packs[pack->parent];
299 exprs.emplace_front( pack->expr );
300 cost += pack->cost;
301 }
302 // reset pack to appropriate tuple
303 std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
304 expr = new ast::TupleExpr{ expr->location, move( exprv ) };
305 tupleStart = pack->tupleStart - 1;
306 parent = pack->parent;
307 }
308 };
309
310 /// Instantiates an argument to match a parameter, returns false if no matching results left
311 bool instantiateArgument(
312 const ast::Type * paramType, const ast::Init * init, const ExplodedArgs_new & args,
313 std::vector< ArgPack > & results, std::size_t & genStart, const ast::SymbolTable & symtab,
314 unsigned nTuples = 0
315 ) {
316 if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
317 // paramType is a TupleType -- group args into a TupleExpr
318 ++nTuples;
319 for ( const ast::Type * type : *tupleType ) {
320 // xxx - dropping initializer changes behaviour from previous, but seems correct
321 // ^^^ need to handle the case where a tuple has a default argument
322 if ( ! instantiateArgument(
323 type, nullptr, args, results, genStart, symtab, nTuples ) ) return false;
324 nTuples = 0;
325 }
326 // re-constitute tuples for final generation
327 for ( auto i = genStart; i < results.size(); ++i ) {
328 results[i].endTuple( results );
329 }
330 return true;
331 } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
332 // paramType is a ttype, consumes all remaining arguments
333
334 // completed tuples; will be spliced to end of results to finish
335 std::vector< ArgPack > finalResults{};
336
337 // iterate until all results completed
338 std::size_t genEnd;
339 ++nTuples;
340 do {
341 genEnd = results.size();
342
343 // add another argument to results
344 for ( std::size_t i = genStart; i < genEnd; ++i ) {
345 unsigned nextArg = results[i].nextArg;
346
347 // use next element of exploded tuple if present
348 if ( results[i].hasExpl() ) {
349 const ExplodedArg & expl = results[i].getExpl( args );
350
351 unsigned nextExpl = results[i].nextExpl + 1;
352 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
353
354 results.emplace_back(
355 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
356 copy( results[i].need ), copy( results[i].have ),
357 copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
358 results[i].explAlt );
359
360 continue;
361 }
362
363 // finish result when out of arguments
364 if ( nextArg >= args.size() ) {
365 ArgPack newResult{
366 results[i].env, results[i].need, results[i].have, results[i].open };
367 newResult.nextArg = nextArg;
368 const ast::Type * argType = nullptr;
369
370 if ( nTuples > 0 || ! results[i].expr ) {
371 // first iteration or no expression to clone,
372 // push empty tuple expression
373 newResult.parent = i;
374 newResult.expr = new ast::TupleExpr{ CodeLocation{}, {} };
375 argType = newResult.expr->result;
376 } else {
377 // clone result to collect tuple
378 newResult.parent = results[i].parent;
379 newResult.cost = results[i].cost;
380 newResult.tupleStart = results[i].tupleStart;
381 newResult.expr = results[i].expr;
382 argType = newResult.expr->result;
383
384 if ( results[i].tupleStart > 0 && Tuples::isTtype( argType ) ) {
385 // the case where a ttype value is passed directly is special,
386 // e.g. for argument forwarding purposes
387 // xxx - what if passing multiple arguments, last of which is
388 // ttype?
389 // xxx - what would happen if unify was changed so that unifying
390 // tuple
391 // types flattened both before unifying lists? then pass in
392 // TupleType (ttype) below.
393 --newResult.tupleStart;
394 } else {
395 // collapse leftover arguments into tuple
396 newResult.endTuple( results );
397 argType = newResult.expr->result;
398 }
399 }
400
401 // check unification for ttype before adding to final
402 if (
403 unify(
404 ttype, argType, newResult.env, newResult.need, newResult.have,
405 newResult.open, symtab )
406 ) {
407 finalResults.emplace_back( move( newResult ) );
408 }
409
410 continue;
411 }
412
413 // add each possible next argument
414 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
415 const ExplodedArg & expl = args[nextArg][j];
416
417 // fresh copies of parent parameters for this iteration
418 ast::TypeEnvironment env = results[i].env;
419 ast::OpenVarSet open = results[i].open;
420
421 env.addActual( expl.env, open );
422
423 // skip empty tuple arguments by (nearly) cloning parent into next gen
424 if ( expl.exprs.empty() ) {
425 results.emplace_back(
426 results[i], move( env ), copy( results[i].need ),
427 copy( results[i].have ), move( open ), nextArg + 1, expl.cost );
428
429 continue;
430 }
431
432 // add new result
433 results.emplace_back(
434 i, expl.exprs.front(), move( env ), copy( results[i].need ),
435 copy( results[i].have ), move( open ), nextArg + 1, nTuples,
436 expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
437 }
438 }
439
440 // reset for next round
441 genStart = genEnd;
442 nTuples = 0;
443 } while ( genEnd != results.size() );
444
445 // splice final results onto results
446 for ( std::size_t i = 0; i < finalResults.size(); ++i ) {
447 results.emplace_back( move( finalResults[i] ) );
448 }
449 return ! finalResults.empty();
450 }
451
452 // iterate each current subresult
453 std::size_t genEnd = results.size();
454 for ( std::size_t i = genStart; i < genEnd; ++i ) {
455 unsigned nextArg = results[i].nextArg;
456
457 // use remainder of exploded tuple if present
458 if ( results[i].hasExpl() ) {
459 const ExplodedArg & expl = results[i].getExpl( args );
460 const ast::Expr * expr = expl.exprs[ results[i].nextExpl ];
461
462 ast::TypeEnvironment env = results[i].env;
463 ast::AssertionSet need = results[i].need, have = results[i].have;
464 ast::OpenVarSet open = results[i].open;
465
466 const ast::Type * argType = expr->result;
467
468 PRINT(
469 std::cerr << "param type is ";
470 ast::print( std::cerr, paramType );
471 std::cerr << std::endl << "arg type is ";
472 ast::print( std::cerr, argType );
473 std::cerr << std::endl;
474 )
475
476 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
477 unsigned nextExpl = results[i].nextExpl + 1;
478 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
479
480 results.emplace_back(
481 i, expr, move( env ), move( need ), move( have ), move( open ), nextArg,
482 nTuples, Cost::zero, nextExpl, results[i].explAlt );
483 }
484
485 continue;
486 }
487
488 // use default initializers if out of arguments
489 if ( nextArg >= args.size() ) {
490 if ( const ast::ConstantExpr * cnst = getDefaultValue( init ) ) {
491 ast::TypeEnvironment env = results[i].env;
492 ast::AssertionSet need = results[i].need, have = results[i].have;
493 ast::OpenVarSet open = results[i].open;
494
495 if ( unify( paramType, cnst->result, env, need, have, open, symtab ) ) {
496 results.emplace_back(
497 i, new ast::DefaultArgExpr{ cnst->location, cnst }, move( env ),
498 move( need ), move( have ), move( open ), nextArg, nTuples );
499 }
500 }
501
502 continue;
503 }
504
505 // Check each possible next argument
506 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
507 const ExplodedArg & expl = args[nextArg][j];
508
509 // fresh copies of parent parameters for this iteration
510 ast::TypeEnvironment env = results[i].env;
511 ast::AssertionSet need = results[i].need, have = results[i].have;
512 ast::OpenVarSet open = results[i].open;
513
514 env.addActual( expl.env, open );
515
516 // skip empty tuple arguments by (nearly) cloning parent into next gen
517 if ( expl.exprs.empty() ) {
518 results.emplace_back(
519 results[i], move( env ), move( need ), move( have ), move( open ),
520 nextArg + 1, expl.cost );
521
522 continue;
523 }
524
525 // consider only first exploded arg
526 const ast::Expr * expr = expl.exprs.front();
527 const ast::Type * argType = expr->result;
528
529 PRINT(
530 std::cerr << "param type is ";
531 ast::print( std::cerr, paramType );
532 std::cerr << std::endl << "arg type is ";
533 ast::print( std::cerr, argType );
534 std::cerr << std::endl;
535 )
536
537 // attempt to unify types
538 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
539 // add new result
540 results.emplace_back(
541 i, expr, move( env ), move( need ), move( have ), move( open ),
542 nextArg + 1, nTuples, expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
543 }
544 }
545 }
546
547 // reset for next parameter
548 genStart = genEnd;
549
550 return genEnd != results.size(); // were any new results added?
551 }
552
553 /// Generate a cast expression from `arg` to `toType`
554 const ast::Expr * restructureCast(
555 ast::ptr< ast::Expr > & arg, const ast::Type * toType, ast::GeneratedFlag isGenerated = ast::GeneratedCast
556 ) {
557 if (
558 arg->result->size() > 1
559 && ! toType->isVoid()
560 && ! dynamic_cast< const ast::ReferenceType * >( toType )
561 ) {
562 // Argument is a tuple and the target type is neither void nor a reference. Cast each
563 // member of the tuple to its corresponding target type, producing the tuple of those
564 // cast expressions. If there are more components of the tuple than components in the
565 // target type, then excess components do not come out in the result expression (but
566 // UniqueExpr ensures that the side effects will still be produced)
567 if ( Tuples::maybeImpureIgnoreUnique( arg ) ) {
568 // expressions which may contain side effects require a single unique instance of
569 // the expression
570 arg = new ast::UniqueExpr{ arg->location, arg };
571 }
572 std::vector< ast::ptr< ast::Expr > > components;
573 for ( unsigned i = 0; i < toType->size(); ++i ) {
574 // cast each component
575 ast::ptr< ast::Expr > idx = new ast::TupleIndexExpr{ arg->location, arg, i };
576 components.emplace_back(
577 restructureCast( idx, toType->getComponent( i ), isGenerated ) );
578 }
579 return new ast::TupleExpr{ arg->location, move( components ) };
580 } else {
581 // handle normally
582 return new ast::CastExpr{ arg->location, arg, toType, isGenerated };
583 }
584 }
585
586 /// Gets the name from an untyped member expression (must be NameExpr)
587 const std::string & getMemberName( const ast::UntypedMemberExpr * memberExpr ) {
588 if ( memberExpr->member.as< ast::ConstantExpr >() ) {
589 SemanticError( memberExpr, "Indexed access to struct fields unsupported: " );
590 }
591
592 return memberExpr->member.strict_as< ast::NameExpr >()->name;
593 }
594
595 /// Actually visits expressions to find their candidate interpretations
596 class Finder final : public ast::WithShortCircuiting {
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 : symtab( f.localSyms ), selfFinder( f ), candidates( f.candidates ), tenv( f.env ),
621 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 = 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], move( env ), copy( results[i].need ),
786 copy( results[i].have ), 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(), move( env ), copy( results[i].need ),
795 copy( results[i].have ), 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( 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{ symtab, 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 funcFinder.otypeKeys.insert(Mangle::mangle(argType, Mangle::NoGenericParams | Mangle::Type));
901 }
902 }
903 }
904 // if candidates are already produced, do not fail
905 // xxx - is it possible that handleTupleAssignment and main finder both produce candidates?
906 // this means there exists ctor/assign functions with a tuple as first parameter.
907 funcFinder.find( untypedExpr->func, selfFinder.candidates.empty() ? ResolvMode::withAdjustment() : ResolvMode::withoutFailFast() );
908 // short-circuit if no candidates
909 // if ( funcFinder.candidates.empty() ) return;
910
911 reason.code = NoMatch;
912
913 // find function operators
914 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" };
915 CandidateFinder opFinder{ symtab, tenv };
916 // okay if there aren't any function operations
917 opFinder.find( opExpr, ResolvMode::withoutFailFast() );
918 PRINT(
919 std::cerr << "known function ops:" << std::endl;
920 print( std::cerr, opFinder.candidates, 1 );
921 )
922
923 // pre-explode arguments
924 ExplodedArgs_new argExpansions;
925 for ( const CandidateFinder & args : argCandidates ) {
926 argExpansions.emplace_back();
927 auto & argE = argExpansions.back();
928 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
929 }
930
931 // Find function matches
932 CandidateList found;
933 SemanticErrorException errors;
934 for ( CandidateRef & func : funcFinder ) {
935 try {
936 PRINT(
937 std::cerr << "working on alternative:" << std::endl;
938 print( std::cerr, *func, 2 );
939 )
940
941 // check if the type is a pointer to function
942 const ast::Type * funcResult = func->expr->result->stripReferences();
943 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
944 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
945 CandidateRef newFunc{ new Candidate{ *func } };
946 newFunc->expr =
947 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
948 makeFunctionCandidates( newFunc, function, argExpansions, found );
949 }
950 } else if (
951 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
952 ) {
953 if ( const ast::EqvClass * clz = func->env.lookup( *inst ) ) {
954 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
955 CandidateRef newFunc{ new Candidate{ *func } };
956 newFunc->expr =
957 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
958 makeFunctionCandidates( newFunc, function, argExpansions, found );
959 }
960 }
961 }
962 } catch ( SemanticErrorException & e ) { errors.append( e ); }
963 }
964
965 // Find matches on function operators `?()`
966 if ( ! opFinder.candidates.empty() ) {
967 // add exploded function alternatives to front of argument list
968 std::vector< ExplodedArg > funcE;
969 funcE.reserve( funcFinder.candidates.size() );
970 for ( const CandidateRef & func : funcFinder ) {
971 funcE.emplace_back( *func, symtab );
972 }
973 argExpansions.emplace_front( move( funcE ) );
974
975 for ( const CandidateRef & op : opFinder ) {
976 try {
977 // check if type is pointer-to-function
978 const ast::Type * opResult = op->expr->result->stripReferences();
979 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
980 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
981 CandidateRef newOp{ new Candidate{ *op} };
982 newOp->expr =
983 referenceToRvalueConversion( newOp->expr, newOp->cost );
984 makeFunctionCandidates( newOp, function, argExpansions, found );
985 }
986 }
987 } catch ( SemanticErrorException & e ) { errors.append( e ); }
988 }
989 }
990
991 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
992 // candidates
993 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
994
995 // Compute conversion costs
996 for ( CandidateRef & withFunc : found ) {
997 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
998
999 PRINT(
1000 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
1001 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
1002 auto function = pointer->base.strict_as< ast::FunctionType >();
1003
1004 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
1005 std::cerr << "parameters are:" << std::endl;
1006 ast::printAll( std::cerr, function->params, 2 );
1007 std::cerr << "arguments are:" << std::endl;
1008 ast::printAll( std::cerr, appExpr->args, 2 );
1009 std::cerr << "bindings are:" << std::endl;
1010 ast::print( std::cerr, withFunc->env, 2 );
1011 std::cerr << "cost is: " << withFunc->cost << std::endl;
1012 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
1013 )
1014
1015 if ( cvtCost != Cost::infinity ) {
1016 withFunc->cvtCost = cvtCost;
1017 candidates.emplace_back( move( withFunc ) );
1018 }
1019 }
1020 found = move( candidates );
1021
1022 // use a new list so that candidates are not examined by addAnonConversions twice
1023 CandidateList winners = findMinCost( found );
1024 promoteCvtCost( winners );
1025
1026 // function may return a struct/union value, in which case we need to add candidates
1027 // for implicit conversions to each of the anonymous members, which must happen after
1028 // `findMinCost`, since anon conversions are never the cheapest
1029 for ( const CandidateRef & c : winners ) {
1030 addAnonConversions( c );
1031 }
1032 spliceBegin( candidates, winners );
1033
1034 if ( candidates.empty() && targetType && ! targetType->isVoid() ) {
1035 // If resolution is unsuccessful with a target type, try again without, since it
1036 // will sometimes succeed when it wouldn't with a target type binding.
1037 // For example:
1038 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
1039 // const char * x = "hello world";
1040 // unsigned char ch = x[0];
1041 // Fails with simple return type binding (xxx -- check this!) as follows:
1042 // * T is bound to unsigned char
1043 // * (x: const char *) is unified with unsigned char *, which fails
1044 // xxx -- fix this better
1045 targetType = nullptr;
1046 postvisit( untypedExpr );
1047 }
1048 }
1049
1050 /// true if expression is an lvalue
1051 static bool isLvalue( const ast::Expr * x ) {
1052 return x->result && ( x->get_lvalue() || x->result.as< ast::ReferenceType >() );
1053 }
1054
1055 void postvisit( const ast::AddressExpr * addressExpr ) {
1056 CandidateFinder finder{ symtab, tenv };
1057 finder.find( addressExpr->arg );
1058
1059 if( finder.candidates.empty() ) return;
1060
1061 reason.code = NoMatch;
1062
1063 for ( CandidateRef & r : finder.candidates ) {
1064 if ( ! isLvalue( r->expr ) ) continue;
1065 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
1066 }
1067 }
1068
1069 void postvisit( const ast::LabelAddressExpr * labelExpr ) {
1070 addCandidate( labelExpr, tenv );
1071 }
1072
1073 void postvisit( const ast::CastExpr * castExpr ) {
1074 ast::ptr< ast::Type > toType = castExpr->result;
1075 assert( toType );
1076 toType = resolveTypeof( toType, symtab );
1077 // toType = SymTab::validateType( castExpr->location, toType, symtab );
1078 toType = adjustExprType( toType, tenv, symtab );
1079
1080 CandidateFinder finder{ symtab, tenv, toType };
1081 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1082
1083 if( !finder.candidates.empty() ) reason.code = NoMatch;
1084
1085 CandidateList matches;
1086 for ( CandidateRef & cand : finder.candidates ) {
1087 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1088 ast::OpenVarSet open( cand->open );
1089
1090 cand->env.extractOpenVars( open );
1091
1092 // It is possible that a cast can throw away some values in a multiply-valued
1093 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1094 // subexpression results that are cast directly. The candidate is invalid if it
1095 // has fewer results than there are types to cast to.
1096 int discardedValues = cand->expr->result->size() - toType->size();
1097 if ( discardedValues < 0 ) continue;
1098
1099 // unification run for side-effects
1100 unify( toType, cand->expr->result, cand->env, need, have, open, symtab );
1101 Cost thisCost =
1102 (castExpr->isGenerated == ast::GeneratedFlag::GeneratedCast)
1103 ? conversionCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env )
1104 : castCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env );
1105
1106 PRINT(
1107 std::cerr << "working on cast with result: " << toType << std::endl;
1108 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1109 std::cerr << "env: " << cand->env << std::endl;
1110 )
1111 if ( thisCost != Cost::infinity ) {
1112 PRINT(
1113 std::cerr << "has finite cost." << std::endl;
1114 )
1115 // count one safe conversion for each value that is thrown away
1116 thisCost.incSafe( discardedValues );
1117 CandidateRef newCand = std::make_shared<Candidate>(
1118 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1119 copy( cand->env ), move( open ), move( need ), cand->cost,
1120 cand->cost + thisCost );
1121 inferParameters( newCand, matches );
1122 }
1123 }
1124
1125 // select first on argument cost, then conversion cost
1126 CandidateList minArgCost = findMinCost( matches );
1127 promoteCvtCost( minArgCost );
1128 candidates = findMinCost( minArgCost );
1129 }
1130
1131 void postvisit( const ast::VirtualCastExpr * castExpr ) {
1132 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1133 CandidateFinder finder{ symtab, tenv };
1134 // don't prune here, all alternatives guaranteed to have same type
1135 finder.find( castExpr->arg, ResolvMode::withoutPrune() );
1136 for ( CandidateRef & r : finder.candidates ) {
1137 addCandidate(
1138 *r,
1139 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
1140 }
1141 }
1142
1143 void postvisit( const ast::KeywordCastExpr * castExpr ) {
1144 const auto & loc = castExpr->location;
1145 assertf( castExpr->result, "Cast target should have been set in Validate." );
1146 auto ref = castExpr->result.strict_as<ast::ReferenceType>();
1147 auto inst = ref->base.strict_as<ast::StructInstType>();
1148 auto target = inst->base.get();
1149
1150 CandidateFinder finder{ symtab, tenv };
1151
1152 auto pick_alternatives = [target, this](CandidateList & found, bool expect_ref) {
1153 for(auto & cand : found) {
1154 const ast::Type * expr = cand->expr->result.get();
1155 if(expect_ref) {
1156 auto res = dynamic_cast<const ast::ReferenceType*>(expr);
1157 if(!res) { continue; }
1158 expr = res->base.get();
1159 }
1160
1161 if(auto insttype = dynamic_cast<const ast::TypeInstType*>(expr)) {
1162 auto td = cand->env.lookup(*insttype);
1163 if(!td) { continue; }
1164 expr = td->bound.get();
1165 }
1166
1167 if(auto base = dynamic_cast<const ast::StructInstType*>(expr)) {
1168 if(base->base == target) {
1169 candidates.push_back( std::move(cand) );
1170 reason.code = NoReason;
1171 }
1172 }
1173 }
1174 };
1175
1176 try {
1177 // Attempt 1 : turn (thread&)X into ($thread&)X.__thrd
1178 // Clone is purely for memory management
1179 std::unique_ptr<const ast::Expr> tech1 { new ast::UntypedMemberExpr(loc, new ast::NameExpr(loc, castExpr->concrete_target.field), castExpr->arg) };
1180
1181 // don't prune here, since it's guaranteed all alternatives will have the same type
1182 finder.find( tech1.get(), ResolvMode::withoutPrune() );
1183 pick_alternatives(finder.candidates, false);
1184
1185 return;
1186 } catch(SemanticErrorException & ) {}
1187
1188 // Fallback : turn (thread&)X into ($thread&)get_thread(X)
1189 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 })) };
1190 // don't prune here, since it's guaranteed all alternatives will have the same type
1191 finder.find( fallback.get(), ResolvMode::withoutPrune() );
1192
1193 pick_alternatives(finder.candidates, true);
1194
1195 // Whatever happens here, we have no more fallbacks
1196 }
1197
1198 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
1199 CandidateFinder aggFinder{ symtab, tenv };
1200 aggFinder.find( memberExpr->aggregate, ResolvMode::withAdjustment() );
1201 for ( CandidateRef & agg : aggFinder.candidates ) {
1202 // it's okay for the aggregate expression to have reference type -- cast it to the
1203 // base type to treat the aggregate as the referenced value
1204 Cost addedCost = Cost::zero;
1205 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1206
1207 // find member of the given type
1208 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1209 addAggMembers(
1210 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1211 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1212 addAggMembers(
1213 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1214 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1215 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1216 }
1217 }
1218 }
1219
1220 void postvisit( const ast::MemberExpr * memberExpr ) {
1221 addCandidate( memberExpr, tenv );
1222 }
1223
1224 void postvisit( const ast::NameExpr * nameExpr ) {
1225 std::vector< ast::SymbolTable::IdData > declList;
1226 if (!selfFinder.otypeKeys.empty()) {
1227 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
1228 assertf(kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS, "special lookup with non-special target: %s", nameExpr->name.c_str());
1229
1230 for (auto & otypeKey: selfFinder.otypeKeys) {
1231 auto result = symtab.specialLookupId(kind, otypeKey);
1232 declList.insert(declList.end(), std::make_move_iterator(result.begin()), std::make_move_iterator(result.end()));
1233 }
1234 }
1235 else {
1236 declList = symtab.lookupId( nameExpr->name );
1237 }
1238 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1239
1240 if( declList.empty() ) return;
1241
1242 reason.code = NoMatch;
1243
1244 for ( auto & data : declList ) {
1245 Cost cost = Cost::zero;
1246 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1247
1248 CandidateRef newCand = std::make_shared<Candidate>(
1249 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, Cost::zero,
1250 cost );
1251 PRINT(
1252 std::cerr << "decl is ";
1253 ast::print( std::cerr, data.id );
1254 std::cerr << std::endl;
1255 std::cerr << "newExpr is ";
1256 ast::print( std::cerr, newExpr );
1257 std::cerr << std::endl;
1258 )
1259 newCand->expr = ast::mutate_field(
1260 newCand->expr.get(), &ast::Expr::result,
1261 renameTyVars( newCand->expr->result ) );
1262 // add anonymous member interpretations whenever an aggregate value type is seen
1263 // as a name expression
1264 addAnonConversions( newCand );
1265 candidates.emplace_back( move( newCand ) );
1266 }
1267 }
1268
1269 void postvisit( const ast::VariableExpr * variableExpr ) {
1270 // not sufficient to just pass `variableExpr` here, type might have changed since
1271 // creation
1272 addCandidate(
1273 new ast::VariableExpr{ variableExpr->location, variableExpr->var }, tenv );
1274 }
1275
1276 void postvisit( const ast::ConstantExpr * constantExpr ) {
1277 addCandidate( constantExpr, tenv );
1278 }
1279
1280 void postvisit( const ast::SizeofExpr * sizeofExpr ) {
1281 if ( sizeofExpr->type ) {
1282 addCandidate(
1283 new ast::SizeofExpr{
1284 sizeofExpr->location, resolveTypeof( sizeofExpr->type, symtab ) },
1285 tenv );
1286 } else {
1287 // find all candidates for the argument to sizeof
1288 CandidateFinder finder{ symtab, tenv };
1289 finder.find( sizeofExpr->expr );
1290 // find the lowest-cost candidate, otherwise ambiguous
1291 CandidateList winners = findMinCost( finder.candidates );
1292 if ( winners.size() != 1 ) {
1293 SemanticError(
1294 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1295 }
1296 // return the lowest-cost candidate
1297 CandidateRef & choice = winners.front();
1298 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1299 choice->cost = Cost::zero;
1300 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1301 }
1302 }
1303
1304 void postvisit( const ast::AlignofExpr * alignofExpr ) {
1305 if ( alignofExpr->type ) {
1306 addCandidate(
1307 new ast::AlignofExpr{
1308 alignofExpr->location, resolveTypeof( alignofExpr->type, symtab ) },
1309 tenv );
1310 } else {
1311 // find all candidates for the argument to alignof
1312 CandidateFinder finder{ symtab, tenv };
1313 finder.find( alignofExpr->expr );
1314 // find the lowest-cost candidate, otherwise ambiguous
1315 CandidateList winners = findMinCost( finder.candidates );
1316 if ( winners.size() != 1 ) {
1317 SemanticError(
1318 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1319 }
1320 // return the lowest-cost candidate
1321 CandidateRef & choice = winners.front();
1322 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1323 choice->cost = Cost::zero;
1324 addCandidate(
1325 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1326 }
1327 }
1328
1329 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
1330 const ast::BaseInstType * aggInst;
1331 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1332 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1333 else return;
1334
1335 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1336 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1337 addCandidate(
1338 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1339 }
1340 }
1341
1342 void postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1343 addCandidate( offsetofExpr, tenv );
1344 }
1345
1346 void postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1347 addCandidate( offsetPackExpr, tenv );
1348 }
1349
1350 void postvisit( const ast::LogicalExpr * logicalExpr ) {
1351 CandidateFinder finder1{ symtab, tenv };
1352 finder1.find( logicalExpr->arg1, ResolvMode::withAdjustment() );
1353 if ( finder1.candidates.empty() ) return;
1354
1355 CandidateFinder finder2{ symtab, tenv };
1356 finder2.find( logicalExpr->arg2, ResolvMode::withAdjustment() );
1357 if ( finder2.candidates.empty() ) return;
1358
1359 reason.code = NoMatch;
1360
1361 for ( const CandidateRef & r1 : finder1.candidates ) {
1362 for ( const CandidateRef & r2 : finder2.candidates ) {
1363 ast::TypeEnvironment env{ r1->env };
1364 env.simpleCombine( r2->env );
1365 ast::OpenVarSet open{ r1->open };
1366 mergeOpenVars( open, r2->open );
1367 ast::AssertionSet need;
1368 mergeAssertionSet( need, r1->need );
1369 mergeAssertionSet( need, r2->need );
1370
1371 addCandidate(
1372 new ast::LogicalExpr{
1373 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
1374 move( env ), move( open ), move( need ), r1->cost + r2->cost );
1375 }
1376 }
1377 }
1378
1379 void postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1380 // candidates for condition
1381 CandidateFinder finder1{ symtab, tenv };
1382 finder1.find( conditionalExpr->arg1, ResolvMode::withAdjustment() );
1383 if ( finder1.candidates.empty() ) return;
1384
1385 // candidates for true result
1386 CandidateFinder finder2{ symtab, tenv };
1387 finder2.find( conditionalExpr->arg2, ResolvMode::withAdjustment() );
1388 if ( finder2.candidates.empty() ) return;
1389
1390 // candidates for false result
1391 CandidateFinder finder3{ symtab, tenv };
1392 finder3.find( conditionalExpr->arg3, ResolvMode::withAdjustment() );
1393 if ( finder3.candidates.empty() ) return;
1394
1395 reason.code = NoMatch;
1396
1397 for ( const CandidateRef & r1 : finder1.candidates ) {
1398 for ( const CandidateRef & r2 : finder2.candidates ) {
1399 for ( const CandidateRef & r3 : finder3.candidates ) {
1400 ast::TypeEnvironment env{ r1->env };
1401 env.simpleCombine( r2->env );
1402 env.simpleCombine( r3->env );
1403 ast::OpenVarSet open{ r1->open };
1404 mergeOpenVars( open, r2->open );
1405 mergeOpenVars( open, r3->open );
1406 ast::AssertionSet need;
1407 mergeAssertionSet( need, r1->need );
1408 mergeAssertionSet( need, r2->need );
1409 mergeAssertionSet( need, r3->need );
1410 ast::AssertionSet have;
1411
1412 // unify true and false results, then infer parameters to produce new
1413 // candidates
1414 ast::ptr< ast::Type > common;
1415 if (
1416 unify(
1417 r2->expr->result, r3->expr->result, env, need, have, open, symtab,
1418 common )
1419 ) {
1420 // generate typed expression
1421 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1422 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1423 newExpr->result = common ? common : r2->expr->result;
1424 // convert both options to result type
1425 Cost cost = r1->cost + r2->cost + r3->cost;
1426 newExpr->arg2 = computeExpressionConversionCost(
1427 newExpr->arg2, newExpr->result, symtab, env, cost );
1428 newExpr->arg3 = computeExpressionConversionCost(
1429 newExpr->arg3, newExpr->result, symtab, env, cost );
1430 // output candidate
1431 CandidateRef newCand = std::make_shared<Candidate>(
1432 newExpr, move( env ), move( open ), move( need ), cost );
1433 inferParameters( newCand, candidates );
1434 }
1435 }
1436 }
1437 }
1438 }
1439
1440 void postvisit( const ast::CommaExpr * commaExpr ) {
1441 ast::TypeEnvironment env{ tenv };
1442 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, symtab, env );
1443
1444 CandidateFinder finder2{ symtab, env };
1445 finder2.find( commaExpr->arg2, ResolvMode::withAdjustment() );
1446
1447 for ( const CandidateRef & r2 : finder2.candidates ) {
1448 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1449 }
1450 }
1451
1452 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1453 addCandidate( ctorExpr, tenv );
1454 }
1455
1456 void postvisit( const ast::ConstructorExpr * ctorExpr ) {
1457 CandidateFinder finder{ symtab, tenv };
1458 finder.find( ctorExpr->callExpr, ResolvMode::withoutPrune() );
1459 for ( CandidateRef & r : finder.candidates ) {
1460 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1461 }
1462 }
1463
1464 void postvisit( const ast::RangeExpr * rangeExpr ) {
1465 // resolve low and high, accept candidates where low and high types unify
1466 CandidateFinder finder1{ symtab, tenv };
1467 finder1.find( rangeExpr->low, ResolvMode::withAdjustment() );
1468 if ( finder1.candidates.empty() ) return;
1469
1470 CandidateFinder finder2{ symtab, tenv };
1471 finder2.find( rangeExpr->high, ResolvMode::withAdjustment() );
1472 if ( finder2.candidates.empty() ) return;
1473
1474 reason.code = NoMatch;
1475
1476 for ( const CandidateRef & r1 : finder1.candidates ) {
1477 for ( const CandidateRef & r2 : finder2.candidates ) {
1478 ast::TypeEnvironment env{ r1->env };
1479 env.simpleCombine( r2->env );
1480 ast::OpenVarSet open{ r1->open };
1481 mergeOpenVars( open, r2->open );
1482 ast::AssertionSet need;
1483 mergeAssertionSet( need, r1->need );
1484 mergeAssertionSet( need, r2->need );
1485 ast::AssertionSet have;
1486
1487 ast::ptr< ast::Type > common;
1488 if (
1489 unify(
1490 r1->expr->result, r2->expr->result, env, need, have, open, symtab,
1491 common )
1492 ) {
1493 // generate new expression
1494 ast::RangeExpr * newExpr =
1495 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1496 newExpr->result = common ? common : r1->expr->result;
1497 // add candidate
1498 CandidateRef newCand = std::make_shared<Candidate>(
1499 newExpr, move( env ), move( open ), move( need ),
1500 r1->cost + r2->cost );
1501 inferParameters( newCand, candidates );
1502 }
1503 }
1504 }
1505 }
1506
1507 void postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1508 std::vector< CandidateFinder > subCandidates =
1509 selfFinder.findSubExprs( tupleExpr->exprs );
1510 std::vector< CandidateList > possibilities;
1511 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1512
1513 for ( const CandidateList & subs : possibilities ) {
1514 std::vector< ast::ptr< ast::Expr > > exprs;
1515 exprs.reserve( subs.size() );
1516 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1517
1518 ast::TypeEnvironment env;
1519 ast::OpenVarSet open;
1520 ast::AssertionSet need;
1521 for ( const CandidateRef & sub : subs ) {
1522 env.simpleCombine( sub->env );
1523 mergeOpenVars( open, sub->open );
1524 mergeAssertionSet( need, sub->need );
1525 }
1526
1527 addCandidate(
1528 new ast::TupleExpr{ tupleExpr->location, move( exprs ) },
1529 move( env ), move( open ), move( need ), sumCost( subs ) );
1530 }
1531 }
1532
1533 void postvisit( const ast::TupleExpr * tupleExpr ) {
1534 addCandidate( tupleExpr, tenv );
1535 }
1536
1537 void postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1538 addCandidate( tupleExpr, tenv );
1539 }
1540
1541 void postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1542 addCandidate( tupleExpr, tenv );
1543 }
1544
1545 void postvisit( const ast::UniqueExpr * unqExpr ) {
1546 CandidateFinder finder{ symtab, tenv };
1547 finder.find( unqExpr->expr, ResolvMode::withAdjustment() );
1548 for ( CandidateRef & r : finder.candidates ) {
1549 // ensure that the the id is passed on so that the expressions are "linked"
1550 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1551 }
1552 }
1553
1554 void postvisit( const ast::StmtExpr * stmtExpr ) {
1555 addCandidate( resolveStmtExpr( stmtExpr, symtab ), tenv );
1556 }
1557
1558 void postvisit( const ast::UntypedInitExpr * initExpr ) {
1559 // handle each option like a cast
1560 CandidateList matches;
1561 PRINT(
1562 std::cerr << "untyped init expr: " << initExpr << std::endl;
1563 )
1564 // O(n^2) checks of d-types with e-types
1565 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1566 // calculate target type
1567 const ast::Type * toType = resolveTypeof( initAlt.type, symtab );
1568 // toType = SymTab::validateType( initExpr->location, toType, symtab );
1569 toType = adjustExprType( toType, tenv, symtab );
1570 // The call to find must occur inside this loop, otherwise polymorphic return
1571 // types are not bound to the initialization type, since return type variables are
1572 // only open for the duration of resolving the UntypedExpr.
1573 CandidateFinder finder{ symtab, tenv, toType };
1574 finder.find( initExpr->expr, ResolvMode::withAdjustment() );
1575 for ( CandidateRef & cand : finder.candidates ) {
1576 if(reason.code == NotFound) reason.code = NoMatch;
1577
1578 ast::TypeEnvironment env{ cand->env };
1579 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1580 ast::OpenVarSet open{ cand->open };
1581
1582 PRINT(
1583 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1584 )
1585
1586 // It is possible that a cast can throw away some values in a multiply-valued
1587 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1588 // the subexpression results that are cast directly. The candidate is invalid
1589 // if it has fewer results than there are types to cast to.
1590 int discardedValues = cand->expr->result->size() - toType->size();
1591 if ( discardedValues < 0 ) continue;
1592
1593 // unification run for side-effects
1594 bool canUnify = unify( toType, cand->expr->result, env, need, have, open, symtab );
1595 (void) canUnify;
1596 Cost thisCost = computeConversionCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1597 symtab, env );
1598 PRINT(
1599 Cost legacyCost = castCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1600 symtab, env );
1601 std::cerr << "Considering initialization:";
1602 std::cerr << std::endl << " FROM: " << cand->expr->result << std::endl;
1603 std::cerr << std::endl << " TO: " << toType << std::endl;
1604 std::cerr << std::endl << " Unification " << (canUnify ? "succeeded" : "failed");
1605 std::cerr << std::endl << " Legacy cost " << legacyCost;
1606 std::cerr << std::endl << " New cost " << thisCost;
1607 std::cerr << std::endl;
1608 )
1609 if ( thisCost != Cost::infinity ) {
1610 // count one safe conversion for each value that is thrown away
1611 thisCost.incSafe( discardedValues );
1612 CandidateRef newCand = std::make_shared<Candidate>(
1613 new ast::InitExpr{
1614 initExpr->location, restructureCast( cand->expr, toType ),
1615 initAlt.designation },
1616 move(env), move( open ), move( need ), cand->cost, thisCost );
1617 inferParameters( newCand, matches );
1618 }
1619 }
1620
1621 }
1622
1623 // select first on argument cost, then conversion cost
1624 CandidateList minArgCost = findMinCost( matches );
1625 promoteCvtCost( minArgCost );
1626 candidates = findMinCost( minArgCost );
1627 }
1628
1629 void postvisit( const ast::InitExpr * ) {
1630 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1631 }
1632
1633 void postvisit( const ast::DeletedExpr * ) {
1634 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1635 }
1636
1637 void postvisit( const ast::GenericExpr * ) {
1638 assertf( false, "_Generic is not yet supported." );
1639 }
1640 };
1641
1642 // size_t Finder::traceId = Stats::Heap::new_stacktrace_id("Finder");
1643 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1644 /// return type. Skips ambiguous candidates.
1645
1646} // anonymous namespace
1647
1648bool CandidateFinder::pruneCandidates( CandidateList & candidates, CandidateList & out, std::vector<std::string> & errors ) {
1649 struct PruneStruct {
1650 CandidateRef candidate;
1651 bool ambiguous;
1652
1653 PruneStruct() = default;
1654 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1655 };
1656
1657 // find lowest-cost candidate for each type
1658 std::unordered_map< std::string, PruneStruct > selected;
1659 // attempt to skip satisfyAssertions on more expensive alternatives if better options have been found
1660 std::sort(candidates.begin(), candidates.end(), [](const CandidateRef & x, const CandidateRef & y){return x->cost < y->cost;});
1661 for ( CandidateRef & candidate : candidates ) {
1662 std::string mangleName;
1663 {
1664 ast::ptr< ast::Type > newType = candidate->expr->result;
1665 assertf(candidate->expr->result, "Result of expression %p for candidate is null", candidate->expr.get());
1666 candidate->env.apply( newType );
1667 mangleName = Mangle::mangle( newType );
1668 }
1669
1670 auto found = selected.find( mangleName );
1671 if (found != selected.end() && found->second.candidate->cost < candidate->cost) {
1672 PRINT(
1673 std::cerr << "cost " << candidate->cost << " loses to "
1674 << found->second.candidate->cost << std::endl;
1675 )
1676 continue;
1677 }
1678
1679 // xxx - when do satisfyAssertions produce more than 1 result?
1680 // this should only happen when initial result type contains
1681 // unbound type parameters, then it should never be pruned by
1682 // the previous step, since renameTyVars guarantees the mangled name
1683 // is unique.
1684 CandidateList satisfied;
1685 bool needRecomputeKey = false;
1686 if (candidate->need.empty()) {
1687 satisfied.emplace_back(candidate);
1688 }
1689 else {
1690 satisfyAssertions(candidate, localSyms, satisfied, errors);
1691 needRecomputeKey = true;
1692 }
1693
1694 for (auto & newCand : satisfied) {
1695 // recomputes type key, if satisfyAssertions changed it
1696 if (needRecomputeKey)
1697 {
1698 ast::ptr< ast::Type > newType = newCand->expr->result;
1699 assertf(newCand->expr->result, "Result of expression %p for candidate is null", newCand->expr.get());
1700 newCand->env.apply( newType );
1701 mangleName = Mangle::mangle( newType );
1702 }
1703 auto found = selected.find( mangleName );
1704 if ( found != selected.end() ) {
1705 if ( newCand->cost < found->second.candidate->cost ) {
1706 PRINT(
1707 std::cerr << "cost " << newCand->cost << " beats "
1708 << found->second.candidate->cost << std::endl;
1709 )
1710
1711 found->second = PruneStruct{ newCand };
1712 } else if ( newCand->cost == found->second.candidate->cost ) {
1713 // if one of the candidates contains a deleted identifier, can pick the other,
1714 // since deleted expressions should not be ambiguous if there is another option
1715 // that is at least as good
1716 if ( findDeletedExpr( newCand->expr ) ) {
1717 // do nothing
1718 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1719 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1720 PRINT( std::cerr << "current is deleted" << std::endl; )
1721 found->second = PruneStruct{ newCand };
1722 } else {
1723 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1724 found->second.ambiguous = true;
1725 }
1726 } else {
1727 // xxx - can satisfyAssertions increase the cost?
1728 PRINT(
1729 std::cerr << "cost " << newCand->cost << " loses to "
1730 << found->second.candidate->cost << std::endl;
1731 )
1732 }
1733 } else {
1734 selected.emplace_hint( found, mangleName, newCand );
1735 }
1736 }
1737 }
1738
1739 // report unambiguous min-cost candidates
1740 // CandidateList out;
1741 for ( auto & target : selected ) {
1742 if ( target.second.ambiguous ) continue;
1743
1744 CandidateRef cand = target.second.candidate;
1745
1746 ast::ptr< ast::Type > newResult = cand->expr->result;
1747 cand->env.applyFree( newResult );
1748 cand->expr = ast::mutate_field(
1749 cand->expr.get(), &ast::Expr::result, move( newResult ) );
1750
1751 out.emplace_back( cand );
1752 }
1753 // if everything is lost in satisfyAssertions, report the error
1754 return !selected.empty();
1755}
1756
1757void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
1758 // Find alternatives for expression
1759 ast::Pass<Finder> finder{ *this };
1760 expr->accept( finder );
1761
1762 if ( mode.failFast && candidates.empty() ) {
1763 switch(finder.core.reason.code) {
1764 case Finder::NotFound:
1765 { SemanticError( expr, "No alternatives for expression " ); break; }
1766 case Finder::NoMatch:
1767 { SemanticError( expr, "Invalid application of existing declaration(s) in expression " ); break; }
1768 case Finder::ArgsToFew:
1769 case Finder::ArgsToMany:
1770 case Finder::RetsToFew:
1771 case Finder::RetsToMany:
1772 case Finder::NoReason:
1773 default:
1774 { SemanticError( expr->location, "No reasonable alternatives for expression : reasons unkown" ); }
1775 }
1776 }
1777
1778 /*
1779 if ( mode.satisfyAssns || mode.prune ) {
1780 // trim candidates to just those where the assertions are satisfiable
1781 // - necessary pre-requisite to pruning
1782 CandidateList satisfied;
1783 std::vector< std::string > errors;
1784 for ( CandidateRef & candidate : candidates ) {
1785 satisfyAssertions( candidate, localSyms, satisfied, errors );
1786 }
1787
1788 // fail early if none such
1789 if ( mode.failFast && satisfied.empty() ) {
1790 std::ostringstream stream;
1791 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1792 for ( const auto& err : errors ) {
1793 stream << err;
1794 }
1795 SemanticError( expr->location, stream.str() );
1796 }
1797
1798 // reset candidates
1799 candidates = move( satisfied );
1800 }
1801 */
1802
1803 if ( mode.prune ) {
1804 // trim candidates to single best one
1805 PRINT(
1806 std::cerr << "alternatives before prune:" << std::endl;
1807 print( std::cerr, candidates );
1808 )
1809
1810 CandidateList pruned;
1811 std::vector<std::string> errors;
1812 bool found = pruneCandidates( candidates, pruned, errors );
1813
1814 if ( mode.failFast && pruned.empty() ) {
1815 std::ostringstream stream;
1816 if (found) {
1817 CandidateList winners = findMinCost( candidates );
1818 stream << "Cannot choose between " << winners.size() << " alternatives for "
1819 "expression\n";
1820 ast::print( stream, expr );
1821 stream << " Alternatives are:\n";
1822 print( stream, winners, 1 );
1823 SemanticError( expr->location, stream.str() );
1824 }
1825 else {
1826 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1827 for ( const auto& err : errors ) {
1828 stream << err;
1829 }
1830 SemanticError( expr->location, stream.str() );
1831 }
1832 }
1833
1834 auto oldsize = candidates.size();
1835 candidates = move( pruned );
1836
1837 PRINT(
1838 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1839 )
1840 PRINT(
1841 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1842 << std::endl;
1843 )
1844 }
1845
1846 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1847 // adjusted
1848 if ( mode.adjust ) {
1849 for ( CandidateRef & r : candidates ) {
1850 r->expr = ast::mutate_field(
1851 r->expr.get(), &ast::Expr::result,
1852 adjustExprType( r->expr->result, r->env, localSyms ) );
1853 }
1854 }
1855
1856 // Central location to handle gcc extension keyword, etc. for all expressions
1857 for ( CandidateRef & r : candidates ) {
1858 if ( r->expr->extension != expr->extension ) {
1859 r->expr.get_and_mutate()->extension = expr->extension;
1860 }
1861 }
1862}
1863
1864std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1865 const std::vector< ast::ptr< ast::Expr > > & xs
1866) {
1867 std::vector< CandidateFinder > out;
1868
1869 for ( const auto & x : xs ) {
1870 out.emplace_back( localSyms, env );
1871 out.back().find( x, ResolvMode::withAdjustment() );
1872
1873 PRINT(
1874 std::cerr << "findSubExprs" << std::endl;
1875 print( std::cerr, out.back().candidates );
1876 )
1877 }
1878
1879 return out;
1880}
1881
1882} // namespace ResolvExpr
1883
1884// Local Variables: //
1885// tab-width: 4 //
1886// mode: c++ //
1887// compile-command: "make install" //
1888// End: //
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