source: src/ResolvExpr/CandidateFinder.cpp@ 3bc69f2

ADT ast-experimental enum pthread-emulation qualifiedEnum
Last change on this file since 3bc69f2 was 39d8950, checked in by Andrew Beach <ajbeach@…>, 4 years ago

Thread global information through resolution. Non-top-level calls to the resolver have a bit of a hack but improvements would require changes to the Pass helpers.
  • Property mode set to 100644
File size: 67.9 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 "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 ResolveContext & context;
598 const ast::SymbolTable & symtab;
599 public:
600 // static size_t traceId;
601 CandidateFinder & selfFinder;
602 CandidateList & candidates;
603 const ast::TypeEnvironment & tenv;
604 ast::ptr< ast::Type > & targetType;
605
606 enum Errors {
607 NotFound,
608 NoMatch,
609 ArgsToFew,
610 ArgsToMany,
611 RetsToFew,
612 RetsToMany,
613 NoReason
614 };
615
616 struct {
617 Errors code = NotFound;
618 } reason;
619
620 Finder( CandidateFinder & f )
621 : context( f.context ), symtab( context.symtab ), selfFinder( f ),
622 candidates( f.candidates ), tenv( f.env ), targetType( f.targetType ) {}
623
624 void previsit( const ast::Node * ) { visit_children = false; }
625
626 /// Convenience to add candidate to list
627 template<typename... Args>
628 void addCandidate( Args &&... args ) {
629 candidates.emplace_back( new Candidate{ std::forward<Args>( args )... } );
630 reason.code = NoReason;
631 }
632
633 void postvisit( const ast::ApplicationExpr * applicationExpr ) {
634 addCandidate( applicationExpr, tenv );
635 }
636
637 /// Set up candidate assertions for inference
638 void inferParameters( CandidateRef & newCand, CandidateList & out ) {
639 // Set need bindings for any unbound assertions
640 UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
641 for ( auto & assn : newCand->need ) {
642 // skip already-matched assertions
643 if ( assn.second.resnSlot != 0 ) continue;
644 // assign slot for expression if needed
645 if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
646 // fix slot to assertion
647 assn.second.resnSlot = crntResnSlot;
648 }
649 // pair slot to expression
650 if ( crntResnSlot != 0 ) {
651 newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
652 }
653
654 // add to output list; assertion satisfaction will occur later
655 out.emplace_back( newCand );
656 }
657
658 /// Completes a function candidate with arguments located
659 void validateFunctionCandidate(
660 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
661 CandidateList & out
662 ) {
663 ast::ApplicationExpr * appExpr =
664 new ast::ApplicationExpr{ func->expr->location, func->expr };
665 // sum cost and accumulate arguments
666 std::deque< const ast::Expr * > args;
667 Cost cost = func->cost;
668 const ArgPack * pack = &result;
669 while ( pack->expr ) {
670 args.emplace_front( pack->expr );
671 cost += pack->cost;
672 pack = &results[pack->parent];
673 }
674 std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
675 appExpr->args = move( vargs );
676 // build and validate new candidate
677 auto newCand =
678 std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
679 PRINT(
680 std::cerr << "instantiate function success: " << appExpr << std::endl;
681 std::cerr << "need assertions:" << std::endl;
682 ast::print( std::cerr, result.need, 2 );
683 )
684 inferParameters( newCand, out );
685 }
686
687 /// Builds a list of candidates for a function, storing them in out
688 void makeFunctionCandidates(
689 const CandidateRef & func, const ast::FunctionType * funcType,
690 const ExplodedArgs_new & args, CandidateList & out
691 ) {
692 ast::OpenVarSet funcOpen;
693 ast::AssertionSet funcNeed, funcHave;
694 ast::TypeEnvironment funcEnv{ func->env };
695 makeUnifiableVars( funcType, funcOpen, funcNeed );
696 // add all type variables as open variables now so that those not used in the
697 // parameter list are still considered open
698 funcEnv.add( funcType->forall );
699
700 if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
701 // attempt to narrow based on expected target type
702 const ast::Type * returnType = funcType->returns.front();
703 if ( ! unify(
704 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, symtab )
705 ) {
706 // unification failed, do not pursue this candidate
707 return;
708 }
709 }
710
711 // iteratively build matches, one parameter at a time
712 std::vector< ArgPack > results;
713 results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
714 std::size_t genStart = 0;
715
716 // xxx - how to handle default arg after change to ftype representation?
717 if (const ast::VariableExpr * varExpr = func->expr.as<ast::VariableExpr>()) {
718 if (const ast::FunctionDecl * funcDecl = varExpr->var.as<ast::FunctionDecl>()) {
719 // function may have default args only if directly calling by name
720 // must use types on candidate however, due to RenameVars substitution
721 auto nParams = funcType->params.size();
722
723 for (size_t i=0; i<nParams; ++i) {
724 auto obj = funcDecl->params[i].strict_as<ast::ObjectDecl>();
725 if (!instantiateArgument(
726 funcType->params[i], obj->init, args, results, genStart, symtab)) return;
727 }
728 goto endMatch;
729 }
730 }
731 for ( const auto & param : funcType->params ) {
732 // Try adding the arguments corresponding to the current parameter to the existing
733 // matches
734 // no default args for indirect calls
735 if ( ! instantiateArgument(
736 param, nullptr, args, results, genStart, symtab ) ) return;
737 }
738
739 endMatch:
740 if ( funcType->isVarArgs ) {
741 // append any unused arguments to vararg pack
742 std::size_t genEnd;
743 do {
744 genEnd = results.size();
745
746 // iterate results
747 for ( std::size_t i = genStart; i < genEnd; ++i ) {
748 unsigned nextArg = results[i].nextArg;
749
750 // use remainder of exploded tuple if present
751 if ( results[i].hasExpl() ) {
752 const ExplodedArg & expl = results[i].getExpl( args );
753
754 unsigned nextExpl = results[i].nextExpl + 1;
755 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
756
757 results.emplace_back(
758 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
759 copy( results[i].need ), copy( results[i].have ),
760 copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
761 results[i].explAlt );
762
763 continue;
764 }
765
766 // finish result when out of arguments
767 if ( nextArg >= args.size() ) {
768 validateFunctionCandidate( func, results[i], results, out );
769
770 continue;
771 }
772
773 // add each possible next argument
774 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
775 const ExplodedArg & expl = args[nextArg][j];
776
777 // fresh copies of parent parameters for this iteration
778 ast::TypeEnvironment env = results[i].env;
779 ast::OpenVarSet open = results[i].open;
780
781 env.addActual( expl.env, open );
782
783 // skip empty tuple arguments by (nearly) cloning parent into next gen
784 if ( expl.exprs.empty() ) {
785 results.emplace_back(
786 results[i], move( env ), copy( results[i].need ),
787 copy( results[i].have ), move( open ), nextArg + 1,
788 expl.cost );
789
790 continue;
791 }
792
793 // add new result
794 results.emplace_back(
795 i, expl.exprs.front(), move( env ), copy( results[i].need ),
796 copy( results[i].have ), move( open ), nextArg + 1, 0, expl.cost,
797 expl.exprs.size() == 1 ? 0 : 1, j );
798 }
799 }
800
801 genStart = genEnd;
802 } while( genEnd != results.size() );
803 } else {
804 // filter out the results that don't use all the arguments
805 for ( std::size_t i = genStart; i < results.size(); ++i ) {
806 ArgPack & result = results[i];
807 if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
808 validateFunctionCandidate( func, result, results, out );
809 }
810 }
811 }
812 }
813
814 /// Adds implicit struct-conversions to the alternative list
815 void addAnonConversions( const CandidateRef & cand ) {
816 // adds anonymous member interpretations whenever an aggregate value type is seen.
817 // it's okay for the aggregate expression to have reference type -- cast it to the
818 // base type to treat the aggregate as the referenced value
819 ast::ptr< ast::Expr > aggrExpr( cand->expr );
820 ast::ptr< ast::Type > & aggrType = aggrExpr.get_and_mutate()->result;
821 cand->env.apply( aggrType );
822
823 if ( aggrType.as< ast::ReferenceType >() ) {
824 aggrExpr = new ast::CastExpr{ aggrExpr, aggrType->stripReferences() };
825 }
826
827 if ( auto structInst = aggrExpr->result.as< ast::StructInstType >() ) {
828 addAggMembers( structInst, aggrExpr, *cand, Cost::safe, "" );
829 } else if ( auto unionInst = aggrExpr->result.as< ast::UnionInstType >() ) {
830 addAggMembers( unionInst, aggrExpr, *cand, Cost::safe, "" );
831 }
832 }
833
834 /// Adds aggregate member interpretations
835 void addAggMembers(
836 const ast::BaseInstType * aggrInst, const ast::Expr * expr,
837 const Candidate & cand, const Cost & addedCost, const std::string & name
838 ) {
839 for ( const ast::Decl * decl : aggrInst->lookup( name ) ) {
840 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( decl );
841 CandidateRef newCand = std::make_shared<Candidate>(
842 cand, new ast::MemberExpr{ expr->location, dwt, expr }, addedCost );
843 // add anonymous member interpretations whenever an aggregate value type is seen
844 // as a member expression
845 addAnonConversions( newCand );
846 candidates.emplace_back( move( newCand ) );
847 }
848 }
849
850 /// Adds tuple member interpretations
851 void addTupleMembers(
852 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
853 const Cost & addedCost, const ast::Expr * member
854 ) {
855 if ( auto constantExpr = dynamic_cast< const ast::ConstantExpr * >( member ) ) {
856 // get the value of the constant expression as an int, must be between 0 and the
857 // length of the tuple to have meaning
858 long long val = constantExpr->intValue();
859 if ( val >= 0 && (unsigned long long)val < tupleType->size() ) {
860 addCandidate(
861 cand, new ast::TupleIndexExpr{ expr->location, expr, (unsigned)val },
862 addedCost );
863 }
864 }
865 }
866
867 void postvisit( const ast::UntypedExpr * untypedExpr ) {
868 std::vector< CandidateFinder > argCandidates =
869 selfFinder.findSubExprs( untypedExpr->args );
870
871 // take care of possible tuple assignments
872 // if not tuple assignment, handled as normal function call
873 Tuples::handleTupleAssignment( selfFinder, untypedExpr, argCandidates );
874
875 CandidateFinder funcFinder( context, tenv );
876 if (auto nameExpr = untypedExpr->func.as<ast::NameExpr>()) {
877 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
878 if (kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS) {
879 assertf(!argCandidates.empty(), "special function call without argument");
880 for (auto & firstArgCand: argCandidates[0]) {
881 ast::ptr<ast::Type> argType = firstArgCand->expr->result;
882 firstArgCand->env.apply(argType);
883 // strip references
884 // xxx - is this correct?
885 while (argType.as<ast::ReferenceType>()) argType = argType.as<ast::ReferenceType>()->base;
886
887 // convert 1-tuple to plain type
888 if (auto tuple = argType.as<ast::TupleType>()) {
889 if (tuple->size() == 1) {
890 argType = tuple->types[0];
891 }
892 }
893
894 // if argType is an unbound type parameter, all special functions need to be searched.
895 if (isUnboundType(argType)) {
896 funcFinder.otypeKeys.clear();
897 break;
898 }
899
900 if (argType.as<ast::PointerType>()) funcFinder.otypeKeys.insert(Mangle::Encoding::pointer);
901 else funcFinder.otypeKeys.insert(Mangle::mangle(argType, Mangle::NoGenericParams | Mangle::Type));
902 }
903 }
904 }
905 // if candidates are already produced, do not fail
906 // xxx - is it possible that handleTupleAssignment and main finder both produce candidates?
907 // this means there exists ctor/assign functions with a tuple as first parameter.
908 ResolvMode mode = {
909 true, // adjust
910 !untypedExpr->func.as<ast::NameExpr>(), // prune if not calling by name
911 selfFinder.candidates.empty() // failfast if other options are not found
912 };
913 funcFinder.find( untypedExpr->func, mode );
914 // short-circuit if no candidates
915 // if ( funcFinder.candidates.empty() ) return;
916
917 reason.code = NoMatch;
918
919 // find function operators
920 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" };
921 CandidateFinder opFinder( context, tenv );
922 // okay if there aren't any function operations
923 opFinder.find( opExpr, ResolvMode::withoutFailFast() );
924 PRINT(
925 std::cerr << "known function ops:" << std::endl;
926 print( std::cerr, opFinder.candidates, 1 );
927 )
928
929 // pre-explode arguments
930 ExplodedArgs_new argExpansions;
931 for ( const CandidateFinder & args : argCandidates ) {
932 argExpansions.emplace_back();
933 auto & argE = argExpansions.back();
934 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
935 }
936
937 // Find function matches
938 CandidateList found;
939 SemanticErrorException errors;
940 for ( CandidateRef & func : funcFinder ) {
941 try {
942 PRINT(
943 std::cerr << "working on alternative:" << std::endl;
944 print( std::cerr, *func, 2 );
945 )
946
947 // check if the type is a pointer to function
948 const ast::Type * funcResult = func->expr->result->stripReferences();
949 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
950 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
951 CandidateRef newFunc{ new Candidate{ *func } };
952 newFunc->expr =
953 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
954 makeFunctionCandidates( newFunc, function, argExpansions, found );
955 }
956 } else if (
957 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
958 ) {
959 if ( const ast::EqvClass * clz = func->env.lookup( *inst ) ) {
960 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
961 CandidateRef newFunc{ new Candidate{ *func } };
962 newFunc->expr =
963 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
964 makeFunctionCandidates( newFunc, function, argExpansions, found );
965 }
966 }
967 }
968 } catch ( SemanticErrorException & e ) { errors.append( e ); }
969 }
970
971 // Find matches on function operators `?()`
972 if ( ! opFinder.candidates.empty() ) {
973 // add exploded function alternatives to front of argument list
974 std::vector< ExplodedArg > funcE;
975 funcE.reserve( funcFinder.candidates.size() );
976 for ( const CandidateRef & func : funcFinder ) {
977 funcE.emplace_back( *func, symtab );
978 }
979 argExpansions.emplace_front( move( funcE ) );
980
981 for ( const CandidateRef & op : opFinder ) {
982 try {
983 // check if type is pointer-to-function
984 const ast::Type * opResult = op->expr->result->stripReferences();
985 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
986 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
987 CandidateRef newOp{ new Candidate{ *op} };
988 newOp->expr =
989 referenceToRvalueConversion( newOp->expr, newOp->cost );
990 makeFunctionCandidates( newOp, function, argExpansions, found );
991 }
992 }
993 } catch ( SemanticErrorException & e ) { errors.append( e ); }
994 }
995 }
996
997 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
998 // candidates
999 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
1000
1001 // Compute conversion costs
1002 for ( CandidateRef & withFunc : found ) {
1003 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
1004
1005 PRINT(
1006 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
1007 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
1008 auto function = pointer->base.strict_as< ast::FunctionType >();
1009
1010 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
1011 std::cerr << "parameters are:" << std::endl;
1012 ast::printAll( std::cerr, function->params, 2 );
1013 std::cerr << "arguments are:" << std::endl;
1014 ast::printAll( std::cerr, appExpr->args, 2 );
1015 std::cerr << "bindings are:" << std::endl;
1016 ast::print( std::cerr, withFunc->env, 2 );
1017 std::cerr << "cost is: " << withFunc->cost << std::endl;
1018 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
1019 )
1020
1021 if ( cvtCost != Cost::infinity ) {
1022 withFunc->cvtCost = cvtCost;
1023 candidates.emplace_back( move( withFunc ) );
1024 }
1025 }
1026 found = move( candidates );
1027
1028 // use a new list so that candidates are not examined by addAnonConversions twice
1029 CandidateList winners = findMinCost( found );
1030 promoteCvtCost( winners );
1031
1032 // function may return a struct/union value, in which case we need to add candidates
1033 // for implicit conversions to each of the anonymous members, which must happen after
1034 // `findMinCost`, since anon conversions are never the cheapest
1035 for ( const CandidateRef & c : winners ) {
1036 addAnonConversions( c );
1037 }
1038 spliceBegin( candidates, winners );
1039
1040 if ( candidates.empty() && targetType && ! targetType->isVoid() ) {
1041 // If resolution is unsuccessful with a target type, try again without, since it
1042 // will sometimes succeed when it wouldn't with a target type binding.
1043 // For example:
1044 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
1045 // const char * x = "hello world";
1046 // unsigned char ch = x[0];
1047 // Fails with simple return type binding (xxx -- check this!) as follows:
1048 // * T is bound to unsigned char
1049 // * (x: const char *) is unified with unsigned char *, which fails
1050 // xxx -- fix this better
1051 targetType = nullptr;
1052 postvisit( untypedExpr );
1053 }
1054 }
1055
1056 /// true if expression is an lvalue
1057 static bool isLvalue( const ast::Expr * x ) {
1058 return x->result && ( x->get_lvalue() || x->result.as< ast::ReferenceType >() );
1059 }
1060
1061 void postvisit( const ast::AddressExpr * addressExpr ) {
1062 CandidateFinder finder( context, tenv );
1063 finder.find( addressExpr->arg );
1064
1065 if( finder.candidates.empty() ) return;
1066
1067 reason.code = NoMatch;
1068
1069 for ( CandidateRef & r : finder.candidates ) {
1070 if ( ! isLvalue( r->expr ) ) continue;
1071 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
1072 }
1073 }
1074
1075 void postvisit( const ast::LabelAddressExpr * labelExpr ) {
1076 addCandidate( labelExpr, tenv );
1077 }
1078
1079 void postvisit( const ast::CastExpr * castExpr ) {
1080 ast::ptr< ast::Type > toType = castExpr->result;
1081 assert( toType );
1082 toType = resolveTypeof( toType, context );
1083 // toType = SymTab::validateType( castExpr->location, toType, symtab );
1084 toType = adjustExprType( toType, tenv, symtab );
1085
1086 CandidateFinder finder( context, tenv, toType );
1087 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1088
1089 if( !finder.candidates.empty() ) reason.code = NoMatch;
1090
1091 CandidateList matches;
1092 for ( CandidateRef & cand : finder.candidates ) {
1093 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1094 ast::OpenVarSet open( cand->open );
1095
1096 cand->env.extractOpenVars( open );
1097
1098 // It is possible that a cast can throw away some values in a multiply-valued
1099 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1100 // subexpression results that are cast directly. The candidate is invalid if it
1101 // has fewer results than there are types to cast to.
1102 int discardedValues = cand->expr->result->size() - toType->size();
1103 if ( discardedValues < 0 ) continue;
1104
1105 // unification run for side-effects
1106 unify( toType, cand->expr->result, cand->env, need, have, open, symtab );
1107 Cost thisCost =
1108 (castExpr->isGenerated == ast::GeneratedFlag::GeneratedCast)
1109 ? conversionCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env )
1110 : castCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env );
1111
1112 PRINT(
1113 std::cerr << "working on cast with result: " << toType << std::endl;
1114 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1115 std::cerr << "env: " << cand->env << std::endl;
1116 )
1117 if ( thisCost != Cost::infinity ) {
1118 PRINT(
1119 std::cerr << "has finite cost." << std::endl;
1120 )
1121 // count one safe conversion for each value that is thrown away
1122 thisCost.incSafe( discardedValues );
1123 CandidateRef newCand = std::make_shared<Candidate>(
1124 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1125 copy( cand->env ), move( open ), move( need ), cand->cost,
1126 cand->cost + thisCost );
1127 inferParameters( newCand, matches );
1128 }
1129 }
1130
1131 // select first on argument cost, then conversion cost
1132 CandidateList minArgCost = findMinCost( matches );
1133 promoteCvtCost( minArgCost );
1134 candidates = findMinCost( minArgCost );
1135 }
1136
1137 void postvisit( const ast::VirtualCastExpr * castExpr ) {
1138 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1139 CandidateFinder finder( context, tenv );
1140 // don't prune here, all alternatives guaranteed to have same type
1141 finder.find( castExpr->arg, ResolvMode::withoutPrune() );
1142 for ( CandidateRef & r : finder.candidates ) {
1143 addCandidate(
1144 *r,
1145 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
1146 }
1147 }
1148
1149 void postvisit( const ast::KeywordCastExpr * castExpr ) {
1150 const auto & loc = castExpr->location;
1151 assertf( castExpr->result, "Cast target should have been set in Validate." );
1152 auto ref = castExpr->result.strict_as<ast::ReferenceType>();
1153 auto inst = ref->base.strict_as<ast::StructInstType>();
1154 auto target = inst->base.get();
1155
1156 CandidateFinder finder( context, tenv );
1157
1158 auto pick_alternatives = [target, this](CandidateList & found, bool expect_ref) {
1159 for(auto & cand : found) {
1160 const ast::Type * expr = cand->expr->result.get();
1161 if(expect_ref) {
1162 auto res = dynamic_cast<const ast::ReferenceType*>(expr);
1163 if(!res) { continue; }
1164 expr = res->base.get();
1165 }
1166
1167 if(auto insttype = dynamic_cast<const ast::TypeInstType*>(expr)) {
1168 auto td = cand->env.lookup(*insttype);
1169 if(!td) { continue; }
1170 expr = td->bound.get();
1171 }
1172
1173 if(auto base = dynamic_cast<const ast::StructInstType*>(expr)) {
1174 if(base->base == target) {
1175 candidates.push_back( std::move(cand) );
1176 reason.code = NoReason;
1177 }
1178 }
1179 }
1180 };
1181
1182 try {
1183 // Attempt 1 : turn (thread&)X into (thread$&)X.__thrd
1184 // Clone is purely for memory management
1185 std::unique_ptr<const ast::Expr> tech1 { new ast::UntypedMemberExpr(loc, new ast::NameExpr(loc, castExpr->concrete_target.field), castExpr->arg) };
1186
1187 // don't prune here, since it's guaranteed all alternatives will have the same type
1188 finder.find( tech1.get(), ResolvMode::withoutPrune() );
1189 pick_alternatives(finder.candidates, false);
1190
1191 return;
1192 } catch(SemanticErrorException & ) {}
1193
1194 // Fallback : turn (thread&)X into (thread$&)get_thread(X)
1195 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 })) };
1196 // don't prune here, since it's guaranteed all alternatives will have the same type
1197 finder.find( fallback.get(), ResolvMode::withoutPrune() );
1198
1199 pick_alternatives(finder.candidates, true);
1200
1201 // Whatever happens here, we have no more fallbacks
1202 }
1203
1204 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
1205 CandidateFinder aggFinder( context, tenv );
1206 aggFinder.find( memberExpr->aggregate, ResolvMode::withAdjustment() );
1207 for ( CandidateRef & agg : aggFinder.candidates ) {
1208 // it's okay for the aggregate expression to have reference type -- cast it to the
1209 // base type to treat the aggregate as the referenced value
1210 Cost addedCost = Cost::zero;
1211 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1212
1213 // find member of the given type
1214 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1215 addAggMembers(
1216 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1217 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1218 addAggMembers(
1219 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1220 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1221 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1222 }
1223 }
1224 }
1225
1226 void postvisit( const ast::MemberExpr * memberExpr ) {
1227 addCandidate( memberExpr, tenv );
1228 }
1229
1230 void postvisit( const ast::NameExpr * nameExpr ) {
1231 std::vector< ast::SymbolTable::IdData > declList;
1232 if (!selfFinder.otypeKeys.empty()) {
1233 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
1234 assertf(kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS, "special lookup with non-special target: %s", nameExpr->name.c_str());
1235
1236 for (auto & otypeKey: selfFinder.otypeKeys) {
1237 auto result = symtab.specialLookupId(kind, otypeKey);
1238 declList.insert(declList.end(), std::make_move_iterator(result.begin()), std::make_move_iterator(result.end()));
1239 }
1240 }
1241 else {
1242 declList = symtab.lookupId( nameExpr->name );
1243 }
1244 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1245
1246 if( declList.empty() ) return;
1247
1248 reason.code = NoMatch;
1249
1250 for ( auto & data : declList ) {
1251 Cost cost = Cost::zero;
1252 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1253
1254 CandidateRef newCand = std::make_shared<Candidate>(
1255 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, Cost::zero,
1256 cost );
1257 PRINT(
1258 std::cerr << "decl is ";
1259 ast::print( std::cerr, data.id );
1260 std::cerr << std::endl;
1261 std::cerr << "newExpr is ";
1262 ast::print( std::cerr, newExpr );
1263 std::cerr << std::endl;
1264 )
1265 newCand->expr = ast::mutate_field(
1266 newCand->expr.get(), &ast::Expr::result,
1267 renameTyVars( newCand->expr->result ) );
1268 // add anonymous member interpretations whenever an aggregate value type is seen
1269 // as a name expression
1270 addAnonConversions( newCand );
1271 candidates.emplace_back( move( newCand ) );
1272 }
1273 }
1274
1275 void postvisit( const ast::VariableExpr * variableExpr ) {
1276 // not sufficient to just pass `variableExpr` here, type might have changed since
1277 // creation
1278 addCandidate(
1279 new ast::VariableExpr{ variableExpr->location, variableExpr->var }, tenv );
1280 }
1281
1282 void postvisit( const ast::ConstantExpr * constantExpr ) {
1283 addCandidate( constantExpr, tenv );
1284 }
1285
1286 void postvisit( const ast::SizeofExpr * sizeofExpr ) {
1287 if ( sizeofExpr->type ) {
1288 addCandidate(
1289 new ast::SizeofExpr{
1290 sizeofExpr->location, resolveTypeof( sizeofExpr->type, context ) },
1291 tenv );
1292 } else {
1293 // find all candidates for the argument to sizeof
1294 CandidateFinder finder( context, tenv );
1295 finder.find( sizeofExpr->expr );
1296 // find the lowest-cost candidate, otherwise ambiguous
1297 CandidateList winners = findMinCost( finder.candidates );
1298 if ( winners.size() != 1 ) {
1299 SemanticError(
1300 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1301 }
1302 // return the lowest-cost candidate
1303 CandidateRef & choice = winners.front();
1304 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1305 choice->cost = Cost::zero;
1306 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1307 }
1308 }
1309
1310 void postvisit( const ast::AlignofExpr * alignofExpr ) {
1311 if ( alignofExpr->type ) {
1312 addCandidate(
1313 new ast::AlignofExpr{
1314 alignofExpr->location, resolveTypeof( alignofExpr->type, context ) },
1315 tenv );
1316 } else {
1317 // find all candidates for the argument to alignof
1318 CandidateFinder finder( context, tenv );
1319 finder.find( alignofExpr->expr );
1320 // find the lowest-cost candidate, otherwise ambiguous
1321 CandidateList winners = findMinCost( finder.candidates );
1322 if ( winners.size() != 1 ) {
1323 SemanticError(
1324 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1325 }
1326 // return the lowest-cost candidate
1327 CandidateRef & choice = winners.front();
1328 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1329 choice->cost = Cost::zero;
1330 addCandidate(
1331 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1332 }
1333 }
1334
1335 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
1336 const ast::BaseInstType * aggInst;
1337 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1338 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1339 else return;
1340
1341 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1342 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1343 addCandidate(
1344 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1345 }
1346 }
1347
1348 void postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1349 addCandidate( offsetofExpr, tenv );
1350 }
1351
1352 void postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1353 addCandidate( offsetPackExpr, tenv );
1354 }
1355
1356 void postvisit( const ast::LogicalExpr * logicalExpr ) {
1357 CandidateFinder finder1( context, tenv );
1358 finder1.find( logicalExpr->arg1, ResolvMode::withAdjustment() );
1359 if ( finder1.candidates.empty() ) return;
1360
1361 CandidateFinder finder2( context, tenv );
1362 finder2.find( logicalExpr->arg2, ResolvMode::withAdjustment() );
1363 if ( finder2.candidates.empty() ) return;
1364
1365 reason.code = NoMatch;
1366
1367 for ( const CandidateRef & r1 : finder1.candidates ) {
1368 for ( const CandidateRef & r2 : finder2.candidates ) {
1369 ast::TypeEnvironment env{ r1->env };
1370 env.simpleCombine( r2->env );
1371 ast::OpenVarSet open{ r1->open };
1372 mergeOpenVars( open, r2->open );
1373 ast::AssertionSet need;
1374 mergeAssertionSet( need, r1->need );
1375 mergeAssertionSet( need, r2->need );
1376
1377 addCandidate(
1378 new ast::LogicalExpr{
1379 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
1380 move( env ), move( open ), move( need ), r1->cost + r2->cost );
1381 }
1382 }
1383 }
1384
1385 void postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1386 // candidates for condition
1387 CandidateFinder finder1( context, tenv );
1388 finder1.find( conditionalExpr->arg1, ResolvMode::withAdjustment() );
1389 if ( finder1.candidates.empty() ) return;
1390
1391 // candidates for true result
1392 CandidateFinder finder2( context, tenv );
1393 finder2.find( conditionalExpr->arg2, ResolvMode::withAdjustment() );
1394 if ( finder2.candidates.empty() ) return;
1395
1396 // candidates for false result
1397 CandidateFinder finder3( context, tenv );
1398 finder3.find( conditionalExpr->arg3, ResolvMode::withAdjustment() );
1399 if ( finder3.candidates.empty() ) return;
1400
1401 reason.code = NoMatch;
1402
1403 for ( const CandidateRef & r1 : finder1.candidates ) {
1404 for ( const CandidateRef & r2 : finder2.candidates ) {
1405 for ( const CandidateRef & r3 : finder3.candidates ) {
1406 ast::TypeEnvironment env{ r1->env };
1407 env.simpleCombine( r2->env );
1408 env.simpleCombine( r3->env );
1409 ast::OpenVarSet open{ r1->open };
1410 mergeOpenVars( open, r2->open );
1411 mergeOpenVars( open, r3->open );
1412 ast::AssertionSet need;
1413 mergeAssertionSet( need, r1->need );
1414 mergeAssertionSet( need, r2->need );
1415 mergeAssertionSet( need, r3->need );
1416 ast::AssertionSet have;
1417
1418 // unify true and false results, then infer parameters to produce new
1419 // candidates
1420 ast::ptr< ast::Type > common;
1421 if (
1422 unify(
1423 r2->expr->result, r3->expr->result, env, need, have, open, symtab,
1424 common )
1425 ) {
1426 // generate typed expression
1427 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1428 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1429 newExpr->result = common ? common : r2->expr->result;
1430 // convert both options to result type
1431 Cost cost = r1->cost + r2->cost + r3->cost;
1432 newExpr->arg2 = computeExpressionConversionCost(
1433 newExpr->arg2, newExpr->result, symtab, env, cost );
1434 newExpr->arg3 = computeExpressionConversionCost(
1435 newExpr->arg3, newExpr->result, symtab, env, cost );
1436 // output candidate
1437 CandidateRef newCand = std::make_shared<Candidate>(
1438 newExpr, move( env ), move( open ), move( need ), cost );
1439 inferParameters( newCand, candidates );
1440 }
1441 }
1442 }
1443 }
1444 }
1445
1446 void postvisit( const ast::CommaExpr * commaExpr ) {
1447 ast::TypeEnvironment env{ tenv };
1448 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, context, env );
1449
1450 CandidateFinder finder2( context, env );
1451 finder2.find( commaExpr->arg2, ResolvMode::withAdjustment() );
1452
1453 for ( const CandidateRef & r2 : finder2.candidates ) {
1454 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1455 }
1456 }
1457
1458 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1459 addCandidate( ctorExpr, tenv );
1460 }
1461
1462 void postvisit( const ast::ConstructorExpr * ctorExpr ) {
1463 CandidateFinder finder( context, tenv );
1464 finder.find( ctorExpr->callExpr, ResolvMode::withoutPrune() );
1465 for ( CandidateRef & r : finder.candidates ) {
1466 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1467 }
1468 }
1469
1470 void postvisit( const ast::RangeExpr * rangeExpr ) {
1471 // resolve low and high, accept candidates where low and high types unify
1472 CandidateFinder finder1( context, tenv );
1473 finder1.find( rangeExpr->low, ResolvMode::withAdjustment() );
1474 if ( finder1.candidates.empty() ) return;
1475
1476 CandidateFinder finder2( context, tenv );
1477 finder2.find( rangeExpr->high, ResolvMode::withAdjustment() );
1478 if ( finder2.candidates.empty() ) return;
1479
1480 reason.code = NoMatch;
1481
1482 for ( const CandidateRef & r1 : finder1.candidates ) {
1483 for ( const CandidateRef & r2 : finder2.candidates ) {
1484 ast::TypeEnvironment env{ r1->env };
1485 env.simpleCombine( r2->env );
1486 ast::OpenVarSet open{ r1->open };
1487 mergeOpenVars( open, r2->open );
1488 ast::AssertionSet need;
1489 mergeAssertionSet( need, r1->need );
1490 mergeAssertionSet( need, r2->need );
1491 ast::AssertionSet have;
1492
1493 ast::ptr< ast::Type > common;
1494 if (
1495 unify(
1496 r1->expr->result, r2->expr->result, env, need, have, open, symtab,
1497 common )
1498 ) {
1499 // generate new expression
1500 ast::RangeExpr * newExpr =
1501 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1502 newExpr->result = common ? common : r1->expr->result;
1503 // add candidate
1504 CandidateRef newCand = std::make_shared<Candidate>(
1505 newExpr, move( env ), move( open ), move( need ),
1506 r1->cost + r2->cost );
1507 inferParameters( newCand, candidates );
1508 }
1509 }
1510 }
1511 }
1512
1513 void postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1514 std::vector< CandidateFinder > subCandidates =
1515 selfFinder.findSubExprs( tupleExpr->exprs );
1516 std::vector< CandidateList > possibilities;
1517 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1518
1519 for ( const CandidateList & subs : possibilities ) {
1520 std::vector< ast::ptr< ast::Expr > > exprs;
1521 exprs.reserve( subs.size() );
1522 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1523
1524 ast::TypeEnvironment env;
1525 ast::OpenVarSet open;
1526 ast::AssertionSet need;
1527 for ( const CandidateRef & sub : subs ) {
1528 env.simpleCombine( sub->env );
1529 mergeOpenVars( open, sub->open );
1530 mergeAssertionSet( need, sub->need );
1531 }
1532
1533 addCandidate(
1534 new ast::TupleExpr{ tupleExpr->location, move( exprs ) },
1535 move( env ), move( open ), move( need ), sumCost( subs ) );
1536 }
1537 }
1538
1539 void postvisit( const ast::TupleExpr * tupleExpr ) {
1540 addCandidate( tupleExpr, tenv );
1541 }
1542
1543 void postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1544 addCandidate( tupleExpr, tenv );
1545 }
1546
1547 void postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1548 addCandidate( tupleExpr, tenv );
1549 }
1550
1551 void postvisit( const ast::UniqueExpr * unqExpr ) {
1552 CandidateFinder finder( context, tenv );
1553 finder.find( unqExpr->expr, ResolvMode::withAdjustment() );
1554 for ( CandidateRef & r : finder.candidates ) {
1555 // ensure that the the id is passed on so that the expressions are "linked"
1556 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1557 }
1558 }
1559
1560 void postvisit( const ast::StmtExpr * stmtExpr ) {
1561 addCandidate( resolveStmtExpr( stmtExpr, context ), tenv );
1562 }
1563
1564 void postvisit( const ast::UntypedInitExpr * initExpr ) {
1565 // handle each option like a cast
1566 CandidateList matches;
1567 PRINT(
1568 std::cerr << "untyped init expr: " << initExpr << std::endl;
1569 )
1570 // O(n^2) checks of d-types with e-types
1571 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1572 // calculate target type
1573 const ast::Type * toType = resolveTypeof( initAlt.type, context );
1574 // toType = SymTab::validateType( initExpr->location, toType, symtab );
1575 toType = adjustExprType( toType, tenv, symtab );
1576 // The call to find must occur inside this loop, otherwise polymorphic return
1577 // types are not bound to the initialization type, since return type variables are
1578 // only open for the duration of resolving the UntypedExpr.
1579 CandidateFinder finder( context, tenv, toType );
1580 finder.find( initExpr->expr, ResolvMode::withAdjustment() );
1581 for ( CandidateRef & cand : finder.candidates ) {
1582 if(reason.code == NotFound) reason.code = NoMatch;
1583
1584 ast::TypeEnvironment env{ cand->env };
1585 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1586 ast::OpenVarSet open{ cand->open };
1587
1588 PRINT(
1589 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1590 )
1591
1592 // It is possible that a cast can throw away some values in a multiply-valued
1593 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1594 // the subexpression results that are cast directly. The candidate is invalid
1595 // if it has fewer results than there are types to cast to.
1596 int discardedValues = cand->expr->result->size() - toType->size();
1597 if ( discardedValues < 0 ) continue;
1598
1599 // unification run for side-effects
1600 bool canUnify = unify( toType, cand->expr->result, env, need, have, open, symtab );
1601 (void) canUnify;
1602 Cost thisCost = computeConversionCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1603 symtab, env );
1604 PRINT(
1605 Cost legacyCost = castCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1606 symtab, env );
1607 std::cerr << "Considering initialization:";
1608 std::cerr << std::endl << " FROM: " << cand->expr->result << std::endl;
1609 std::cerr << std::endl << " TO: " << toType << std::endl;
1610 std::cerr << std::endl << " Unification " << (canUnify ? "succeeded" : "failed");
1611 std::cerr << std::endl << " Legacy cost " << legacyCost;
1612 std::cerr << std::endl << " New cost " << thisCost;
1613 std::cerr << std::endl;
1614 )
1615 if ( thisCost != Cost::infinity ) {
1616 // count one safe conversion for each value that is thrown away
1617 thisCost.incSafe( discardedValues );
1618 CandidateRef newCand = std::make_shared<Candidate>(
1619 new ast::InitExpr{
1620 initExpr->location, restructureCast( cand->expr, toType ),
1621 initAlt.designation },
1622 move(env), move( open ), move( need ), cand->cost, thisCost );
1623 inferParameters( newCand, matches );
1624 }
1625 }
1626
1627 }
1628
1629 // select first on argument cost, then conversion cost
1630 CandidateList minArgCost = findMinCost( matches );
1631 promoteCvtCost( minArgCost );
1632 candidates = findMinCost( minArgCost );
1633 }
1634
1635 void postvisit( const ast::InitExpr * ) {
1636 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1637 }
1638
1639 void postvisit( const ast::DeletedExpr * ) {
1640 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1641 }
1642
1643 void postvisit( const ast::GenericExpr * ) {
1644 assertf( false, "_Generic is not yet supported." );
1645 }
1646 };
1647
1648 // size_t Finder::traceId = Stats::Heap::new_stacktrace_id("Finder");
1649 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1650 /// return type. Skips ambiguous candidates.
1651
1652} // anonymous namespace
1653
1654bool CandidateFinder::pruneCandidates( CandidateList & candidates, CandidateList & out, std::vector<std::string> & errors ) {
1655 struct PruneStruct {
1656 CandidateRef candidate;
1657 bool ambiguous;
1658
1659 PruneStruct() = default;
1660 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1661 };
1662
1663 // find lowest-cost candidate for each type
1664 std::unordered_map< std::string, PruneStruct > selected;
1665 // attempt to skip satisfyAssertions on more expensive alternatives if better options have been found
1666 std::sort(candidates.begin(), candidates.end(), [](const CandidateRef & x, const CandidateRef & y){return x->cost < y->cost;});
1667 for ( CandidateRef & candidate : candidates ) {
1668 std::string mangleName;
1669 {
1670 ast::ptr< ast::Type > newType = candidate->expr->result;
1671 assertf(candidate->expr->result, "Result of expression %p for candidate is null", candidate->expr.get());
1672 candidate->env.apply( newType );
1673 mangleName = Mangle::mangle( newType );
1674 }
1675
1676 auto found = selected.find( mangleName );
1677 if (found != selected.end() && found->second.candidate->cost < candidate->cost) {
1678 PRINT(
1679 std::cerr << "cost " << candidate->cost << " loses to "
1680 << found->second.candidate->cost << std::endl;
1681 )
1682 continue;
1683 }
1684
1685 // xxx - when do satisfyAssertions produce more than 1 result?
1686 // this should only happen when initial result type contains
1687 // unbound type parameters, then it should never be pruned by
1688 // the previous step, since renameTyVars guarantees the mangled name
1689 // is unique.
1690 CandidateList satisfied;
1691 bool needRecomputeKey = false;
1692 if (candidate->need.empty()) {
1693 satisfied.emplace_back(candidate);
1694 }
1695 else {
1696 satisfyAssertions(candidate, context.symtab, satisfied, errors);
1697 needRecomputeKey = true;
1698 }
1699
1700 for (auto & newCand : satisfied) {
1701 // recomputes type key, if satisfyAssertions changed it
1702 if (needRecomputeKey)
1703 {
1704 ast::ptr< ast::Type > newType = newCand->expr->result;
1705 assertf(newCand->expr->result, "Result of expression %p for candidate is null", newCand->expr.get());
1706 newCand->env.apply( newType );
1707 mangleName = Mangle::mangle( newType );
1708 }
1709 auto found = selected.find( mangleName );
1710 if ( found != selected.end() ) {
1711 if ( newCand->cost < found->second.candidate->cost ) {
1712 PRINT(
1713 std::cerr << "cost " << newCand->cost << " beats "
1714 << found->second.candidate->cost << std::endl;
1715 )
1716
1717 found->second = PruneStruct{ newCand };
1718 } else if ( newCand->cost == found->second.candidate->cost ) {
1719 // if one of the candidates contains a deleted identifier, can pick the other,
1720 // since deleted expressions should not be ambiguous if there is another option
1721 // that is at least as good
1722 if ( findDeletedExpr( newCand->expr ) ) {
1723 // do nothing
1724 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1725 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1726 PRINT( std::cerr << "current is deleted" << std::endl; )
1727 found->second = PruneStruct{ newCand };
1728 } else {
1729 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1730 found->second.ambiguous = true;
1731 }
1732 } else {
1733 // xxx - can satisfyAssertions increase the cost?
1734 PRINT(
1735 std::cerr << "cost " << newCand->cost << " loses to "
1736 << found->second.candidate->cost << std::endl;
1737 )
1738 }
1739 } else {
1740 selected.emplace_hint( found, mangleName, newCand );
1741 }
1742 }
1743 }
1744
1745 // report unambiguous min-cost candidates
1746 // CandidateList out;
1747 for ( auto & target : selected ) {
1748 if ( target.second.ambiguous ) continue;
1749
1750 CandidateRef cand = target.second.candidate;
1751
1752 ast::ptr< ast::Type > newResult = cand->expr->result;
1753 cand->env.applyFree( newResult );
1754 cand->expr = ast::mutate_field(
1755 cand->expr.get(), &ast::Expr::result, move( newResult ) );
1756
1757 out.emplace_back( cand );
1758 }
1759 // if everything is lost in satisfyAssertions, report the error
1760 return !selected.empty();
1761}
1762
1763void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
1764 // Find alternatives for expression
1765 ast::Pass<Finder> finder{ *this };
1766 expr->accept( finder );
1767
1768 if ( mode.failFast && candidates.empty() ) {
1769 switch(finder.core.reason.code) {
1770 case Finder::NotFound:
1771 { SemanticError( expr, "No alternatives for expression " ); break; }
1772 case Finder::NoMatch:
1773 { SemanticError( expr, "Invalid application of existing declaration(s) in expression " ); break; }
1774 case Finder::ArgsToFew:
1775 case Finder::ArgsToMany:
1776 case Finder::RetsToFew:
1777 case Finder::RetsToMany:
1778 case Finder::NoReason:
1779 default:
1780 { SemanticError( expr->location, "No reasonable alternatives for expression : reasons unkown" ); }
1781 }
1782 }
1783
1784 /*
1785 if ( mode.satisfyAssns || mode.prune ) {
1786 // trim candidates to just those where the assertions are satisfiable
1787 // - necessary pre-requisite to pruning
1788 CandidateList satisfied;
1789 std::vector< std::string > errors;
1790 for ( CandidateRef & candidate : candidates ) {
1791 satisfyAssertions( candidate, localSyms, satisfied, errors );
1792 }
1793
1794 // fail early if none such
1795 if ( mode.failFast && satisfied.empty() ) {
1796 std::ostringstream stream;
1797 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1798 for ( const auto& err : errors ) {
1799 stream << err;
1800 }
1801 SemanticError( expr->location, stream.str() );
1802 }
1803
1804 // reset candidates
1805 candidates = move( satisfied );
1806 }
1807 */
1808
1809 if ( mode.prune ) {
1810 // trim candidates to single best one
1811 PRINT(
1812 std::cerr << "alternatives before prune:" << std::endl;
1813 print( std::cerr, candidates );
1814 )
1815
1816 CandidateList pruned;
1817 std::vector<std::string> errors;
1818 bool found = pruneCandidates( candidates, pruned, errors );
1819
1820 if ( mode.failFast && pruned.empty() ) {
1821 std::ostringstream stream;
1822 if (found) {
1823 CandidateList winners = findMinCost( candidates );
1824 stream << "Cannot choose between " << winners.size() << " alternatives for "
1825 "expression\n";
1826 ast::print( stream, expr );
1827 stream << " Alternatives are:\n";
1828 print( stream, winners, 1 );
1829 SemanticError( expr->location, stream.str() );
1830 }
1831 else {
1832 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1833 for ( const auto& err : errors ) {
1834 stream << err;
1835 }
1836 SemanticError( expr->location, stream.str() );
1837 }
1838 }
1839
1840 auto oldsize = candidates.size();
1841 candidates = move( pruned );
1842
1843 PRINT(
1844 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1845 )
1846 PRINT(
1847 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1848 << std::endl;
1849 )
1850 }
1851
1852 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1853 // adjusted
1854 if ( mode.adjust ) {
1855 for ( CandidateRef & r : candidates ) {
1856 r->expr = ast::mutate_field(
1857 r->expr.get(), &ast::Expr::result,
1858 adjustExprType( r->expr->result, r->env, context.symtab ) );
1859 }
1860 }
1861
1862 // Central location to handle gcc extension keyword, etc. for all expressions
1863 for ( CandidateRef & r : candidates ) {
1864 if ( r->expr->extension != expr->extension ) {
1865 r->expr.get_and_mutate()->extension = expr->extension;
1866 }
1867 }
1868}
1869
1870std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1871 const std::vector< ast::ptr< ast::Expr > > & xs
1872) {
1873 std::vector< CandidateFinder > out;
1874
1875 for ( const auto & x : xs ) {
1876 out.emplace_back( context, env );
1877 out.back().find( x, ResolvMode::withAdjustment() );
1878
1879 PRINT(
1880 std::cerr << "findSubExprs" << std::endl;
1881 print( std::cerr, out.back().candidates );
1882 )
1883 }
1884
1885 return out;
1886}
1887
1888} // namespace ResolvExpr
1889
1890// Local Variables: //
1891// tab-width: 4 //
1892// mode: c++ //
1893// compile-command: "make install" //
1894// End: //
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