1 //===- Overload.h - C++ Overloading -----------------------------*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file defines the data structures and types used in C++
10 // overload resolution.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CLANG_SEMA_OVERLOAD_H
15 #define LLVM_CLANG_SEMA_OVERLOAD_H
17 #include "clang/AST/Decl.h"
18 #include "clang/AST/DeclAccessPair.h"
19 #include "clang/AST/DeclBase.h"
20 #include "clang/AST/DeclCXX.h"
21 #include "clang/AST/DeclTemplate.h"
22 #include "clang/AST/Expr.h"
23 #include "clang/AST/Type.h"
24 #include "clang/Basic/LLVM.h"
25 #include "clang/Basic/SourceLocation.h"
26 #include "clang/Sema/SemaFixItUtils.h"
27 #include "clang/Sema/TemplateDeduction.h"
28 #include "llvm/ADT/ArrayRef.h"
29 #include "llvm/ADT/None.h"
30 #include "llvm/ADT/STLExtras.h"
31 #include "llvm/ADT/SmallPtrSet.h"
32 #include "llvm/ADT/SmallVector.h"
33 #include "llvm/ADT/StringRef.h"
34 #include "llvm/Support/AlignOf.h"
35 #include "llvm/Support/Allocator.h"
36 #include "llvm/Support/Casting.h"
37 #include "llvm/Support/ErrorHandling.h"
49 /// OverloadingResult - Capture the result of performing overload
51 enum OverloadingResult {
52 /// Overload resolution succeeded.
55 /// No viable function found.
56 OR_No_Viable_Function,
58 /// Ambiguous candidates found.
61 /// Succeeded, but refers to a deleted function.
65 enum OverloadCandidateDisplayKind {
66 /// Requests that all candidates be shown. Viable candidates will
70 /// Requests that only viable candidates be shown.
73 /// Requests that only tied-for-best candidates be shown.
74 OCD_AmbiguousCandidates
77 /// The parameter ordering that will be used for the candidate. This is
78 /// used to represent C++20 binary operator rewrites that reverse the order
79 /// of the arguments. If the parameter ordering is Reversed, the Args list is
80 /// reversed (but obviously the ParamDecls for the function are not).
82 /// After forming an OverloadCandidate with reversed parameters, the list
83 /// of conversions will (as always) be indexed by argument, so will be
84 /// in reverse parameter order.
85 enum class OverloadCandidateParamOrder : char { Normal, Reversed };
87 /// The kinds of rewrite we perform on overload candidates. Note that the
88 /// values here are chosen to serve as both bitflags and as a rank (lower
89 /// values are preferred by overload resolution).
90 enum OverloadCandidateRewriteKind : unsigned {
91 /// Candidate is not a rewritten candidate.
94 /// Candidate is a rewritten candidate with a different operator name.
95 CRK_DifferentOperator = 0x1,
97 /// Candidate is a rewritten candidate with a reversed order of parameters.
101 /// ImplicitConversionKind - The kind of implicit conversion used to
102 /// convert an argument to a parameter's type. The enumerator values
103 /// match with the table titled 'Conversions' in [over.ics.scs] and are listed
104 /// such that better conversion kinds have smaller values.
105 enum ImplicitConversionKind {
106 /// Identity conversion (no conversion)
109 /// Lvalue-to-rvalue conversion (C++ [conv.lval])
110 ICK_Lvalue_To_Rvalue,
112 /// Array-to-pointer conversion (C++ [conv.array])
113 ICK_Array_To_Pointer,
115 /// Function-to-pointer (C++ [conv.array])
116 ICK_Function_To_Pointer,
118 /// Function pointer conversion (C++17 [conv.fctptr])
119 ICK_Function_Conversion,
121 /// Qualification conversions (C++ [conv.qual])
124 /// Integral promotions (C++ [conv.prom])
125 ICK_Integral_Promotion,
127 /// Floating point promotions (C++ [conv.fpprom])
128 ICK_Floating_Promotion,
130 /// Complex promotions (Clang extension)
131 ICK_Complex_Promotion,
133 /// Integral conversions (C++ [conv.integral])
134 ICK_Integral_Conversion,
136 /// Floating point conversions (C++ [conv.double]
137 ICK_Floating_Conversion,
139 /// Complex conversions (C99 6.3.1.6)
140 ICK_Complex_Conversion,
142 /// Floating-integral conversions (C++ [conv.fpint])
143 ICK_Floating_Integral,
145 /// Pointer conversions (C++ [conv.ptr])
146 ICK_Pointer_Conversion,
148 /// Pointer-to-member conversions (C++ [conv.mem])
151 /// Boolean conversions (C++ [conv.bool])
152 ICK_Boolean_Conversion,
154 /// Conversions between compatible types in C99
155 ICK_Compatible_Conversion,
157 /// Derived-to-base (C++ [over.best.ics])
160 /// Vector conversions
161 ICK_Vector_Conversion,
163 /// A vector splat from an arithmetic type
166 /// Complex-real conversions (C99 6.3.1.7)
169 /// Block Pointer conversions
170 ICK_Block_Pointer_Conversion,
172 /// Transparent Union Conversions
173 ICK_TransparentUnionConversion,
175 /// Objective-C ARC writeback conversion
176 ICK_Writeback_Conversion,
178 /// Zero constant to event (OpenCL1.2 6.12.10)
179 ICK_Zero_Event_Conversion,
181 /// Zero constant to queue
182 ICK_Zero_Queue_Conversion,
184 /// Conversions allowed in C, but not C++
185 ICK_C_Only_Conversion,
187 /// C-only conversion between pointers with incompatible types
188 ICK_Incompatible_Pointer_Conversion,
190 /// The number of conversion kinds
191 ICK_Num_Conversion_Kinds,
194 /// ImplicitConversionRank - The rank of an implicit conversion
195 /// kind. The enumerator values match with Table 9 of (C++
196 /// 13.3.3.1.1) and are listed such that better conversion ranks
197 /// have smaller values.
198 enum ImplicitConversionRank {
208 /// OpenCL Scalar Widening
209 ICR_OCL_Scalar_Widening,
211 /// Complex <-> Real conversion
212 ICR_Complex_Real_Conversion,
214 /// ObjC ARC writeback conversion
215 ICR_Writeback_Conversion,
217 /// Conversion only allowed in the C standard (e.g. void* to char*).
220 /// Conversion not allowed by the C standard, but that we accept as an
221 /// extension anyway.
222 ICR_C_Conversion_Extension
225 ImplicitConversionRank GetConversionRank(ImplicitConversionKind Kind);
227 /// NarrowingKind - The kind of narrowing conversion being performed by a
228 /// standard conversion sequence according to C++11 [dcl.init.list]p7.
230 /// Not a narrowing conversion.
233 /// A narrowing conversion by virtue of the source and destination types.
236 /// A narrowing conversion, because a constant expression got narrowed.
237 NK_Constant_Narrowing,
239 /// A narrowing conversion, because a non-constant-expression variable might
240 /// have got narrowed.
241 NK_Variable_Narrowing,
243 /// Cannot tell whether this is a narrowing conversion because the
244 /// expression is value-dependent.
245 NK_Dependent_Narrowing,
248 /// StandardConversionSequence - represents a standard conversion
249 /// sequence (C++ 13.3.3.1.1). A standard conversion sequence
250 /// contains between zero and three conversions. If a particular
251 /// conversion is not needed, it will be set to the identity conversion
252 /// (ICK_Identity). Note that the three conversions are
253 /// specified as separate members (rather than in an array) so that
254 /// we can keep the size of a standard conversion sequence to a
256 class StandardConversionSequence {
258 /// First -- The first conversion can be an lvalue-to-rvalue
259 /// conversion, array-to-pointer conversion, or
260 /// function-to-pointer conversion.
261 ImplicitConversionKind First : 8;
263 /// Second - The second conversion can be an integral promotion,
264 /// floating point promotion, integral conversion, floating point
265 /// conversion, floating-integral conversion, pointer conversion,
266 /// pointer-to-member conversion, or boolean conversion.
267 ImplicitConversionKind Second : 8;
269 /// Third - The third conversion can be a qualification conversion
270 /// or a function conversion.
271 ImplicitConversionKind Third : 8;
273 /// Whether this is the deprecated conversion of a
274 /// string literal to a pointer to non-const character data
276 unsigned DeprecatedStringLiteralToCharPtr : 1;
278 /// Whether the qualification conversion involves a change in the
279 /// Objective-C lifetime (for automatic reference counting).
280 unsigned QualificationIncludesObjCLifetime : 1;
282 /// IncompatibleObjC - Whether this is an Objective-C conversion
283 /// that we should warn about (if we actually use it).
284 unsigned IncompatibleObjC : 1;
286 /// ReferenceBinding - True when this is a reference binding
287 /// (C++ [over.ics.ref]).
288 unsigned ReferenceBinding : 1;
290 /// DirectBinding - True when this is a reference binding that is a
291 /// direct binding (C++ [dcl.init.ref]).
292 unsigned DirectBinding : 1;
294 /// Whether this is an lvalue reference binding (otherwise, it's
295 /// an rvalue reference binding).
296 unsigned IsLvalueReference : 1;
298 /// Whether we're binding to a function lvalue.
299 unsigned BindsToFunctionLvalue : 1;
301 /// Whether we're binding to an rvalue.
302 unsigned BindsToRvalue : 1;
304 /// Whether this binds an implicit object argument to a
305 /// non-static member function without a ref-qualifier.
306 unsigned BindsImplicitObjectArgumentWithoutRefQualifier : 1;
308 /// Whether this binds a reference to an object with a different
309 /// Objective-C lifetime qualifier.
310 unsigned ObjCLifetimeConversionBinding : 1;
312 /// FromType - The type that this conversion is converting
313 /// from. This is an opaque pointer that can be translated into a
317 /// ToType - The types that this conversion is converting to in
318 /// each step. This is an opaque pointer that can be translated
322 /// CopyConstructor - The copy constructor that is used to perform
323 /// this conversion, when the conversion is actually just the
324 /// initialization of an object via copy constructor. Such
325 /// conversions are either identity conversions or derived-to-base
327 CXXConstructorDecl *CopyConstructor;
328 DeclAccessPair FoundCopyConstructor;
330 void setFromType(QualType T) { FromTypePtr = T.getAsOpaquePtr(); }
332 void setToType(unsigned Idx, QualType T) {
333 assert(Idx < 3 && "To type index is out of range");
334 ToTypePtrs[Idx] = T.getAsOpaquePtr();
337 void setAllToTypes(QualType T) {
338 ToTypePtrs[0] = T.getAsOpaquePtr();
339 ToTypePtrs[1] = ToTypePtrs[0];
340 ToTypePtrs[2] = ToTypePtrs[0];
343 QualType getFromType() const {
344 return QualType::getFromOpaquePtr(FromTypePtr);
347 QualType getToType(unsigned Idx) const {
348 assert(Idx < 3 && "To type index is out of range");
349 return QualType::getFromOpaquePtr(ToTypePtrs[Idx]);
352 void setAsIdentityConversion();
354 bool isIdentityConversion() const {
355 return Second == ICK_Identity && Third == ICK_Identity;
358 ImplicitConversionRank getRank() const;
360 getNarrowingKind(ASTContext &Context, const Expr *Converted,
361 APValue &ConstantValue, QualType &ConstantType,
362 bool IgnoreFloatToIntegralConversion = false) const;
363 bool isPointerConversionToBool() const;
364 bool isPointerConversionToVoidPointer(ASTContext& Context) const;
368 /// UserDefinedConversionSequence - Represents a user-defined
369 /// conversion sequence (C++ 13.3.3.1.2).
370 struct UserDefinedConversionSequence {
371 /// Represents the standard conversion that occurs before
372 /// the actual user-defined conversion.
374 /// C++11 13.3.3.1.2p1:
375 /// If the user-defined conversion is specified by a constructor
376 /// (12.3.1), the initial standard conversion sequence converts
377 /// the source type to the type required by the argument of the
378 /// constructor. If the user-defined conversion is specified by
379 /// a conversion function (12.3.2), the initial standard
380 /// conversion sequence converts the source type to the implicit
381 /// object parameter of the conversion function.
382 StandardConversionSequence Before;
384 /// EllipsisConversion - When this is true, it means user-defined
385 /// conversion sequence starts with a ... (ellipsis) conversion, instead of
386 /// a standard conversion. In this case, 'Before' field must be ignored.
387 // FIXME. I much rather put this as the first field. But there seems to be
388 // a gcc code gen. bug which causes a crash in a test. Putting it here seems
389 // to work around the crash.
390 bool EllipsisConversion : 1;
392 /// HadMultipleCandidates - When this is true, it means that the
393 /// conversion function was resolved from an overloaded set having
394 /// size greater than 1.
395 bool HadMultipleCandidates : 1;
397 /// After - Represents the standard conversion that occurs after
398 /// the actual user-defined conversion.
399 StandardConversionSequence After;
401 /// ConversionFunction - The function that will perform the
402 /// user-defined conversion. Null if the conversion is an
403 /// aggregate initialization from an initializer list.
404 FunctionDecl* ConversionFunction;
406 /// The declaration that we found via name lookup, which might be
407 /// the same as \c ConversionFunction or it might be a using declaration
408 /// that refers to \c ConversionFunction.
409 DeclAccessPair FoundConversionFunction;
414 /// Represents an ambiguous user-defined conversion sequence.
415 struct AmbiguousConversionSequence {
416 using ConversionSet =
417 SmallVector<std::pair<NamedDecl *, FunctionDecl *>, 4>;
421 char Buffer[sizeof(ConversionSet)];
423 QualType getFromType() const {
424 return QualType::getFromOpaquePtr(FromTypePtr);
427 QualType getToType() const {
428 return QualType::getFromOpaquePtr(ToTypePtr);
431 void setFromType(QualType T) { FromTypePtr = T.getAsOpaquePtr(); }
432 void setToType(QualType T) { ToTypePtr = T.getAsOpaquePtr(); }
434 ConversionSet &conversions() {
435 return *reinterpret_cast<ConversionSet*>(Buffer);
438 const ConversionSet &conversions() const {
439 return *reinterpret_cast<const ConversionSet*>(Buffer);
442 void addConversion(NamedDecl *Found, FunctionDecl *D) {
443 conversions().push_back(std::make_pair(Found, D));
446 using iterator = ConversionSet::iterator;
448 iterator begin() { return conversions().begin(); }
449 iterator end() { return conversions().end(); }
451 using const_iterator = ConversionSet::const_iterator;
453 const_iterator begin() const { return conversions().begin(); }
454 const_iterator end() const { return conversions().end(); }
458 void copyFrom(const AmbiguousConversionSequence &);
461 /// BadConversionSequence - Records information about an invalid
462 /// conversion sequence.
463 struct BadConversionSequence {
468 lvalue_ref_to_rvalue,
472 // This can be null, e.g. for implicit object arguments.
478 // The type we're converting from (an opaque QualType).
481 // The type we're converting to (an opaque QualType).
485 void init(FailureKind K, Expr *From, QualType To) {
486 init(K, From->getType(), To);
490 void init(FailureKind K, QualType From, QualType To) {
497 QualType getFromType() const { return QualType::getFromOpaquePtr(FromTy); }
498 QualType getToType() const { return QualType::getFromOpaquePtr(ToTy); }
500 void setFromExpr(Expr *E) {
502 setFromType(E->getType());
505 void setFromType(QualType T) { FromTy = T.getAsOpaquePtr(); }
506 void setToType(QualType T) { ToTy = T.getAsOpaquePtr(); }
509 /// ImplicitConversionSequence - Represents an implicit conversion
510 /// sequence, which may be a standard conversion sequence
511 /// (C++ 13.3.3.1.1), user-defined conversion sequence (C++ 13.3.3.1.2),
512 /// or an ellipsis conversion sequence (C++ 13.3.3.1.3).
513 class ImplicitConversionSequence {
515 /// Kind - The kind of implicit conversion sequence. BadConversion
516 /// specifies that there is no conversion from the source type to
517 /// the target type. AmbiguousConversion represents the unique
518 /// ambiguous conversion (C++0x [over.best.ics]p10).
520 StandardConversion = 0,
521 UserDefinedConversion,
529 Uninitialized = BadConversion + 1
532 /// ConversionKind - The kind of implicit conversion sequence.
533 unsigned ConversionKind : 30;
535 /// Whether the target is really a std::initializer_list, and the
536 /// sequence only represents the worst element conversion.
537 unsigned StdInitializerListElement : 1;
539 void setKind(Kind K) {
545 if (ConversionKind == AmbiguousConversion) Ambiguous.destruct();
550 /// When ConversionKind == StandardConversion, provides the
551 /// details of the standard conversion sequence.
552 StandardConversionSequence Standard;
554 /// When ConversionKind == UserDefinedConversion, provides the
555 /// details of the user-defined conversion sequence.
556 UserDefinedConversionSequence UserDefined;
558 /// When ConversionKind == AmbiguousConversion, provides the
559 /// details of the ambiguous conversion.
560 AmbiguousConversionSequence Ambiguous;
562 /// When ConversionKind == BadConversion, provides the details
563 /// of the bad conversion.
564 BadConversionSequence Bad;
567 ImplicitConversionSequence()
568 : ConversionKind(Uninitialized), StdInitializerListElement(false) {
569 Standard.setAsIdentityConversion();
572 ImplicitConversionSequence(const ImplicitConversionSequence &Other)
573 : ConversionKind(Other.ConversionKind),
574 StdInitializerListElement(Other.StdInitializerListElement) {
575 switch (ConversionKind) {
576 case Uninitialized: break;
577 case StandardConversion: Standard = Other.Standard; break;
578 case UserDefinedConversion: UserDefined = Other.UserDefined; break;
579 case AmbiguousConversion: Ambiguous.copyFrom(Other.Ambiguous); break;
580 case EllipsisConversion: break;
581 case BadConversion: Bad = Other.Bad; break;
585 ImplicitConversionSequence &
586 operator=(const ImplicitConversionSequence &Other) {
588 new (this) ImplicitConversionSequence(Other);
592 ~ImplicitConversionSequence() {
596 Kind getKind() const {
597 assert(isInitialized() && "querying uninitialized conversion");
598 return Kind(ConversionKind);
601 /// Return a ranking of the implicit conversion sequence
602 /// kind, where smaller ranks represent better conversion
605 /// In particular, this routine gives user-defined conversion
606 /// sequences and ambiguous conversion sequences the same rank,
607 /// per C++ [over.best.ics]p10.
608 unsigned getKindRank() const {
610 case StandardConversion:
613 case UserDefinedConversion:
614 case AmbiguousConversion:
617 case EllipsisConversion:
624 llvm_unreachable("Invalid ImplicitConversionSequence::Kind!");
627 bool isBad() const { return getKind() == BadConversion; }
628 bool isStandard() const { return getKind() == StandardConversion; }
629 bool isEllipsis() const { return getKind() == EllipsisConversion; }
630 bool isAmbiguous() const { return getKind() == AmbiguousConversion; }
631 bool isUserDefined() const { return getKind() == UserDefinedConversion; }
632 bool isFailure() const { return isBad() || isAmbiguous(); }
634 /// Determines whether this conversion sequence has been
635 /// initialized. Most operations should never need to query
636 /// uninitialized conversions and should assert as above.
637 bool isInitialized() const { return ConversionKind != Uninitialized; }
639 /// Sets this sequence as a bad conversion for an explicit argument.
640 void setBad(BadConversionSequence::FailureKind Failure,
641 Expr *FromExpr, QualType ToType) {
642 setKind(BadConversion);
643 Bad.init(Failure, FromExpr, ToType);
646 /// Sets this sequence as a bad conversion for an implicit argument.
647 void setBad(BadConversionSequence::FailureKind Failure,
648 QualType FromType, QualType ToType) {
649 setKind(BadConversion);
650 Bad.init(Failure, FromType, ToType);
653 void setStandard() { setKind(StandardConversion); }
654 void setEllipsis() { setKind(EllipsisConversion); }
655 void setUserDefined() { setKind(UserDefinedConversion); }
657 void setAmbiguous() {
658 if (ConversionKind == AmbiguousConversion) return;
659 ConversionKind = AmbiguousConversion;
660 Ambiguous.construct();
663 void setAsIdentityConversion(QualType T) {
665 Standard.setAsIdentityConversion();
666 Standard.setFromType(T);
667 Standard.setAllToTypes(T);
670 /// Whether the target is really a std::initializer_list, and the
671 /// sequence only represents the worst element conversion.
672 bool isStdInitializerListElement() const {
673 return StdInitializerListElement;
676 void setStdInitializerListElement(bool V = true) {
677 StdInitializerListElement = V;
680 // The result of a comparison between implicit conversion
681 // sequences. Use Sema::CompareImplicitConversionSequences to
682 // actually perform the comparison.
685 Indistinguishable = 0,
689 void DiagnoseAmbiguousConversion(Sema &S,
690 SourceLocation CaretLoc,
691 const PartialDiagnostic &PDiag) const;
696 enum OverloadFailureKind {
697 ovl_fail_too_many_arguments,
698 ovl_fail_too_few_arguments,
699 ovl_fail_bad_conversion,
700 ovl_fail_bad_deduction,
702 /// This conversion candidate was not considered because it
703 /// duplicates the work of a trivial or derived-to-base
705 ovl_fail_trivial_conversion,
707 /// This conversion candidate was not considered because it is
708 /// an illegal instantiation of a constructor temploid: it is
709 /// callable with one argument, we only have one argument, and
710 /// its first parameter type is exactly the type of the class.
712 /// Defining such a constructor directly is illegal, and
713 /// template-argument deduction is supposed to ignore such
714 /// instantiations, but we can still get one with the right
715 /// kind of implicit instantiation.
716 ovl_fail_illegal_constructor,
718 /// This conversion candidate is not viable because its result
719 /// type is not implicitly convertible to the desired type.
720 ovl_fail_bad_final_conversion,
722 /// This conversion function template specialization candidate is not
723 /// viable because the final conversion was not an exact match.
724 ovl_fail_final_conversion_not_exact,
726 /// (CUDA) This candidate was not viable because the callee
727 /// was not accessible from the caller's target (i.e. host->device,
728 /// global->host, device->host).
731 /// This candidate function was not viable because an enable_if
732 /// attribute disabled it.
735 /// This candidate constructor or conversion function is explicit but
736 /// the context doesn't permit explicit functions.
739 /// This candidate was not viable because its address could not be taken.
740 ovl_fail_addr_not_available,
742 /// This candidate was not viable because its OpenCL extension is disabled.
743 ovl_fail_ext_disabled,
745 /// This inherited constructor is not viable because it would slice the
747 ovl_fail_inhctor_slice,
749 /// This candidate was not viable because it is a non-default multiversioned
751 ovl_non_default_multiversion_function,
753 /// This constructor/conversion candidate fail due to an address space
754 /// mismatch between the object being constructed and the overload
756 ovl_fail_object_addrspace_mismatch,
758 /// This candidate was not viable because its associated constraints were
760 ovl_fail_constraints_not_satisfied,
763 /// A list of implicit conversion sequences for the arguments of an
764 /// OverloadCandidate.
765 using ConversionSequenceList =
766 llvm::MutableArrayRef<ImplicitConversionSequence>;
768 /// OverloadCandidate - A single candidate in an overload set (C++ 13.3).
769 struct OverloadCandidate {
770 /// Function - The actual function that this candidate
771 /// represents. When NULL, this is a built-in candidate
772 /// (C++ [over.oper]) or a surrogate for a conversion to a
773 /// function pointer or reference (C++ [over.call.object]).
774 FunctionDecl *Function;
776 /// FoundDecl - The original declaration that was looked up /
777 /// invented / otherwise found, together with its access.
778 /// Might be a UsingShadowDecl or a FunctionTemplateDecl.
779 DeclAccessPair FoundDecl;
781 /// BuiltinParamTypes - Provides the parameter types of a built-in overload
782 /// candidate. Only valid when Function is NULL.
783 QualType BuiltinParamTypes[3];
785 /// Surrogate - The conversion function for which this candidate
786 /// is a surrogate, but only if IsSurrogate is true.
787 CXXConversionDecl *Surrogate;
789 /// The conversion sequences used to convert the function arguments
790 /// to the function parameters. Note that these are indexed by argument,
791 /// so may not match the parameter order of Function.
792 ConversionSequenceList Conversions;
794 /// The FixIt hints which can be used to fix the Bad candidate.
795 ConversionFixItGenerator Fix;
797 /// Viable - True to indicate that this overload candidate is viable.
800 /// Whether this candidate is the best viable function, or tied for being
801 /// the best viable function.
803 /// For an ambiguous overload resolution, indicates whether this candidate
804 /// was part of the ambiguity kernel: the minimal non-empty set of viable
805 /// candidates such that all elements of the ambiguity kernel are better
806 /// than all viable candidates not in the ambiguity kernel.
809 /// IsSurrogate - True to indicate that this candidate is a
810 /// surrogate for a conversion to a function pointer or reference
811 /// (C++ [over.call.object]).
812 bool IsSurrogate : 1;
814 /// IgnoreObjectArgument - True to indicate that the first
815 /// argument's conversion, which for this function represents the
816 /// implicit object argument, should be ignored. This will be true
817 /// when the candidate is a static member function (where the
818 /// implicit object argument is just a placeholder) or a
819 /// non-static member function when the call doesn't have an
821 bool IgnoreObjectArgument : 1;
823 /// True if the candidate was found using ADL.
824 CallExpr::ADLCallKind IsADLCandidate : 1;
826 /// Whether this is a rewritten candidate, and if so, of what kind?
827 unsigned RewriteKind : 2;
829 /// FailureKind - The reason why this candidate is not viable.
830 /// Actually an OverloadFailureKind.
831 unsigned char FailureKind;
833 /// The number of call arguments that were explicitly provided,
834 /// to be used while performing partial ordering of function templates.
835 unsigned ExplicitCallArguments;
838 DeductionFailureInfo DeductionFailure;
840 /// FinalConversion - For a conversion function (where Function is
841 /// a CXXConversionDecl), the standard conversion that occurs
842 /// after the call to the overload candidate to convert the result
843 /// of calling the conversion function to the required type.
844 StandardConversionSequence FinalConversion;
847 /// Get RewriteKind value in OverloadCandidateRewriteKind type (This
848 /// function is to workaround the spurious GCC bitfield enum warning)
849 OverloadCandidateRewriteKind getRewriteKind() const {
850 return static_cast<OverloadCandidateRewriteKind>(RewriteKind);
853 /// hasAmbiguousConversion - Returns whether this overload
854 /// candidate requires an ambiguous conversion or not.
855 bool hasAmbiguousConversion() const {
856 for (auto &C : Conversions) {
857 if (!C.isInitialized()) return false;
858 if (C.isAmbiguous()) return true;
863 bool TryToFixBadConversion(unsigned Idx, Sema &S) {
864 bool CanFix = Fix.tryToFixConversion(
865 Conversions[Idx].Bad.FromExpr,
866 Conversions[Idx].Bad.getFromType(),
867 Conversions[Idx].Bad.getToType(), S);
869 // If at least one conversion fails, the candidate cannot be fixed.
876 unsigned getNumParams() const {
878 QualType STy = Surrogate->getConversionType();
879 while (STy->isPointerType() || STy->isReferenceType())
880 STy = STy->getPointeeType();
881 return STy->castAs<FunctionProtoType>()->getNumParams();
884 return Function->getNumParams();
885 return ExplicitCallArguments;
889 friend class OverloadCandidateSet;
891 : IsADLCandidate(CallExpr::NotADL), RewriteKind(CRK_None) {}
894 /// OverloadCandidateSet - A set of overload candidates, used in C++
895 /// overload resolution (C++ 13.3).
896 class OverloadCandidateSet {
898 enum CandidateSetKind {
902 /// C++ [over.match.oper]:
903 /// Lookup of operator function candidates in a call using operator
904 /// syntax. Candidates that have no parameters of class type will be
905 /// skipped unless there is a parameter of (reference to) enum type and
906 /// the corresponding argument is of the same enum type.
909 /// C++ [over.match.copy]:
910 /// Copy-initialization of an object of class type by user-defined
912 CSK_InitByUserDefinedConversion,
914 /// C++ [over.match.ctor], [over.match.list]
915 /// Initialization of an object of class type by constructor,
916 /// using either a parenthesized or braced list of arguments.
917 CSK_InitByConstructor,
920 /// Information about operator rewrites to consider when adding operator
921 /// functions to a candidate set.
922 struct OperatorRewriteInfo {
923 OperatorRewriteInfo()
924 : OriginalOperator(OO_None), AllowRewrittenCandidates(false) {}
925 OperatorRewriteInfo(OverloadedOperatorKind Op, bool AllowRewritten)
926 : OriginalOperator(Op), AllowRewrittenCandidates(AllowRewritten) {}
928 /// The original operator as written in the source.
929 OverloadedOperatorKind OriginalOperator;
930 /// Whether we should include rewritten candidates in the overload set.
931 bool AllowRewrittenCandidates;
933 /// Would use of this function result in a rewrite using a different
935 bool isRewrittenOperator(const FunctionDecl *FD) {
936 return OriginalOperator &&
937 FD->getDeclName().getCXXOverloadedOperator() != OriginalOperator;
940 bool isAcceptableCandidate(const FunctionDecl *FD) {
941 if (!OriginalOperator)
944 // For an overloaded operator, we can have candidates with a different
945 // name in our unqualified lookup set. Make sure we only consider the
946 // ones we're supposed to.
947 OverloadedOperatorKind OO =
948 FD->getDeclName().getCXXOverloadedOperator();
949 return OO && (OO == OriginalOperator ||
950 (AllowRewrittenCandidates &&
951 OO == getRewrittenOverloadedOperator(OriginalOperator)));
954 /// Determine the kind of rewrite that should be performed for this
956 OverloadCandidateRewriteKind
957 getRewriteKind(const FunctionDecl *FD, OverloadCandidateParamOrder PO) {
958 OverloadCandidateRewriteKind CRK = CRK_None;
959 if (isRewrittenOperator(FD))
960 CRK = OverloadCandidateRewriteKind(CRK | CRK_DifferentOperator);
961 if (PO == OverloadCandidateParamOrder::Reversed)
962 CRK = OverloadCandidateRewriteKind(CRK | CRK_Reversed);
966 /// Determine whether we should consider looking for and adding reversed
967 /// candidates for operator Op.
968 bool shouldAddReversed(OverloadedOperatorKind Op);
970 /// Determine whether we should add a rewritten candidate for \p FD with
971 /// reversed parameter order.
972 bool shouldAddReversed(ASTContext &Ctx, const FunctionDecl *FD);
976 SmallVector<OverloadCandidate, 16> Candidates;
977 llvm::SmallPtrSet<uintptr_t, 16> Functions;
979 // Allocator for ConversionSequenceLists. We store the first few of these
980 // inline to avoid allocation for small sets.
981 llvm::BumpPtrAllocator SlabAllocator;
984 CandidateSetKind Kind;
985 OperatorRewriteInfo RewriteInfo;
987 constexpr static unsigned NumInlineBytes =
988 24 * sizeof(ImplicitConversionSequence);
989 unsigned NumInlineBytesUsed = 0;
990 alignas(void *) char InlineSpace[NumInlineBytes];
992 // Address space of the object being constructed.
993 LangAS DestAS = LangAS::Default;
995 /// If we have space, allocates from inline storage. Otherwise, allocates
996 /// from the slab allocator.
997 /// FIXME: It would probably be nice to have a SmallBumpPtrAllocator
999 /// FIXME: Now that this only allocates ImplicitConversionSequences, do we
1000 /// want to un-generalize this?
1001 template <typename T>
1002 T *slabAllocate(unsigned N) {
1003 // It's simpler if this doesn't need to consider alignment.
1004 static_assert(alignof(T) == alignof(void *),
1005 "Only works for pointer-aligned types.");
1006 static_assert(std::is_trivial<T>::value ||
1007 std::is_same<ImplicitConversionSequence, T>::value,
1008 "Add destruction logic to OverloadCandidateSet::clear().");
1010 unsigned NBytes = sizeof(T) * N;
1011 if (NBytes > NumInlineBytes - NumInlineBytesUsed)
1012 return SlabAllocator.Allocate<T>(N);
1013 char *FreeSpaceStart = InlineSpace + NumInlineBytesUsed;
1014 assert(uintptr_t(FreeSpaceStart) % alignof(void *) == 0 &&
1015 "Misaligned storage!");
1017 NumInlineBytesUsed += NBytes;
1018 return reinterpret_cast<T *>(FreeSpaceStart);
1021 void destroyCandidates();
1024 OverloadCandidateSet(SourceLocation Loc, CandidateSetKind CSK,
1025 OperatorRewriteInfo RewriteInfo = {})
1026 : Loc(Loc), Kind(CSK), RewriteInfo(RewriteInfo) {}
1027 OverloadCandidateSet(const OverloadCandidateSet &) = delete;
1028 OverloadCandidateSet &operator=(const OverloadCandidateSet &) = delete;
1029 ~OverloadCandidateSet() { destroyCandidates(); }
1031 SourceLocation getLocation() const { return Loc; }
1032 CandidateSetKind getKind() const { return Kind; }
1033 OperatorRewriteInfo getRewriteInfo() const { return RewriteInfo; }
1035 /// Determine when this overload candidate will be new to the
1037 bool isNewCandidate(Decl *F, OverloadCandidateParamOrder PO =
1038 OverloadCandidateParamOrder::Normal) {
1039 uintptr_t Key = reinterpret_cast<uintptr_t>(F->getCanonicalDecl());
1040 Key |= static_cast<uintptr_t>(PO);
1041 return Functions.insert(Key).second;
1044 /// Exclude a function from being considered by overload resolution.
1045 void exclude(Decl *F) {
1046 isNewCandidate(F, OverloadCandidateParamOrder::Normal);
1047 isNewCandidate(F, OverloadCandidateParamOrder::Reversed);
1050 /// Clear out all of the candidates.
1051 void clear(CandidateSetKind CSK);
1053 using iterator = SmallVectorImpl<OverloadCandidate>::iterator;
1055 iterator begin() { return Candidates.begin(); }
1056 iterator end() { return Candidates.end(); }
1058 size_t size() const { return Candidates.size(); }
1059 bool empty() const { return Candidates.empty(); }
1061 /// Allocate storage for conversion sequences for NumConversions
1063 ConversionSequenceList
1064 allocateConversionSequences(unsigned NumConversions) {
1065 ImplicitConversionSequence *Conversions =
1066 slabAllocate<ImplicitConversionSequence>(NumConversions);
1068 // Construct the new objects.
1069 for (unsigned I = 0; I != NumConversions; ++I)
1070 new (&Conversions[I]) ImplicitConversionSequence();
1072 return ConversionSequenceList(Conversions, NumConversions);
1075 /// Add a new candidate with NumConversions conversion sequence slots
1076 /// to the overload set.
1077 OverloadCandidate &addCandidate(unsigned NumConversions = 0,
1078 ConversionSequenceList Conversions = None) {
1079 assert((Conversions.empty() || Conversions.size() == NumConversions) &&
1080 "preallocated conversion sequence has wrong length");
1082 Candidates.push_back(OverloadCandidate());
1083 OverloadCandidate &C = Candidates.back();
1084 C.Conversions = Conversions.empty()
1085 ? allocateConversionSequences(NumConversions)
1090 /// Find the best viable function on this overload set, if it exists.
1091 OverloadingResult BestViableFunction(Sema &S, SourceLocation Loc,
1092 OverloadCandidateSet::iterator& Best);
1094 SmallVector<OverloadCandidate *, 32> CompleteCandidates(
1095 Sema &S, OverloadCandidateDisplayKind OCD, ArrayRef<Expr *> Args,
1096 SourceLocation OpLoc = SourceLocation(),
1097 llvm::function_ref<bool(OverloadCandidate &)> Filter =
1098 [](OverloadCandidate &) { return true; });
1100 void NoteCandidates(
1101 PartialDiagnosticAt PA, Sema &S, OverloadCandidateDisplayKind OCD,
1102 ArrayRef<Expr *> Args, StringRef Opc = "",
1103 SourceLocation Loc = SourceLocation(),
1104 llvm::function_ref<bool(OverloadCandidate &)> Filter =
1105 [](OverloadCandidate &) { return true; });
1107 void NoteCandidates(Sema &S, ArrayRef<Expr *> Args,
1108 ArrayRef<OverloadCandidate *> Cands,
1110 SourceLocation OpLoc = SourceLocation());
1112 LangAS getDestAS() { return DestAS; }
1114 void setDestAS(LangAS AS) {
1115 assert((Kind == CSK_InitByConstructor ||
1116 Kind == CSK_InitByUserDefinedConversion) &&
1117 "can't set the destination address space when not constructing an "
1124 bool isBetterOverloadCandidate(Sema &S,
1125 const OverloadCandidate &Cand1,
1126 const OverloadCandidate &Cand2,
1128 OverloadCandidateSet::CandidateSetKind Kind);
1130 struct ConstructorInfo {
1131 DeclAccessPair FoundDecl;
1132 CXXConstructorDecl *Constructor;
1133 FunctionTemplateDecl *ConstructorTmpl;
1135 explicit operator bool() const { return Constructor; }
1138 // FIXME: Add an AddOverloadCandidate / AddTemplateOverloadCandidate overload
1139 // that takes one of these.
1140 inline ConstructorInfo getConstructorInfo(NamedDecl *ND) {
1141 if (isa<UsingDecl>(ND))
1142 return ConstructorInfo{};
1144 // For constructors, the access check is performed against the underlying
1145 // declaration, not the found declaration.
1146 auto *D = ND->getUnderlyingDecl();
1147 ConstructorInfo Info = {DeclAccessPair::make(ND, D->getAccess()), nullptr,
1149 Info.ConstructorTmpl = dyn_cast<FunctionTemplateDecl>(D);
1150 if (Info.ConstructorTmpl)
1151 D = Info.ConstructorTmpl->getTemplatedDecl();
1152 Info.Constructor = dyn_cast<CXXConstructorDecl>(D);
1156 } // namespace clang
1158 #endif // LLVM_CLANG_SEMA_OVERLOAD_H