[clang][Sema] Bugfix for choosing the more specialized overload #83279
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@llvm/pr-subscribers-clang Author: Botond István Horváth (HoBoIs) ChangesThere was a bug in clang where it couldn't choose which overload candidate is more specialized if it was comparing a member-function to a non-member function. Previously, this was detected as an ambigouity, now clang chooses correctly. This patch fixes the bug by fully implementing CWG2445 and moving the template transformation described in [temp.func.order] paragraph 3 from isAtLeastAsSpecializedAs to Sema::getMoreSpecializedTemplate so we have the transformed parameter list during the whole comperrassion. Also, to be able to add the correct type for the implicit object parameter Sema::getMoreSpecializedTemplate has new parameters for the object type. Fixes #74494 and #82509 Full diff: https://github.com/llvm/llvm-project/pull/83279.diff 3 Files Affected:
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index ef4b93fac95ce5..1a2a3a6bebd95e 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -9463,7 +9463,9 @@ class Sema final {
FunctionTemplateDecl *getMoreSpecializedTemplate(
FunctionTemplateDecl *FT1, FunctionTemplateDecl *FT2, SourceLocation Loc,
TemplatePartialOrderingContext TPOC, unsigned NumCallArguments1,
- unsigned NumCallArguments2, bool Reversed = false);
+ unsigned NumCallArguments2, QualType ObjType1 = {},
+ QualType ObjType2 = {}, bool Reversed = false);
+
UnresolvedSetIterator
getMostSpecialized(UnresolvedSetIterator SBegin, UnresolvedSetIterator SEnd,
TemplateSpecCandidateSet &FailedCandidates,
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 7d38043890ca20..60138236abf1d8 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -10526,14 +10526,24 @@ bool clang::isBetterOverloadCandidate(
// according to the partial ordering rules described in 14.5.5.2, or,
// if not that,
if (Cand1IsSpecialization && Cand2IsSpecialization) {
+ const auto *ObjContext1 =
+ dyn_cast<CXXRecordDecl>(Cand1.FoundDecl->getDeclContext());
+ const auto *ObjContext2 =
+ dyn_cast<CXXRecordDecl>(Cand2.FoundDecl->getDeclContext());
if (FunctionTemplateDecl *BetterTemplate = S.getMoreSpecializedTemplate(
Cand1.Function->getPrimaryTemplate(),
Cand2.Function->getPrimaryTemplate(), Loc,
isa<CXXConversionDecl>(Cand1.Function) ? TPOC_Conversion
: TPOC_Call,
Cand1.ExplicitCallArguments, Cand2.ExplicitCallArguments,
- Cand1.isReversed() ^ Cand2.isReversed()))
+ ObjContext1 ? QualType(ObjContext1->getTypeForDecl(), 0)
+ : QualType{},
+ ObjContext2 ? QualType(ObjContext2->getTypeForDecl(), 0)
+ : QualType{},
+ Cand1.isReversed() ^ Cand2.isReversed())) {
return BetterTemplate == Cand1.Function->getPrimaryTemplate();
+ }
+
}
// -— F1 and F2 are non-template functions with the same
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 563491f76f5478..2af3c29ae1f1c4 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -5333,11 +5333,31 @@ bool Sema::CheckIfFunctionSpecializationIsImmediate(FunctionDecl *FD,
return false;
}
+static QualType GetImplicitObjectParameterTypeCXX20(ASTContext &Context,
+ const CXXMethodDecl *Method,
+ QualType rawType,
+ bool isOtherRvr) {
+ // C++20 [temp.func.order]p3.1, p3.2:
+ //- The type X(M ) is “rvalue reference to cv A” if the optional ref-qualifier
+ // of M is && or if M has no ref-qualifier and the positionally-corresponding
+ // parameter of the other transformed template has rvalue reference type;
+ // if this determination depends recursively upon whether X(M ) is an rvalue
+ // reference type, it is not considered to have rvalue reference type.
+ //- Otherwise, X(M ) is “lvalue reference to cv A”.
+ assert(Method && !Method->isExplicitObjectMemberFunction() &&
+ "expected a member function with no explicit object parameter");
+
+ rawType = Context.getQualifiedType(rawType, Method->getMethodQualifiers());
+ if (Method->getRefQualifier() == RQ_RValue ||
+ (isOtherRvr && Method->getRefQualifier() == RQ_None))
+ return Context.getRValueReferenceType(rawType);
+ return Context.getLValueReferenceType(rawType);
+}
+
/// If this is a non-static member function,
-static void
-AddImplicitObjectParameterType(ASTContext &Context,
- CXXMethodDecl *Method,
- SmallVectorImpl<QualType> &ArgTypes) {
+static QualType GetImplicitObjectParameterType(ASTContext &Context,
+ const CXXMethodDecl *Method,
+ QualType rawType) {
// C++11 [temp.func.order]p3:
// [...] The new parameter is of type "reference to cv A," where cv are
// the cv-qualifiers of the function template (if any) and A is
@@ -5347,24 +5367,21 @@ AddImplicitObjectParameterType(ASTContext &Context,
// reference type based on [over.match.funcs]p4.
assert(Method && Method->isImplicitObjectMemberFunction() &&
"expected an implicit objet function");
- QualType ArgTy = Context.getTypeDeclType(Method->getParent());
- ArgTy = Context.getQualifiedType(ArgTy, Method->getMethodQualifiers());
+ rawType = Context.getQualifiedType(rawType, Method->getMethodQualifiers());
if (Method->getRefQualifier() == RQ_RValue)
- ArgTy = Context.getRValueReferenceType(ArgTy);
- else
- ArgTy = Context.getLValueReferenceType(ArgTy);
- ArgTypes.push_back(ArgTy);
+ return Context.getRValueReferenceType(rawType);
+ return Context.getLValueReferenceType(rawType);
}
/// Determine whether the function template \p FT1 is at least as
/// specialized as \p FT2.
-static bool isAtLeastAsSpecializedAs(Sema &S,
- SourceLocation Loc,
- FunctionTemplateDecl *FT1,
- FunctionTemplateDecl *FT2,
+static bool isAtLeastAsSpecializedAs(Sema &S, SourceLocation Loc,
+ const FunctionTemplateDecl *FT1,
+ const FunctionTemplateDecl *FT2,
TemplatePartialOrderingContext TPOC,
- unsigned NumCallArguments1,
- bool Reversed) {
+ bool Reversed,
+ const SmallVector<QualType, 4> &Args1,
+ const SmallVector<QualType, 4> &Args2) {
assert(!Reversed || TPOC == TPOC_Call);
FunctionDecl *FD1 = FT1->getTemplatedDecl();
@@ -5381,66 +5398,8 @@ static bool isAtLeastAsSpecializedAs(Sema &S,
// The types used to determine the ordering depend on the context in which
// the partial ordering is done:
TemplateDeductionInfo Info(Loc);
- SmallVector<QualType, 4> Args2;
switch (TPOC) {
- case TPOC_Call: {
- // - In the context of a function call, the function parameter types are
- // used.
- CXXMethodDecl *Method1 = dyn_cast<CXXMethodDecl>(FD1);
- CXXMethodDecl *Method2 = dyn_cast<CXXMethodDecl>(FD2);
-
- // C++11 [temp.func.order]p3:
- // [...] If only one of the function templates is a non-static
- // member, that function template is considered to have a new
- // first parameter inserted in its function parameter list. The
- // new parameter is of type "reference to cv A," where cv are
- // the cv-qualifiers of the function template (if any) and A is
- // the class of which the function template is a member.
- //
- // Note that we interpret this to mean "if one of the function
- // templates is a non-static member and the other is a non-member";
- // otherwise, the ordering rules for static functions against non-static
- // functions don't make any sense.
- //
- // C++98/03 doesn't have this provision but we've extended DR532 to cover
- // it as wording was broken prior to it.
- SmallVector<QualType, 4> Args1;
-
- unsigned NumComparedArguments = NumCallArguments1;
-
- if (!Method2 && Method1 && Method1->isImplicitObjectMemberFunction()) {
- // Compare 'this' from Method1 against first parameter from Method2.
- AddImplicitObjectParameterType(S.Context, Method1, Args1);
- ++NumComparedArguments;
- } else if (!Method1 && Method2 &&
- Method2->isImplicitObjectMemberFunction()) {
- // Compare 'this' from Method2 against first parameter from Method1.
- AddImplicitObjectParameterType(S.Context, Method2, Args2);
- } else if (Method1 && Method2 && Reversed &&
- Method1->isImplicitObjectMemberFunction() &&
- Method2->isImplicitObjectMemberFunction()) {
- // Compare 'this' from Method1 against second parameter from Method2
- // and 'this' from Method2 against second parameter from Method1.
- AddImplicitObjectParameterType(S.Context, Method1, Args1);
- AddImplicitObjectParameterType(S.Context, Method2, Args2);
- ++NumComparedArguments;
- }
-
- Args1.insert(Args1.end(), Proto1->param_type_begin(),
- Proto1->param_type_end());
- Args2.insert(Args2.end(), Proto2->param_type_begin(),
- Proto2->param_type_end());
-
- // C++ [temp.func.order]p5:
- // The presence of unused ellipsis and default arguments has no effect on
- // the partial ordering of function templates.
- if (Args1.size() > NumComparedArguments)
- Args1.resize(NumComparedArguments);
- if (Args2.size() > NumComparedArguments)
- Args2.resize(NumComparedArguments);
- if (Reversed)
- std::reverse(Args2.begin(), Args2.end());
-
+ case TPOC_Call:
if (DeduceTemplateArguments(S, TemplateParams, Args2.data(), Args2.size(),
Args1.data(), Args1.size(), Info, Deduced,
TDF_None, /*PartialOrdering=*/true) !=
@@ -5448,7 +5407,6 @@ static bool isAtLeastAsSpecializedAs(Sema &S,
return false;
break;
- }
case TPOC_Conversion:
// - In the context of a call to a conversion operator, the return types
@@ -5539,6 +5497,14 @@ static bool isAtLeastAsSpecializedAs(Sema &S,
/// \param NumCallArguments2 The number of arguments in the call to FT2, used
/// only when \c TPOC is \c TPOC_Call.
///
+/// \param RawObjType1 The type of the object parameter of FT1 if a member
+/// function only used if \c TPOC is \c TPOC_Call and FT1 is a Function
+/// template from a member function
+///
+/// \param RawObjType2 The type of the object parameter of FT2 if a member
+/// function only used if \c TPOC is \c TPOC_Call and FT2 is a Function
+/// template from a member function
+///
/// \param Reversed If \c true, exactly one of FT1 and FT2 is an overload
/// candidate with a reversed parameter order. In this case, the corresponding
/// P/A pairs between FT1 and FT2 are reversed.
@@ -5548,13 +5514,113 @@ static bool isAtLeastAsSpecializedAs(Sema &S,
FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
FunctionTemplateDecl *FT1, FunctionTemplateDecl *FT2, SourceLocation Loc,
TemplatePartialOrderingContext TPOC, unsigned NumCallArguments1,
- unsigned NumCallArguments2, bool Reversed) {
+ unsigned NumCallArguments2, QualType RawObjType1, QualType RawObjType2,
+ bool Reversed) {
+ SmallVector<QualType, 4> Args1;
+ SmallVector<QualType, 4> Args2;
+ const FunctionDecl *FD1 = FT1->getTemplatedDecl();
+ const FunctionDecl *FD2 = FT2->getTemplatedDecl();
+ bool shouldConvert1 = false;
+ bool shouldConvert2 = false;
+ QualType ObjType1;
+ QualType ObjType2;
+ if (TPOC == TPOC_Call) {
+ const FunctionProtoType *Proto1 =
+ FD1->getType()->getAs<FunctionProtoType>();
+ const FunctionProtoType *Proto2 =
+ FD2->getType()->getAs<FunctionProtoType>();
- bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
- NumCallArguments1, Reversed);
- bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
- NumCallArguments2, Reversed);
+ // - In the context of a function call, the function parameter types are
+ // used.
+ const CXXMethodDecl *Method1 = dyn_cast<CXXMethodDecl>(FD1);
+ const CXXMethodDecl *Method2 = dyn_cast<CXXMethodDecl>(FD2);
+
+ if (getLangOpts().CPlusPlus20) {
+ // C++20 [temp.func.order]p3
+ // [...] Each function template M that is a member function is
+ // considered to have a new first parameter of type
+ // X(M), described below, inserted in its function parameter list.
+ //
+ // Note that we interpret "that is a member function" as
+ // "that is a member function with no expicit object argument".
+ // Otherwise the ordering rules for methods with expicit objet arguments
+ // against anything else make no sense.
+ shouldConvert1 = Method1 && !Method1->isExplicitObjectMemberFunction();
+ shouldConvert2 = Method2 && !Method2->isExplicitObjectMemberFunction();
+ if (shouldConvert1) {
+ bool isR2 =
+ Method2 && !Method2->isExplicitObjectMemberFunction()
+ ? Method2->getRefQualifier() == RQ_RValue
+ : Proto2->param_type_begin()[0]->isRValueReferenceType();
+ // Compare 'this' from Method1 against first parameter from Method2.
+ ObjType1 = GetImplicitObjectParameterTypeCXX20(this->Context, Method1,
+ RawObjType1, isR2);
+ Args1.push_back(ObjType1);
+ }
+ if (shouldConvert2) {
+ bool isR1 =
+ Method1 && !Method1->isExplicitObjectMemberFunction()
+ ? Method1->getRefQualifier() == RQ_RValue
+ : Proto1->param_type_begin()[0]->isRValueReferenceType();
+ // Compare 'this' from Method2 against first parameter from Method1.
+ ObjType2 = GetImplicitObjectParameterTypeCXX20(this->Context, Method2,
+ RawObjType2, isR1);
+ Args2.push_back(ObjType2);
+ }
+ } else {
+ // C++11 [temp.func.order]p3:
+ // [...] If only one of the function templates is a non-static
+ // member, that function template is considered to have a new
+ // first parameter inserted in its function parameter list. The
+ // new parameter is of type "reference to cv A," where cv are
+ // the cv-qualifiers of the function template (if any) and A is
+ // the class of which the function template is a member.
+ //
+ // Note that we interpret this to mean "if one of the function
+ // templates is a non-static member and the other is a non-member";
+ // otherwise, the ordering rules for static functions against non-static
+ // functions don't make any sense.
+ //
+ // C++98/03 doesn't have this provision but we've extended DR532 to cover
+ // it as wording was broken prior to it.
+ shouldConvert1 =
+ !Method2 && Method1 && Method1->isImplicitObjectMemberFunction();
+ shouldConvert2 =
+ !Method1 && Method2 && Method2->isImplicitObjectMemberFunction();
+ if (shouldConvert1) {
+ // Compare 'this' from Method1 against first parameter from Method2.
+ ObjType1 =
+ GetImplicitObjectParameterType(this->Context, Method1, RawObjType1);
+ Args1.push_back(ObjType1);
+ }
+ if (shouldConvert2) {
+ // Compare 'this' from Method2 against first parameter from Method1.
+ ObjType2 =
+ GetImplicitObjectParameterType(this->Context, Method2, RawObjType2);
+ Args2.push_back(ObjType2);
+ }
+ }
+ unsigned NumComparedArguments = NumCallArguments1 + shouldConvert1;
+
+ Args1.insert(Args1.end(), Proto1->param_type_begin(),
+ Proto1->param_type_end());
+ Args2.insert(Args2.end(), Proto2->param_type_begin(),
+ Proto2->param_type_end());
+ // C++ [temp.func.order]p5:
+ // The presence of unused ellipsis and default arguments has no effect on
+ // the partial ordering of function templates.
+ if (Args1.size() > NumComparedArguments)
+ Args1.resize(NumComparedArguments);
+ if (Args2.size() > NumComparedArguments)
+ Args2.resize(NumComparedArguments);
+ if (Reversed)
+ std::reverse(Args2.begin(), Args2.end());
+ }
+ bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC, Reversed,
+ Args1, Args2);
+ bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC, Reversed,
+ Args2, Args1);
// C++ [temp.deduct.partial]p10:
// F is more specialized than G if F is at least as specialized as G and G
// is not at least as specialized as F.
@@ -5568,12 +5634,28 @@ FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
// ... and if G has a trailing function parameter pack for which F does not
// have a corresponding parameter, and if F does not have a trailing
// function parameter pack, then F is more specialized than G.
- FunctionDecl *FD1 = FT1->getTemplatedDecl();
- FunctionDecl *FD2 = FT2->getTemplatedDecl();
- unsigned NumParams1 = FD1->getNumParams();
- unsigned NumParams2 = FD2->getNumParams();
- bool Variadic1 = NumParams1 && FD1->parameters().back()->isParameterPack();
- bool Variadic2 = NumParams2 && FD2->parameters().back()->isParameterPack();
+
+ SmallVector<QualType> param1;
+ param1.reserve(FD1->param_size() + shouldConvert1);
+ if (shouldConvert1)
+ param1.push_back(ObjType1);
+ for (const auto &x : FD1->parameters())
+ param1.push_back(x->getType());
+
+ SmallVector<QualType> param2;
+ param2.reserve(FD2->param_size() + shouldConvert2);
+ if (shouldConvert2)
+ param2.push_back(ObjType2);
+ for (const auto &x : FD2->parameters())
+ param2.push_back(x->getType());
+
+ unsigned NumParams1 = param1.size();
+ unsigned NumParams2 = param2.size();
+
+ bool Variadic1 =
+ FD1->param_size() && FD1->parameters().back()->isParameterPack();
+ bool Variadic2 =
+ FD2->param_size() && FD2->parameters().back()->isParameterPack();
if (Variadic1 != Variadic2) {
if (Variadic1 && NumParams1 > NumParams2)
return FT2;
@@ -5584,8 +5666,8 @@ FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
// This a speculative fix for CWG1432 (Similar to the fix for CWG1395) that
// there is no wording or even resolution for this issue.
for (int i = 0, e = std::min(NumParams1, NumParams2); i < e; ++i) {
- QualType T1 = FD1->getParamDecl(i)->getType().getCanonicalType();
- QualType T2 = FD2->getParamDecl(i)->getType().getCanonicalType();
+ QualType T1 = param1[i].getCanonicalType();
+ QualType T2 = param2[i].getCanonicalType();
auto *TST1 = dyn_cast<TemplateSpecializationType>(T1);
auto *TST2 = dyn_cast<TemplateSpecializationType>(T2);
if (!TST1 || !TST2)
@@ -5644,8 +5726,7 @@ FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
// Any top-level cv-qualifiers modifying a parameter type are deleted when
// forming the function type.
for (unsigned i = 0; i < NumParams1; ++i)
- if (!Context.hasSameUnqualifiedType(FD1->getParamDecl(i)->getType(),
- FD2->getParamDecl(i)->getType()))
+ if (!Context.hasSameUnqualifiedType(param1[i], param2[i]))
return nullptr;
// C++20 [temp.func.order]p6.3:
|
|
@zygoloid @erichkeane Could you take a look? |
|
✅ With the latest revision this PR passed the C/C++ code formatter. |
erichkeane
reviewed
Feb 28, 2024
erichkeane
reviewed
Feb 28, 2024
Endilll
requested changes
Mar 1, 2024
Endilll
approved these changes
Mar 1, 2024
I have added tests to other files what are relevant for the DR too. Should I move them here? |
I trust your judgement here. Your PR touches a topic complicated enough that I don't feel qualified to make the judgement myself. My stance is that DRs should be considered narrow in scope. So if you think that your additional tests are directly related to what the DR is about, go ahead. For instance, when DR is about cv-qualifiers in variable declarations, but the provided examples only cover In my view, DR test suite prioritizes being on spot more than just containing sheer volume of tests. |
|
I have added tests for rvalref-s and |
|
@erichkeane a question: this PR is partly a fix for a DR for c++20. Right now I only apply the fix for C++20 and newer. Is there a reason for not applying this fix for older standards? I don't see how it would break any existing code, and making the fix retroactive doesn't make any test fail. |
I don't think checking for c++20 is useful because rewritten candidates are a c++20- feature anyway |
Yes, but the resolution of the DR also talks about the reference type of the object parameter. (If I apply the patch retroactively the code will get simpler.) |
|
Yeah, agree with @cor3ntin here. I don't think this needs the C++20 check. Additionally, DRs are usually backported as far as they are 'useful' when possible, so any checks in a DR are a bit of a 'smell' anyway. |
|
@erichkeane Thank you for the suggestions, I have removed the checking for C++20 and I also changed to the |
erichkeane
approved these changes
Mar 5, 2024
There was a problem hiding this comment.
Only some minor things left, so approving. Mostly, for the 'type' and 'context', just do them the way they would read:
So "Object One Type" (plus we use Ty to mean type). Same with Context.
Finally, SmallVector doesn't need a size set, so just using the 'default' value (which it calculates for you!) is sufficient here.
Feel free to merge when CI agrees with you on the above/below changes.
There was a bug in clang where it couldn't choose which overload candidate is more specialized if it was comparing a member-function to a non-member function. Previously, this was detected as an ambigouity, now clang chooses correctly. This patch fixes the bug by fully implementing CWG2445 and moving the template transformation described in [temp.func.order] paragraph 3 from isAtLeastAsSpecializedAs to Sema::getMoreSpecializedTemplate so we have the transformed parameter list during the whole comperrassion. Also, to be able to add the correct type for the implicit object parameter Sema::getMoreSpecializedTemplate has new parameters for the object type.
whisperity
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Mar 11, 2024
…#83279) There was a bug in Clang where it couldn't choose which overload candidate was more specialized if it was comparing a member-function to a non-member function. Previously, this was detected as an ambiguity, now Clang chooses correctly. This patch fixes the bug by fully implementing CWG2445 and moving the template transformation described in `[temp.func.order]` paragraph 3 from `isAtLeastAsSpecializedAs()` to `Sema::getMoreSpecializedTemplate()` so we have the transformed parameter list during the whole comparison. Also, to be able to add the correct type for the implicit object parameter `Sema::getMoreSpecializedTemplate()` has new parameters for the object type. Fixes llvm#74494, fixes llvm#82509
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There was a bug in Clang where it couldn't choose which overload candidate was more specialized if it was comparing a member-function to a non-member function. Previously, this was detected as an ambiguity, now Clang chooses correctly.
This patch fixes the bug by fully implementing CWG2445 and moving the template transformation described in
[temp.func.order]paragraph 3 fromisAtLeastAsSpecializedAs()toSema::getMoreSpecializedTemplate()so we have the transformed parameter list during the whole comparison. Also, to be able to add the correct type for the implicit object parameterSema::getMoreSpecializedTemplate()has new parameters for the object type.Fixes #74494, fixes #82509