[clang] [clang] Bugfix for choosing the more specialized overload (PR #83279)
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Wed Feb 28 07:43:27 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Botond István Horváth (HoBoIs)
<details>
<summary>Changes</summary>
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.
Fixes #<!-- -->74494 and #<!-- -->82509
---
Full diff: https://github.com/llvm/llvm-project/pull/83279.diff
3 Files Affected:
- (modified) clang/include/clang/Sema/Sema.h (+3-1)
- (modified) clang/lib/Sema/SemaOverload.cpp (+11-1)
- (modified) clang/lib/Sema/SemaTemplateDeduction.cpp (+172-91)
``````````diff
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:
``````````
</details>
https://github.com/llvm/llvm-project/pull/83279
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