diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c8ef2e8d614a7..0f9728c00e648 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -695,6 +695,10 @@ Bug Fixes to C++ Support
until the noexcept-specifier is instantiated.
- Fix a crash when an implicitly declared ``operator==`` function with a trailing requires-clause has its
constraints compared to that of another declaration.
+- Fix a bug where explicit specializations of member functions/function templates would have substitution
+ performed incorrectly when checking constraints. Fixes (#GH90349).
+- Clang now allows constrained member functions to be explicitly specialized for an implicit instantiation
+ of a class template.
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 9a0bae9c216de..9317ae675c72b 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5437,6 +5437,11 @@ def note_function_template_spec_matched : Note<
def err_function_template_partial_spec : Error<
"function template partial specialization is not allowed">;
+def err_function_member_spec_ambiguous : Error<
+ "ambiguous member function specialization %q0 of %q1">;
+def note_function_member_spec_matched : Note<
+ "member function specialization matches %0">;
+
// C++ Template Instantiation
def err_template_recursion_depth_exceeded : Error<
"recursive template instantiation exceeded maximum depth of %0">,
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index a80ac6dbc7613..ddb3de2b66023 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -9739,6 +9739,9 @@ class Sema final : public SemaBase {
const PartialDiagnostic &CandidateDiag,
bool Complain = true, QualType TargetType = QualType());
+ FunctionDecl *getMoreConstrainedFunction(FunctionDecl *FD1,
+ FunctionDecl *FD2);
+
///@}
//
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index e00c972602829..7bfec4e11f7aa 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -811,7 +811,7 @@ static const Expr *SubstituteConstraintExpressionWithoutSatisfaction(
// this may happen while we're comparing two templates' constraint
// equivalence.
LocalInstantiationScope ScopeForParameters(S);
- if (auto *FD = llvm::dyn_cast<FunctionDecl>(DeclInfo.getDecl()))
+ if (auto *FD = DeclInfo.getDecl()->getAsFunction())
for (auto *PVD : FD->parameters())
ScopeForParameters.InstantiatedLocal(PVD, PVD);
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index a416df2e97c43..f173300b5c96c 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -1303,6 +1303,8 @@ static bool IsOverloadOrOverrideImpl(Sema &SemaRef, FunctionDecl *New,
if (New->isMSVCRTEntryPoint())
return false;
+ NamedDecl *OldDecl = Old;
+ NamedDecl *NewDecl = New;
FunctionTemplateDecl *OldTemplate = Old->getDescribedFunctionTemplate();
FunctionTemplateDecl *NewTemplate = New->getDescribedFunctionTemplate();
@@ -1347,6 +1349,8 @@ static bool IsOverloadOrOverrideImpl(Sema &SemaRef, FunctionDecl *New,
// references to non-instantiated entities during constraint substitution.
// GH78101.
if (NewTemplate) {
+ OldDecl = OldTemplate;
+ NewDecl = NewTemplate;
// C++ [temp.over.link]p4:
// The signature of a function template consists of its function
// signature, its return type and its template parameter list. The names
@@ -1506,13 +1510,14 @@ static bool IsOverloadOrOverrideImpl(Sema &SemaRef, FunctionDecl *New,
}
}
- if (!UseOverrideRules) {
+ if (!UseOverrideRules &&
+ New->getTemplateSpecializationKind() != TSK_ExplicitSpecialization) {
Expr *NewRC = New->getTrailingRequiresClause(),
*OldRC = Old->getTrailingRequiresClause();
if ((NewRC != nullptr) != (OldRC != nullptr))
return true;
-
- if (NewRC && !SemaRef.AreConstraintExpressionsEqual(Old, OldRC, New, NewRC))
+ if (NewRC &&
+ !SemaRef.AreConstraintExpressionsEqual(OldDecl, OldRC, NewDecl, NewRC))
return true;
}
@@ -10695,29 +10700,10 @@ bool clang::isBetterOverloadCandidate(
// -— F1 and F2 are non-template functions with the same
// parameter-type-lists, and F1 is more constrained than F2 [...],
if (!Cand1IsSpecialization && !Cand2IsSpecialization &&
- sameFunctionParameterTypeLists(S, Cand1, Cand2)) {
- FunctionDecl *Function1 = Cand1.Function;
- FunctionDecl *Function2 = Cand2.Function;
- if (FunctionDecl *MF = Function1->getInstantiatedFromMemberFunction())
- Function1 = MF;
- if (FunctionDecl *MF = Function2->getInstantiatedFromMemberFunction())
- Function2 = MF;
-
- const Expr *RC1 = Function1->getTrailingRequiresClause();
- const Expr *RC2 = Function2->getTrailingRequiresClause();
- if (RC1 && RC2) {
- bool AtLeastAsConstrained1, AtLeastAsConstrained2;
- if (S.IsAtLeastAsConstrained(Function1, RC1, Function2, RC2,
- AtLeastAsConstrained1) ||
- S.IsAtLeastAsConstrained(Function2, RC2, Function1, RC1,
- AtLeastAsConstrained2))
- return false;
- if (AtLeastAsConstrained1 != AtLeastAsConstrained2)
- return AtLeastAsConstrained1;
- } else if (RC1 || RC2) {
- return RC1 != nullptr;
- }
- }
+ sameFunctionParameterTypeLists(S, Cand1, Cand2) &&
+ S.getMoreConstrainedFunction(Cand1.Function, Cand2.Function) ==
+ Cand1.Function)
+ return true;
// -- F1 is a constructor for a class D, F2 is a constructor for a base
// class B of D, and for all arguments the corresponding parameters of
@@ -13385,25 +13371,6 @@ Sema::resolveAddressOfSingleOverloadCandidate(Expr *E, DeclAccessPair &Pair) {
static_cast<int>(CUDA().IdentifyPreference(Caller, FD2));
};
- auto CheckMoreConstrained = [&](FunctionDecl *FD1,
- FunctionDecl *FD2) -> std::optional<bool> {
- if (FunctionDecl *MF = FD1->getInstantiatedFromMemberFunction())
- FD1 = MF;
- if (FunctionDecl *MF = FD2->getInstantiatedFromMemberFunction())
- FD2 = MF;
- SmallVector<const Expr *, 1> AC1, AC2;
- FD1->getAssociatedConstraints(AC1);
- FD2->getAssociatedConstraints(AC2);
- bool AtLeastAsConstrained1, AtLeastAsConstrained2;
- if (IsAtLeastAsConstrained(FD1, AC1, FD2, AC2, AtLeastAsConstrained1))
- return std::nullopt;
- if (IsAtLeastAsConstrained(FD2, AC2, FD1, AC1, AtLeastAsConstrained2))
- return std::nullopt;
- if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
- return std::nullopt;
- return AtLeastAsConstrained1;
- };
-
// Don't use the AddressOfResolver because we're specifically looking for
// cases where we have one overload candidate that lacks
// enable_if/pass_object_size/...
@@ -13440,15 +13407,14 @@ Sema::resolveAddressOfSingleOverloadCandidate(Expr *E, DeclAccessPair &Pair) {
}
// FD has the same CUDA prefernece than Result. Continue check
// constraints.
- std::optional<bool> MoreConstrainedThanPrevious =
- CheckMoreConstrained(FD, Result);
- if (!MoreConstrainedThanPrevious) {
- IsResultAmbiguous = true;
- AmbiguousDecls.push_back(FD);
+ FunctionDecl *MoreConstrained = getMoreConstrainedFunction(FD, Result);
+ if (MoreConstrained != FD) {
+ if (!MoreConstrained) {
+ IsResultAmbiguous = true;
+ AmbiguousDecls.push_back(FD);
+ }
continue;
}
- if (!*MoreConstrainedThanPrevious)
- continue;
// FD is more constrained - replace Result with it.
}
FoundBetter();
@@ -13467,7 +13433,7 @@ Sema::resolveAddressOfSingleOverloadCandidate(Expr *E, DeclAccessPair &Pair) {
// constraints.
if (getLangOpts().CUDA && CheckCUDAPreference(Skipped, Result) != 0)
continue;
- if (!CheckMoreConstrained(Skipped, Result))
+ if (!getMoreConstrainedFunction(Skipped, Result))
return nullptr;
}
Pair = DAP;
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 5c72270ff1504..7e57fa0696725 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -10339,24 +10339,53 @@ Sema::CheckMemberSpecialization(NamedDecl *Member, LookupResult &Previous) {
if (Previous.empty()) {
// Nowhere to look anyway.
} else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(Member)) {
+ SmallVector<FunctionDecl *> Candidates;
+ bool Ambiguous = false;
for (LookupResult::iterator I = Previous.begin(), E = Previous.end();
I != E; ++I) {
- NamedDecl *D = (*I)->getUnderlyingDecl();
- if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(D)) {
- QualType Adjusted = Function->getType();
- if (!hasExplicitCallingConv(Adjusted))
- Adjusted = adjustCCAndNoReturn(Adjusted, Method->getType());
- // This doesn't handle deduced return types, but both function
- // declarations should be undeduced at this point.
- if (Context.hasSameType(Adjusted, Method->getType())) {
- FoundInstantiation = *I;
- Instantiation = Method;
- InstantiatedFrom = Method->getInstantiatedFromMemberFunction();
- MSInfo = Method->getMemberSpecializationInfo();
- break;
- }
+ CXXMethodDecl *Method =
+ dyn_cast<CXXMethodDecl>((*I)->getUnderlyingDecl());
+ if (!Method)
+ continue;
+ QualType Adjusted = Function->getType();
+ if (!hasExplicitCallingConv(Adjusted))
+ Adjusted = adjustCCAndNoReturn(Adjusted, Method->getType());
+ // This doesn't handle deduced return types, but both function
+ // declarations should be undeduced at this point.
+ if (!Context.hasSameType(Adjusted, Method->getType()))
+ continue;
+ if (ConstraintSatisfaction Satisfaction;
+ Method->getTrailingRequiresClause() &&
+ (CheckFunctionConstraints(Method, Satisfaction,
+ /*UsageLoc=*/Member->getLocation(),
+ /*ForOverloadResolution=*/true) ||
+ !Satisfaction.IsSatisfied))
+ continue;
+ Candidates.push_back(Method);
+ FunctionDecl *MoreConstrained =
+ Instantiation ? getMoreConstrainedFunction(
+ Method, cast<FunctionDecl>(Instantiation))
+ : Method;
+ if (!MoreConstrained) {
+ Ambiguous = true;
+ continue;
+ }
+ if (MoreConstrained == Method) {
+ Ambiguous = false;
+ FoundInstantiation = *I;
+ Instantiation = Method;
+ InstantiatedFrom = Method->getInstantiatedFromMemberFunction();
+ MSInfo = Method->getMemberSpecializationInfo();
}
}
+ if (Ambiguous) {
+ Diag(Member->getLocation(), diag::err_function_member_spec_ambiguous)
+ << Member << (InstantiatedFrom ? InstantiatedFrom : Instantiation);
+ for (FunctionDecl *Candidate : Candidates)
+ Diag(Candidate->getLocation(), diag::note_function_member_spec_matched)
+ << Candidate;
+ return true;
+ }
} else if (isa<VarDecl>(Member)) {
VarDecl *PrevVar;
if (Previous.isSingleResult() &&
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index dcaea4a77bffd..fe7e35d841510 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -5852,6 +5852,38 @@ UnresolvedSetIterator Sema::getMostSpecialized(
return SpecEnd;
}
+/// Returns the more constrained function according to the rules of
+/// partial ordering by constraints (C++ [temp.constr.order]).
+///
+/// \param FD1 the first function
+///
+/// \param FD2 the second function
+///
+/// \returns the more constrained function. If neither function is
+/// more constrained, returns NULL.
+FunctionDecl *Sema::getMoreConstrainedFunction(FunctionDecl *FD1,
+ FunctionDecl *FD2) {
+ assert(!FD1->getDescribedTemplate() && !FD2->getDescribedTemplate() &&
+ "not for function templates");
+ FunctionDecl *F1 = FD1;
+ if (FunctionDecl *MF = FD1->getInstantiatedFromMemberFunction())
+ F1 = MF;
+ FunctionDecl *F2 = FD2;
+ if (FunctionDecl *MF = FD2->getInstantiatedFromMemberFunction())
+ F2 = MF;
+ llvm::SmallVector<const Expr *, 1> AC1, AC2;
+ F1->getAssociatedConstraints(AC1);
+ F2->getAssociatedConstraints(AC2);
+ bool AtLeastAsConstrained1, AtLeastAsConstrained2;
+ if (IsAtLeastAsConstrained(F1, AC1, F2, AC2, AtLeastAsConstrained1))
+ return nullptr;
+ if (IsAtLeastAsConstrained(F2, AC2, F1, AC1, AtLeastAsConstrained2))
+ return nullptr;
+ if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
+ return nullptr;
+ return AtLeastAsConstrained1 ? FD1 : FD2;
+}
+
/// Determine whether one partial specialization, P1, is at least as
/// specialized than another, P2.
///
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 3a9fd906b7af8..07626058c7977 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -275,6 +275,13 @@ Response HandleFunction(Sema &SemaRef, const FunctionDecl *Function,
TemplateArgs->asArray(),
/*Final=*/false);
+ if (RelativeToPrimary &&
+ (Function->getTemplateSpecializationKind() ==
+ TSK_ExplicitSpecialization ||
+ (Function->getFriendObjectKind() &&
+ !Function->getPrimaryTemplate()->getFriendObjectKind())))
+ return Response::UseNextDecl(Function);
+
// If this function was instantiated from a specialized member that is
// a function template, we're done.
assert(Function->getPrimaryTemplate() && "No function template?");
diff --git a/clang/test/CXX/temp/temp.spec/temp.expl.spec/p14-23.cpp b/clang/test/CXX/temp/temp.spec/temp.expl.spec/p14-23.cpp
new file mode 100644
index 0000000000000..dc17cea99d435
--- /dev/null
+++ b/clang/test/CXX/temp/temp.spec/temp.expl.spec/p14-23.cpp
@@ -0,0 +1,60 @@
+// RUN: %clang_cc1 -std=c++20 -verify %s
+
+template<int I>
+concept C = I >= 4;
+
+template<int I>
+concept D = I < 8;
+
+template<int I>
+struct A {
+ constexpr static int f() { return 0; }
+ constexpr static int f() requires C<I> && D<I> { return 1; }
+ constexpr static int f() requires C<I> { return 2; }
+
+ constexpr static int g() requires C<I> { return 0; } // #candidate-0
+ constexpr static int g() requires D<I> { return 1; } // #candidate-1
+
+ constexpr static int h() requires C<I> { return 0; } // expected-note {{member declaration nearly matches}}
+};
+
+template<>
+constexpr int A<2>::f() { return 3; }
+
+template<>
+constexpr int A<4>::f() { return 4; }
+
+template<>
+constexpr int A<8>::f() { return 5; }
+
+static_assert(A<3>::f() == 0);
+static_assert(A<5>::f() == 1);
+static_assert(A<9>::f() == 2);
+static_assert(A<2>::f() == 3);
+static_assert(A<4>::f() == 4);
+static_assert(A<8>::f() == 5);
+
+template<>
+constexpr int A<0>::g() { return 2; }
+
+template<>
+constexpr int A<8>::g() { return 3; }
+
+template<>
+constexpr int A<6>::g() { return 4; } // expected-error {{ambiguous member function specialization 'A<6>::g' of 'A::g'}}
+ // expected-note@#candidate-0 {{member function specialization matches 'g'}}
+ // expected-note@#candidate-1 {{member function specialization matches 'g'}}
+
+static_assert(A<9>::g() == 0);
+static_assert(A<1>::g() == 1);
+static_assert(A<0>::g() == 2);
+static_assert(A<8>::g() == 3);
+
+template<>
+constexpr int A<4>::h() { return 1; }
+
+template<>
+constexpr int A<0>::h() { return 2; } // expected-error {{out-of-line definition of 'h' does not match any declaration in 'A<0>'}}
+
+static_assert(A<5>::h() == 0);
+static_assert(A<4>::h() == 1);
diff --git a/clang/test/CXX/temp/temp.spec/temp.expl.spec/p8.cpp b/clang/test/CXX/temp/temp.spec/temp.expl.spec/p8.cpp
new file mode 100644
index 0000000000000..87e10d10e4b45
--- /dev/null
+++ b/clang/test/CXX/temp/temp.spec/temp.expl.spec/p8.cpp
@@ -0,0 +1,74 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+template<typename T>
+concept C = sizeof(T) <= sizeof(long);
+
+template<typename T>
+struct A {
+ template<typename U>
+ void f(U) requires C<U>;
+
+ void g() requires C<T>;
+
+ template<typename U>
+ void h(U) requires C<T>;
+
+ constexpr int i() requires C<T> {
+ return 0;
+ }
+
+ constexpr int i() requires C<T> && true {
+ return 1;
+ }
+
+ template<>
+ void f(char);
+};
+
+template<>
+template<typename U>
+void A<short>::f(U) requires C<U>;
+
+template<>
+template<typename U>
+void A<short>::h(U) requires C<short>;
+
+template<>
+template<>
+void A<int>::f(int);
+
+template<>
+void A<long>::g();
+
+template<>
+constexpr int A<long>::i() {
+ return 2;
+}
+
+static_assert(A<long>().i() == 2);
+
+template<typename T>
+struct D {
+ template<typename U>
+ static constexpr int f(U);
+
+ template<typename U>
+ static constexpr int f(U) requires (sizeof(T) == 1);
+
+ template<>
+ constexpr int f(int) {
+ return 1;
+ }
+};
+
+template<>
+template<typename U>
+constexpr int D<signed char>::f(U) requires (sizeof(signed char) == 1) {
+ return 0;
+}
+
+static_assert(D<char>::f(0) == 1);
+static_assert(D<char[2]>::f(0) == 1);
+static_assert(D<signed char>::f(0) == 1);
+static_assert(D<signed char>::f(0.0) == 0);