https://github.com/philnik777 updated
https://github.com/llvm/llvm-project/pull/99473
>From d6903daf0da6979822b8981ea3641455ff6d06f8 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklau...@berlin.de>
Date: Tue, 16 Jul 2024 14:48:10 +0200
Subject: [PATCH 1/4] [Clang] Add __common_type builtin
---
clang/include/clang/AST/ASTContext.h | 11 ++
clang/include/clang/AST/DeclID.h | 5 +-
clang/include/clang/Basic/Builtins.h | 5 +-
clang/include/clang/Sema/Sema.h | 4 +
clang/lib/AST/ASTContext.cpp | 7 +
clang/lib/AST/ASTImporter.cpp | 3 +
clang/lib/AST/DeclTemplate.cpp | 53 ++++++
clang/lib/Lex/PPMacroExpansion.cpp | 1 +
clang/lib/Sema/SemaChecking.cpp | 8 +
clang/lib/Sema/SemaLookup.cpp | 4 +
clang/lib/Sema/SemaTemplate.cpp | 160 +++++++++++++++++-
clang/lib/Serialization/ASTReader.cpp | 3 +
clang/lib/Serialization/ASTWriter.cpp | 2 +
clang/test/SemaCXX/type-trait-common-type.cpp | 126 ++++++++++++++
libcxx/include/__type_traits/common_type.h | 16 +-
libcxx/include/module.modulemap | 2 +
16 files changed, 404 insertions(+), 6 deletions(-)
create mode 100644 clang/test/SemaCXX/type-trait-common-type.cpp
diff --git a/clang/include/clang/AST/ASTContext.h
b/clang/include/clang/AST/ASTContext.h
index 608bd90fcc3ff..d02e742297898 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -399,6 +399,9 @@ class ASTContext : public RefCountedBase<ASTContext> {
/// The identifier '__type_pack_element'.
mutable IdentifierInfo *TypePackElementName = nullptr;
+ /// The identifier '__common_type'.
+ mutable IdentifierInfo *CommonTypeName = nullptr;
+
QualType ObjCConstantStringType;
mutable RecordDecl *CFConstantStringTagDecl = nullptr;
mutable TypedefDecl *CFConstantStringTypeDecl = nullptr;
@@ -606,6 +609,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
mutable ExternCContextDecl *ExternCContext = nullptr;
mutable BuiltinTemplateDecl *MakeIntegerSeqDecl = nullptr;
mutable BuiltinTemplateDecl *TypePackElementDecl = nullptr;
+ mutable BuiltinTemplateDecl *CommonTypeDecl = nullptr;
/// The associated SourceManager object.
SourceManager &SourceMgr;
@@ -1107,6 +1111,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
ExternCContextDecl *getExternCContextDecl() const;
BuiltinTemplateDecl *getMakeIntegerSeqDecl() const;
BuiltinTemplateDecl *getTypePackElementDecl() const;
+ BuiltinTemplateDecl *getCommonTypeDecl() const;
// Builtin Types.
CanQualType VoidTy;
@@ -1984,6 +1989,12 @@ class ASTContext : public RefCountedBase<ASTContext> {
return TypePackElementName;
}
+ IdentifierInfo *getCommonTypeName() const {
+ if (!CommonTypeName)
+ CommonTypeName = &Idents.get("__common_type");
+ return CommonTypeName;
+ }
+
/// Retrieve the Objective-C "instancetype" type, if already known;
/// otherwise, returns a NULL type;
QualType getObjCInstanceType() {
diff --git a/clang/include/clang/AST/DeclID.h b/clang/include/clang/AST/DeclID.h
index e5e27389fac60..875e9a72b3951 100644
--- a/clang/include/clang/AST/DeclID.h
+++ b/clang/include/clang/AST/DeclID.h
@@ -84,13 +84,16 @@ enum PredefinedDeclIDs {
/// The internal '__type_pack_element' template.
PREDEF_DECL_TYPE_PACK_ELEMENT_ID = 17,
+
+ /// The internal '__common_type' template.
+ PREDEF_DECL_COMMON_TYPE_ID = 18,
};
/// The number of declaration IDs that are predefined.
///
/// For more information about predefined declarations, see the
/// \c PredefinedDeclIDs type and the PREDEF_DECL_*_ID constants.
-const unsigned int NUM_PREDEF_DECL_IDS = 18;
+const unsigned int NUM_PREDEF_DECL_IDS = 19;
/// GlobalDeclID means DeclID in the current ASTContext and LocalDeclID means
/// DeclID specific to a certain ModuleFile. Specially, in ASTWriter, the
diff --git a/clang/include/clang/Basic/Builtins.h
b/clang/include/clang/Basic/Builtins.h
index e85ec5b2dca14..4353b72f71383 100644
--- a/clang/include/clang/Basic/Builtins.h
+++ b/clang/include/clang/Basic/Builtins.h
@@ -309,7 +309,10 @@ enum BuiltinTemplateKind : int {
BTK__make_integer_seq,
/// This names the __type_pack_element BuiltinTemplateDecl.
- BTK__type_pack_element
+ BTK__type_pack_element,
+
+ /// This names the __common_type BuiltinTemplateDecl.
+ BTK__common_type,
};
} // end namespace clang
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 3cb1aa935fe46..5c7945c4c5c58 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -2282,6 +2282,10 @@ class Sema final : public SemaBase {
/// Check to see if a given expression could have '.c_str()' called on it.
bool hasCStrMethod(const Expr *E);
+ // Check whether a type member 'Type::Name' exists, and if yes, return the
+ // type. If there is no type, the QualType is null
+ QualType getTypeMember(StringRef Name, QualType Type);
+
/// Diagnose pointers that are always non-null.
/// \param E the expression containing the pointer
/// \param NullKind NPCK_NotNull if E is a cast to bool, otherwise, E is
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index a8e599f7ebe04..b8b4f426ff96c 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -1170,6 +1170,13 @@ ASTContext::getTypePackElementDecl() const {
return TypePackElementDecl;
}
+BuiltinTemplateDecl *ASTContext::getCommonTypeDecl() const {
+ if (!CommonTypeDecl)
+ CommonTypeDecl =
+ buildBuiltinTemplateDecl(BTK__common_type, getCommonTypeName());
+ return CommonTypeDecl;
+}
+
RecordDecl *ASTContext::buildImplicitRecord(StringRef Name,
RecordDecl::TagKind TK) const {
SourceLocation Loc;
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 0c27f6f5df2da..e4515e19a49a3 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -5408,6 +5408,9 @@ ExpectedDecl
ASTNodeImporter::VisitBuiltinTemplateDecl(BuiltinTemplateDecl *D) {
case BuiltinTemplateKind::BTK__type_pack_element:
ToD = Importer.getToContext().getTypePackElementDecl();
break;
+ case BuiltinTemplateKind::BTK__common_type:
+ ToD = Importer.getToContext().getCommonTypeDecl();
+ break;
}
assert(ToD && "BuiltinTemplateDecl of unsupported kind!");
Importer.MapImported(D, ToD);
diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
index 722c7fcf0b0df..d290c91fb8290 100644
--- a/clang/lib/AST/DeclTemplate.cpp
+++ b/clang/lib/AST/DeclTemplate.cpp
@@ -1599,6 +1599,57 @@ createTypePackElementParameterList(const ASTContext &C,
DeclContext *DC) {
nullptr);
}
+static TemplateParameterList *createCommonTypeList(const ASTContext &C,
+ DeclContext *DC) {
+ // class... Args
+ auto *Args = TemplateTypeParmDecl::Create(
+ C, DC, {}, {}, /*Depth=*/1, /*Position=*/0, /*Id=*/nullptr,
+ /*Typename=*/false, /*ParameterPack=*/true);
+ Args->setImplicit();
+
+ // <class... Args>
+ auto *BaseTemplateList =
+ TemplateParameterList::Create(C, {}, {}, Args, {}, nullptr);
+
+ // template <class... Args> class BaseTemplate
+ auto *BaseTemplate = TemplateTemplateParmDecl::Create(
+ C, DC, {}, /*Depth=*/0, /*Position=*/0, /*ParameterPack=*/false, {},
+ /*Typename=*/false, BaseTemplateList);
+
+ // class TypeMember
+ auto *TypeMember = TemplateTypeParmDecl::Create(
+ C, DC, {}, {}, /*Depth=*/1, /*Position=*/0, /*Id=*/nullptr,
+ /*Typename=*/false, /*ParameterPack=*/false);
+
+ // <class TypeMember>
+ auto *HasTypeMemberList =
+ TemplateParameterList::Create(C, {}, {}, TypeMember, {}, nullptr);
+
+ // template <class TypeMember> class HasTypeMember
+ auto *HasTypeMember =
+ TemplateTemplateParmDecl::Create(C, DC, {}, /*Depth=*/0, /*Position=*/1,
+ /*ParameterPack=*/false, {},
+ /*Typename=*/false, HasTypeMemberList);
+
+ // class HasNoTypeMember
+ auto *HasNoTypeMember = TemplateTypeParmDecl::Create(
+ C, DC, {}, {}, /*Depth=*/0, /*Position=*/2, /*Id=*/nullptr,
+ /*Typename=*/false, /*ParameterPack=*/false);
+
+ // class... Ts
+ auto *Ts = TemplateTypeParmDecl::Create(
+ C, DC, {}, {}, /*Depth=*/0, /*Position=*/3,
+ /*Id=*/nullptr, /*Typename=*/false, /*ParameterPack=*/true);
+ Ts->setImplicit();
+
+ // template <template <class... Args> class BaseTemplate,
+ // template <class TypeMember> class HasTypeMember, class HasNoTypeMember,
+ // class... Ts>
+ return TemplateParameterList::Create(
+ C, {}, {}, {BaseTemplate, HasTypeMember, HasNoTypeMember, Ts}, {},
+ nullptr);
+}
+
static TemplateParameterList *createBuiltinTemplateParameterList(
const ASTContext &C, DeclContext *DC, BuiltinTemplateKind BTK) {
switch (BTK) {
@@ -1606,6 +1657,8 @@ static TemplateParameterList
*createBuiltinTemplateParameterList(
return createMakeIntegerSeqParameterList(C, DC);
case BTK__type_pack_element:
return createTypePackElementParameterList(C, DC);
+ case BTK__common_type:
+ return createCommonTypeList(C, DC);
}
llvm_unreachable("unhandled BuiltinTemplateKind!");
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp
b/clang/lib/Lex/PPMacroExpansion.cpp
index 3913ff08c2eb5..4a6dd13229fe0 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1822,6 +1822,7 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
// Report builtin templates as being builtins.
.Case("__make_integer_seq", getLangOpts().CPlusPlus)
.Case("__type_pack_element", getLangOpts().CPlusPlus)
+ .Case("__common_type", getLangOpts().CPlusPlus)
// Likewise for some builtin preprocessor macros.
// FIXME: This is inconsistent; we usually suggest detecting
// builtin macros via #ifdef. Don't add more cases here.
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 45b9bbb23dbf7..10c821fd367e7 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -6844,6 +6844,14 @@ CXXRecordMembersNamed(StringRef Name, Sema &S, QualType
Ty) {
return Results;
}
+QualType Sema::getTypeMember(StringRef Name, QualType Type) {
+ auto Results = CXXRecordMembersNamed<TypeDecl>(Name, *this, Type);
+ assert(Results.size() <= 1);
+ if (Results.empty())
+ return {};
+ return Context.getTypeDeclType(*Results.begin());
+}
+
/// Check if we could call '.c_str()' on an object.
///
/// FIXME: This returns the wrong results in some cases (if cv-qualifiers don't
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 7a6a64529f52e..96551c5106b1b 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -932,6 +932,10 @@ bool Sema::LookupBuiltin(LookupResult &R) {
R.addDecl(getASTContext().getTypePackElementDecl());
return true;
}
+ if (II == getASTContext().getCommonTypeName()) {
+ R.addDecl(getASTContext().getCommonTypeDecl());
+ return true;
+ }
}
// Check if this is an OpenCL Builtin, and if so, insert its overloads.
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 9d96201625389..bf3d35f0c1abb 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -3058,6 +3058,141 @@ void Sema::NoteAllFoundTemplates(TemplateName Name) {
}
}
+static std::optional<QualType> commonTypeImpl(Sema &S,
+ TemplateName BaseTemplate,
+ SourceLocation TemplateLoc,
+ ArrayRef<TemplateArgument> Ts) {
+ auto lookUpCommonType = [&](TemplateArgument T1,
+ TemplateArgument T2) -> std::optional<QualType> {
+ // Don't bother looking for other specializations if both types are
+ // builtins - users aren't allowed to specialize for them
+ if (T1.getAsType()->isBuiltinType() && T2.getAsType()->isBuiltinType())
+ return commonTypeImpl(S, BaseTemplate, TemplateLoc, {T1, T2});
+
+ TemplateArgumentListInfo Args;
+ Args.addArgument(TemplateArgumentLoc(
+ T1, S.Context.getTrivialTypeSourceInfo(T1.getAsType())));
+ Args.addArgument(TemplateArgumentLoc(
+ T2, S.Context.getTrivialTypeSourceInfo(T2.getAsType())));
+ QualType BaseTemplateInst =
+ S.CheckTemplateIdType(BaseTemplate, TemplateLoc, Args);
+ if (S.RequireCompleteType(TemplateLoc, BaseTemplateInst,
+ diag::err_incomplete_type))
+ return std::nullopt;
+ if (QualType Type = S.getTypeMember("type", BaseTemplateInst);
+ !Type.isNull()) {
+ return Type;
+ }
+ return std::nullopt;
+ };
+
+ // Note A: For the common_type trait applied to a template parameter pack T
of
+ // types, the member type shall be either defined or not present as follows:
+ switch (Ts.size()) {
+
+ // If sizeof...(T) is zero, there shall be no member type.
+ case 0:
+ return std::nullopt;
+
+ // If sizeof...(T) is one, let T0 denote the sole type constituting the
+ // pack T. The member typedef-name type shall denote the same type, if any,
as
+ // common_type_t<T0, T0>; otherwise there shall be no member type.
+ case 1:
+ return lookUpCommonType(Ts[0], Ts[0]);
+
+ // If sizeof...(T) is two, let the first and second types constituting T be
+ // denoted by T1 and T2, respectively, and let D1 and D2 denote the same
types
+ // as decay_t<T1> and decay_t<T2>, respectively.
+ case 2: {
+ QualType T1 = Ts[0].getAsType();
+ QualType T2 = Ts[1].getAsType();
+ QualType D1 = S.BuiltinDecay(T1, {});
+ QualType D2 = S.BuiltinDecay(T2, {});
+
+ // If is_same_v<T1, D1> is false or is_same_v<T2, D2> is false, let C
denote
+ // the same type, if any, as common_type_t<D1, D2>.
+ if (!S.Context.hasSameType(T1, D1) || !S.Context.hasSameType(T2, D2)) {
+ return lookUpCommonType(D1, D2);
+ }
+
+ // Otherwise, if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
+ // denotes a valid type, let C denote that type.
+ {
+ auto CheckConditionalOperands =
+ [&](bool ConstRefQual) -> std::optional<QualType> {
+ EnterExpressionEvaluationContext UnevaluatedContext(
+ S, Sema::ExpressionEvaluationContext::Unevaluated);
+ Sema::SFINAETrap SFINAE(S, /*AccessCheckingSFINAE=*/true);
+ Sema::ContextRAII TUContext(S, S.Context.getTranslationUnitDecl());
+
+ // false
+ OpaqueValueExpr CondExpr({}, S.Context.BoolTy,
+ ExprValueKind::VK_PRValue);
+ ExprResult Cond = &CondExpr;
+
+ auto EVK =
+ ConstRefQual ? ExprValueKind::VK_LValue :
ExprValueKind::VK_PRValue;
+ if (ConstRefQual) {
+ D1.addConst();
+ D2.addConst();
+ }
+
+ // declval<D1>()
+ OpaqueValueExpr LHSExpr(TemplateLoc, D1, EVK);
+ ExprResult LHS = &LHSExpr;
+
+ // declval<D2>()
+ OpaqueValueExpr RHSExpr(TemplateLoc, D2, EVK);
+ ExprResult RHS = &RHSExpr;
+
+ ExprValueKind VK = VK_PRValue;
+ ExprObjectKind OK = OK_Ordinary;
+
+ // decltype(false ? declval<D1>() : declval<D2>())
+ QualType Result =
+ S.CheckConditionalOperands(Cond, LHS, RHS, VK, OK, TemplateLoc);
+
+ if (Result.isNull() || SFINAE.hasErrorOccurred())
+ return std::nullopt;
+
+ // decay_t<decltype(false ? declval<D1>() : declval<D2>())>
+ return S.BuiltinDecay(Result, TemplateLoc);
+ };
+
+ if (auto Res = CheckConditionalOperands(false))
+ return Res;
+
+ // Let:
+ // CREF(A) be add_lvalue_reference_t<const remove_reference_t<A>>,
+ // COND-RES(X, Y) be
+ // decltype(false ? declval<X(&)()>()() : declval<Y(&)()>()()).
+
+ // C++20 only
+ // Otherwise, if COND-RES(CREF(D1), CREF(D2)) denotes a type, let C
denote
+ // the type decay_t<COND-RES(CREF(D1), CREF(D2))>.
+ if (!S.Context.getLangOpts().CPlusPlus20)
+ return std::nullopt;
+ return CheckConditionalOperands(true);
+ }
+ }
+
+ // If sizeof...(T) is greater than two, let T1, T2, and R, respectively,
+ // denote the first, second, and (pack of) remaining types constituting T.
Let
+ // C denote the same type, if any, as common_type_t<T1, T2>. If there is such
+ // a type C, the member typedef-name type shall denote the same type, if any,
+ // as common_type_t<C, R...>. Otherwise, there shall be no member type.
+ default: {
+ std::optional<QualType> Result = Ts[Ts.size() - 1].getAsType();
+ for (size_t i = Ts.size() - 1; i != 0; --i) {
+ Result = lookUpCommonType(Ts[i - 1].getAsType(), *Result);
+ if (!Result)
+ return std::nullopt;
+ }
+ return Result;
+ }
+ }
+}
+
static QualType
checkBuiltinTemplateIdType(Sema &SemaRef, BuiltinTemplateDecl *BTD,
ArrayRef<TemplateArgument> Converted,
@@ -3114,7 +3249,7 @@ checkBuiltinTemplateIdType(Sema &SemaRef,
BuiltinTemplateDecl *BTD,
TemplateLoc, SyntheticTemplateArgs);
}
- case BTK__type_pack_element:
+ case BTK__type_pack_element: {
// Specializations of
// __type_pack_element<Index, T_1, ..., T_N>
// are treated like T_Index.
@@ -3140,6 +3275,29 @@ checkBuiltinTemplateIdType(Sema &SemaRef,
BuiltinTemplateDecl *BTD,
int64_t N = Index.getExtValue();
return Ts.getPackAsArray()[N].getAsType();
}
+
+ case BTK__common_type: {
+ assert(Converted.size() == 4);
+ if (Converted[0].isDependent() || Converted[1].isDependent() ||
+ Converted[2].isDependent() || Converted[3].isDependent())
+ return Context.getCanonicalTemplateSpecializationType(TemplateName(BTD),
+ Converted);
+
+ TemplateName BaseTemplate = Converted[0].getAsTemplate();
+ TemplateName HasTypeMember = Converted[1].getAsTemplate();
+ QualType HasNoTypeMember = Converted[2].getAsType();
+ ArrayRef<TemplateArgument> Ts = Converted[3].getPackAsArray();
+ if (auto CT = commonTypeImpl(SemaRef, BaseTemplate, TemplateLoc, Ts)) {
+ TemplateArgumentListInfo TAs;
+ TAs.addArgument(TemplateArgumentLoc(
+ TemplateArgument(*CT), SemaRef.Context.getTrivialTypeSourceInfo(
+ *CT, TemplateArgs[1].getLocation())));
+
+ return SemaRef.CheckTemplateIdType(HasTypeMember, TemplateLoc, TAs);
+ }
+ return HasNoTypeMember;
+ }
+ }
llvm_unreachable("unexpected BuiltinTemplateDecl!");
}
diff --git a/clang/lib/Serialization/ASTReader.cpp
b/clang/lib/Serialization/ASTReader.cpp
index afdeccaf93a9d..40ebc2c5d020f 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -7789,6 +7789,9 @@ static Decl *getPredefinedDecl(ASTContext &Context,
PredefinedDeclIDs ID) {
case PREDEF_DECL_TYPE_PACK_ELEMENT_ID:
return Context.getTypePackElementDecl();
+
+ case PREDEF_DECL_COMMON_TYPE_ID:
+ return Context.getCommonTypeDecl();
}
llvm_unreachable("PredefinedDeclIDs unknown enum value");
}
diff --git a/clang/lib/Serialization/ASTWriter.cpp
b/clang/lib/Serialization/ASTWriter.cpp
index c78d8943d6d92..b17eeed357aac 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -5036,6 +5036,8 @@ void ASTWriter::PrepareWritingSpecialDecls(Sema &SemaRef)
{
PREDEF_DECL_CF_CONSTANT_STRING_TAG_ID);
RegisterPredefDecl(Context.TypePackElementDecl,
PREDEF_DECL_TYPE_PACK_ELEMENT_ID);
+ RegisterPredefDecl(Context.CommonTypeDecl,
+ PREDEF_DECL_COMMON_TYPE_ID);
const TranslationUnitDecl *TU = Context.getTranslationUnitDecl();
diff --git a/clang/test/SemaCXX/type-trait-common-type.cpp
b/clang/test/SemaCXX/type-trait-common-type.cpp
new file mode 100644
index 0000000000000..44207f066a333
--- /dev/null
+++ b/clang/test/SemaCXX/type-trait-common-type.cpp
@@ -0,0 +1,126 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fsyntax-only -verify
-std=c++17 %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fsyntax-only -verify
-std=c++20 %s
+
+#if !__has_builtin(__common_type)
+# error
+#endif
+
+// expected-note@*:* {{template declaration from hidden source: template
<class, template <class> class, class>}}
+
+void test() {
+ __common_type<> a; // expected-error {{too few template arguments for
template '__common_type'}}
+}
+
+struct empty_type {};
+
+template <class T>
+struct type_identity {
+ using type = T;
+};
+
+template <class...>
+struct common_type;
+
+template <class... Args>
+using common_type_base = __common_type<common_type, type_identity, empty_type,
Args...>; // expected-error {{incomplete type 'common_type<Incomplete,
Incomplete>' where a complete type is required}}
+
+template <class... Args>
+struct common_type : common_type_base<Args...> {};
+
+struct Incomplete;
+
+template<>
+struct common_type<Incomplete, Incomplete>; // expected-note {{forward
declaration}}
+
+static_assert(__is_same(common_type_base<>, empty_type));
+static_assert(__is_same(common_type_base<Incomplete>, empty_type)); //
expected-note {{requested here}}
+static_assert(__is_same(common_type_base<char>, type_identity<char>));
+static_assert(__is_same(common_type_base<int>, type_identity<int>));
+static_assert(__is_same(common_type_base<const int>, type_identity<int>));
+static_assert(__is_same(common_type_base<volatile int>, type_identity<int>));
+static_assert(__is_same(common_type_base<const volatile int>,
type_identity<int>));
+static_assert(__is_same(common_type_base<int[]>, type_identity<int*>));
+static_assert(__is_same(common_type_base<const int[]>, type_identity<const
int*>));
+static_assert(__is_same(common_type_base<void(&)()>,
type_identity<void(*)()>));
+static_assert(__is_same(common_type_base<int[], int[]>, type_identity<int*>));
+
+static_assert(__is_same(common_type_base<int, int>, type_identity<int>));
+static_assert(__is_same(common_type_base<int, long>, type_identity<long>));
+static_assert(__is_same(common_type_base<long, int>, type_identity<long>));
+static_assert(__is_same(common_type_base<long, long>, type_identity<long>));
+
+static_assert(__is_same(common_type_base<const int, long>,
type_identity<long>));
+static_assert(__is_same(common_type_base<const volatile int, long>,
type_identity<long>));
+static_assert(__is_same(common_type_base<int, const long>,
type_identity<long>));
+static_assert(__is_same(common_type_base<int, const volatile long>,
type_identity<long>));
+
+static_assert(__is_same(common_type_base<int*, long*>, empty_type));
+
+static_assert(__is_same(common_type_base<int, long, float>,
type_identity<float>));
+static_assert(__is_same(common_type_base<unsigned, char, long>,
type_identity<long>));
+static_assert(__is_same(common_type_base<long long, long long, long>,
type_identity<long long>));
+
+struct NoCommonType {};
+
+template <>
+struct common_type<NoCommonType, NoCommonType> {};
+
+struct CommonTypeInt {};
+
+template <>
+struct common_type<CommonTypeInt, CommonTypeInt> {
+ using type = int;
+};
+
+template <>
+struct common_type<CommonTypeInt, int> {
+ using type = int;
+};
+
+template <>
+struct common_type<int, CommonTypeInt> {
+ using type = int;
+};
+
+static_assert(__is_same(common_type_base<NoCommonType>, empty_type));
+static_assert(__is_same(common_type_base<CommonTypeInt>, type_identity<int>));
+static_assert(__is_same(common_type_base<NoCommonType, NoCommonType,
NoCommonType>, empty_type));
+static_assert(__is_same(common_type_base<CommonTypeInt, CommonTypeInt,
CommonTypeInt>, type_identity<int>));
+static_assert(__is_same(common_type_base<CommonTypeInt&, CommonTypeInt&&>,
type_identity<int>));
+
+static_assert(__is_same(common_type_base<void, int>, empty_type));
+static_assert(__is_same(common_type_base<void, void>, type_identity<void>));
+static_assert(__is_same(common_type_base<const void, void>,
type_identity<void>));
+static_assert(__is_same(common_type_base<void, const void>,
type_identity<void>));
+
+template <class T>
+struct ConvertibleTo {
+ operator T();
+};
+
+static_assert(__is_same(common_type_base<ConvertibleTo<int>>,
type_identity<ConvertibleTo<int>>));
+static_assert(__is_same(common_type_base<ConvertibleTo<int>, int>,
type_identity<int>));
+static_assert(__is_same(common_type_base<ConvertibleTo<int&>,
ConvertibleTo<long&>>, type_identity<long>));
+
+struct ConvertibleToB;
+
+struct ConvertibleToA {
+ operator ConvertibleToB();
+};
+
+struct ConvertibleToB {
+ operator ConvertibleToA();
+};
+
+static_assert(__is_same(common_type_base<ConvertibleToA, ConvertibleToB>,
empty_type));
+
+struct const_ref_convertible {
+ operator int&() const &;
+ operator int&() && = delete;
+};
+
+#if __cplusplus >= 202002L
+static_assert(__is_same(common_type_base<const_ref_convertible, int &>,
type_identity<int>));
+#else
+static_assert(__is_same(common_type_base<const_ref_convertible, int &>,
empty_type));
+#endif
diff --git a/libcxx/include/__type_traits/common_type.h
b/libcxx/include/__type_traits/common_type.h
index f6bd9ed71b7a4..103b58e42aa8a 100644
--- a/libcxx/include/__type_traits/common_type.h
+++ b/libcxx/include/__type_traits/common_type.h
@@ -14,8 +14,10 @@
#include <__type_traits/decay.h>
#include <__type_traits/is_same.h>
#include <__type_traits/remove_cvref.h>
+#include <__type_traits/type_identity.h>
#include <__type_traits/void_t.h>
#include <__utility/declval.h>
+#include <__utility/empty.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@@ -23,7 +25,13 @@
_LIBCPP_BEGIN_NAMESPACE_STD
-#if _LIBCPP_STD_VER >= 20
+#if __has_builtin(__common_type)
+
+template <class... _Args>
+struct common_type : __common_type<common_type, __type_identity, __empty,
_Args...> {};
+
+#else
+# if _LIBCPP_STD_VER >= 20
// Let COND_RES(X, Y) be:
template <class _Tp, class _Up>
using __cond_type = decltype(false ? std::declval<_Tp>() :
std::declval<_Up>());
@@ -39,10 +47,10 @@ struct __common_type3<_Tp, _Up, void_t<__cond_type<const
_Tp&, const _Up&>>> {
template <class _Tp, class _Up, class = void>
struct __common_type2_imp : __common_type3<_Tp, _Up> {};
-#else
+# else
template <class _Tp, class _Up, class = void>
struct __common_type2_imp {};
-#endif
+# endif
// sub-bullet 3 - "if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
..."
template <class _Tp, class _Up>
@@ -92,6 +100,8 @@ template <class _Tp, class _Up, class _Vp, class... _Rest>
struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up, _Vp, _Rest...>
: __common_type_impl<__common_types<_Tp, _Up, _Vp, _Rest...> > {};
+#endif
+
#if _LIBCPP_STD_VER >= 14
template <class... _Tp>
using common_type_t = typename common_type<_Tp...>::type;
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
index 7608aef3f3a43..4c15c514478f6 100644
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -1880,7 +1880,9 @@ module std_private_type_traits_common_reference
[system
}
module std_private_type_traits_common_type
[system] {
header "__type_traits/common_type.h"
+ export std_private_type_traits_type_identity
export std_private_utility_declval
+ export std_private_utility_empty
}
module std_private_type_traits_conditional
[system] { header "__type_traits/conditional.h" }
module std_private_type_traits_conjunction
[system] { header "__type_traits/conjunction.h" }
>From a912a763e1e4d8df4d472e64eff3ac800ab04068 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklau...@berlin.de>
Date: Thu, 25 Jul 2024 12:04:28 +0200
Subject: [PATCH 2/4] Address comment
---
clang/include/clang/Sema/Sema.h | 2 +-
clang/lib/AST/DeclTemplate.cpp | 39 +++++++-------
clang/lib/Sema/SemaChecking.cpp | 2 +-
clang/lib/Sema/SemaLookup.cpp | 3 +-
clang/lib/Sema/SemaTemplate.cpp | 54 +++++++++----------
clang/test/SemaCXX/type-trait-common-type.cpp | 46 +++++++++++++++-
libcxx/include/__type_traits/common_type.h | 9 +++-
7 files changed, 100 insertions(+), 55 deletions(-)
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 48c2fb86e7d9b..9ed20e71d61a6 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -2284,7 +2284,7 @@ class Sema final : public SemaBase {
// Check whether a type member 'Type::Name' exists, and if yes, return the
// type. If there is no type, the QualType is null
- QualType getTypeMember(StringRef Name, QualType Type);
+ QualType getTypeMember(QualType Type, StringRef Name);
/// Diagnose pointers that are always non-null.
/// \param E the expression containing the pointer
diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
index c40ff9b18ccff..c119d242bc292 100644
--- a/clang/lib/AST/DeclTemplate.cpp
+++ b/clang/lib/AST/DeclTemplate.cpp
@@ -1611,34 +1611,37 @@ createTypePackElementParameterList(const ASTContext &C,
DeclContext *DC) {
static TemplateParameterList *createCommonTypeList(const ASTContext &C,
DeclContext *DC) {
// class... Args
- auto *Args = TemplateTypeParmDecl::Create(
- C, DC, {}, {}, /*Depth=*/1, /*Position=*/0, /*Id=*/nullptr,
- /*Typename=*/false, /*ParameterPack=*/true);
- Args->setImplicit();
+ auto *Args =
+ TemplateTypeParmDecl::Create(C, DC, SourceLocation(), SourceLocation(),
+ /*Depth=*/1, /*Position=*/0, /*Id=*/nullptr,
+ /*Typename=*/false, /*ParameterPack=*/true);
// <class... Args>
- auto *BaseTemplateList =
- TemplateParameterList::Create(C, {}, {}, Args, {}, nullptr);
+ auto *BaseTemplateList = TemplateParameterList::Create(
+ C, SourceLocation(), SourceLocation(), Args, SourceLocation(), nullptr);
// template <class... Args> class BaseTemplate
auto *BaseTemplate = TemplateTemplateParmDecl::Create(
- C, DC, {}, /*Depth=*/0, /*Position=*/0, /*ParameterPack=*/false, {},
+ C, DC, SourceLocation(), /*Depth=*/0, /*Position=*/0,
+ /*ParameterPack=*/false, /*Id=*/nullptr,
/*Typename=*/false, BaseTemplateList);
// class TypeMember
- auto *TypeMember = TemplateTypeParmDecl::Create(
- C, DC, {}, {}, /*Depth=*/1, /*Position=*/0, /*Id=*/nullptr,
- /*Typename=*/false, /*ParameterPack=*/false);
+ auto *TypeMember =
+ TemplateTypeParmDecl::Create(C, DC, SourceLocation(), SourceLocation(),
+ /*Depth=*/1, /*Position=*/0, /*Id=*/nullptr,
+ /*Typename=*/false,
/*ParameterPack=*/false);
// <class TypeMember>
auto *HasTypeMemberList =
- TemplateParameterList::Create(C, {}, {}, TypeMember, {}, nullptr);
+ TemplateParameterList::Create(C, SourceLocation(), SourceLocation(),
+ TypeMember, SourceLocation(), nullptr);
// template <class TypeMember> class HasTypeMember
- auto *HasTypeMember =
- TemplateTemplateParmDecl::Create(C, DC, {}, /*Depth=*/0, /*Position=*/1,
- /*ParameterPack=*/false, {},
- /*Typename=*/false, HasTypeMemberList);
+ auto *HasTypeMember = TemplateTemplateParmDecl::Create(
+ C, DC, SourceLocation(), /*Depth=*/0, /*Position=*/1,
+ /*ParameterPack=*/false, /*Id=*/nullptr,
+ /*Typename=*/false, HasTypeMemberList);
// class HasNoTypeMember
auto *HasNoTypeMember = TemplateTypeParmDecl::Create(
@@ -1647,15 +1650,15 @@ static TemplateParameterList
*createCommonTypeList(const ASTContext &C,
// class... Ts
auto *Ts = TemplateTypeParmDecl::Create(
- C, DC, {}, {}, /*Depth=*/0, /*Position=*/3,
+ C, DC, SourceLocation(), SourceLocation(), /*Depth=*/0, /*Position=*/3,
/*Id=*/nullptr, /*Typename=*/false, /*ParameterPack=*/true);
- Ts->setImplicit();
// template <template <class... Args> class BaseTemplate,
// template <class TypeMember> class HasTypeMember, class HasNoTypeMember,
// class... Ts>
return TemplateParameterList::Create(
- C, {}, {}, {BaseTemplate, HasTypeMember, HasNoTypeMember, Ts}, {},
+ C, SourceLocation(), SourceLocation(),
+ {BaseTemplate, HasTypeMember, HasNoTypeMember, Ts}, SourceLocation(),
nullptr);
}
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 33e1442018f36..76135cfd5729f 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -6848,7 +6848,7 @@ CXXRecordMembersNamed(StringRef Name, Sema &S, QualType
Ty) {
return Results;
}
-QualType Sema::getTypeMember(StringRef Name, QualType Type) {
+QualType Sema::getTypeMember(QualType Type, StringRef Name) {
auto Results = CXXRecordMembersNamed<TypeDecl>(Name, *this, Type);
assert(Results.size() <= 1);
if (Results.empty())
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 96551c5106b1b..a9a80831e63b7 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -928,7 +928,8 @@ bool Sema::LookupBuiltin(LookupResult &R) {
if (II == getASTContext().getMakeIntegerSeqName()) {
R.addDecl(getASTContext().getMakeIntegerSeqDecl());
return true;
- } else if (II == getASTContext().getTypePackElementName()) {
+ }
+ if (II == getASTContext().getTypePackElementName()) {
R.addDecl(getASTContext().getTypePackElementDecl());
return true;
}
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index d73071c6bb95e..01bd2ec274699 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -3058,12 +3058,11 @@ void Sema::NoteAllFoundTemplates(TemplateName Name) {
}
}
-static std::optional<QualType> commonTypeImpl(Sema &S,
- TemplateName BaseTemplate,
- SourceLocation TemplateLoc,
- ArrayRef<TemplateArgument> Ts) {
+static QualType commonTypeImpl(Sema &S, TemplateName BaseTemplate,
+ SourceLocation TemplateLoc,
+ ArrayRef<TemplateArgument> Ts) {
auto lookUpCommonType = [&](TemplateArgument T1,
- TemplateArgument T2) -> std::optional<QualType> {
+ TemplateArgument T2) -> QualType {
// Don't bother looking for other specializations if both types are
// builtins - users aren't allowed to specialize for them
if (T1.getAsType()->isBuiltinType() && T2.getAsType()->isBuiltinType())
@@ -3078,12 +3077,8 @@ static std::optional<QualType> commonTypeImpl(Sema &S,
S.CheckTemplateIdType(BaseTemplate, TemplateLoc, Args);
if (S.RequireCompleteType(TemplateLoc, BaseTemplateInst,
diag::err_incomplete_type))
- return std::nullopt;
- if (QualType Type = S.getTypeMember("type", BaseTemplateInst);
- !Type.isNull()) {
- return Type;
- }
- return std::nullopt;
+ return QualType();
+ return S.getTypeMember(BaseTemplateInst, "type");
};
// Note A: For the common_type trait applied to a template parameter pack T
of
@@ -3092,7 +3087,7 @@ static std::optional<QualType> commonTypeImpl(Sema &S,
// If sizeof...(T) is zero, there shall be no member type.
case 0:
- return std::nullopt;
+ return QualType();
// If sizeof...(T) is one, let T0 denote the sole type constituting the
// pack T. The member typedef-name type shall denote the same type, if any,
as
@@ -3111,27 +3106,25 @@ static std::optional<QualType> commonTypeImpl(Sema &S,
// If is_same_v<T1, D1> is false or is_same_v<T2, D2> is false, let C
denote
// the same type, if any, as common_type_t<D1, D2>.
- if (!S.Context.hasSameType(T1, D1) || !S.Context.hasSameType(T2, D2)) {
+ if (!S.Context.hasSameType(T1, D1) || !S.Context.hasSameType(T2, D2))
return lookUpCommonType(D1, D2);
- }
// Otherwise, if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
// denotes a valid type, let C denote that type.
{
auto CheckConditionalOperands =
- [&](bool ConstRefQual) -> std::optional<QualType> {
+ [&](bool ConstRefQual) -> QualType {
EnterExpressionEvaluationContext UnevaluatedContext(
S, Sema::ExpressionEvaluationContext::Unevaluated);
Sema::SFINAETrap SFINAE(S, /*AccessCheckingSFINAE=*/true);
Sema::ContextRAII TUContext(S, S.Context.getTranslationUnitDecl());
// false
- OpaqueValueExpr CondExpr({}, S.Context.BoolTy,
- ExprValueKind::VK_PRValue);
+ OpaqueValueExpr CondExpr(SourceLocation(), S.Context.BoolTy,
+ VK_PRValue);
ExprResult Cond = &CondExpr;
- auto EVK =
- ConstRefQual ? ExprValueKind::VK_LValue :
ExprValueKind::VK_PRValue;
+ auto EVK = ConstRefQual ? VK_LValue : VK_PRValue;
if (ConstRefQual) {
D1.addConst();
D2.addConst();
@@ -3153,13 +3146,13 @@ static std::optional<QualType> commonTypeImpl(Sema &S,
S.CheckConditionalOperands(Cond, LHS, RHS, VK, OK, TemplateLoc);
if (Result.isNull() || SFINAE.hasErrorOccurred())
- return std::nullopt;
+ return QualType();
// decay_t<decltype(false ? declval<D1>() : declval<D2>())>
return S.BuiltinDecay(Result, TemplateLoc);
};
- if (auto Res = CheckConditionalOperands(false))
+ if (auto Res = CheckConditionalOperands(false); !Res.isNull())
return Res;
// Let:
@@ -3171,7 +3164,7 @@ static std::optional<QualType> commonTypeImpl(Sema &S,
// Otherwise, if COND-RES(CREF(D1), CREF(D2)) denotes a type, let C
denote
// the type decay_t<COND-RES(CREF(D1), CREF(D2))>.
if (!S.Context.getLangOpts().CPlusPlus20)
- return std::nullopt;
+ return QualType();
return CheckConditionalOperands(true);
}
}
@@ -3182,11 +3175,11 @@ static std::optional<QualType> commonTypeImpl(Sema &S,
// a type C, the member typedef-name type shall denote the same type, if any,
// as common_type_t<C, R...>. Otherwise, there shall be no member type.
default: {
- std::optional<QualType> Result = Ts[Ts.size() - 1].getAsType();
- for (size_t i = Ts.size() - 1; i != 0; --i) {
- Result = lookUpCommonType(Ts[i - 1].getAsType(), *Result);
- if (!Result)
- return std::nullopt;
+ QualType Result = Ts.front().getAsType();
+ for (auto T : llvm::drop_begin(Ts)) {
+ Result = lookUpCommonType(Result, T.getAsType());
+ if (Result.isNull())
+ return QualType();
}
return Result;
}
@@ -3287,11 +3280,12 @@ checkBuiltinTemplateIdType(Sema &SemaRef,
BuiltinTemplateDecl *BTD,
TemplateName HasTypeMember = Converted[1].getAsTemplate();
QualType HasNoTypeMember = Converted[2].getAsType();
ArrayRef<TemplateArgument> Ts = Converted[3].getPackAsArray();
- if (auto CT = commonTypeImpl(SemaRef, BaseTemplate, TemplateLoc, Ts)) {
+ if (auto CT = commonTypeImpl(SemaRef, BaseTemplate, TemplateLoc, Ts);
+ !CT.isNull()) {
TemplateArgumentListInfo TAs;
TAs.addArgument(TemplateArgumentLoc(
- TemplateArgument(*CT), SemaRef.Context.getTrivialTypeSourceInfo(
- *CT, TemplateArgs[1].getLocation())));
+ TemplateArgument(CT), SemaRef.Context.getTrivialTypeSourceInfo(
+ CT, TemplateArgs[1].getLocation())));
return SemaRef.CheckTemplateIdType(HasTypeMember, TemplateLoc, TAs);
}
diff --git a/clang/test/SemaCXX/type-trait-common-type.cpp
b/clang/test/SemaCXX/type-trait-common-type.cpp
index 44207f066a333..64d41d7db3e13 100644
--- a/clang/test/SemaCXX/type-trait-common-type.cpp
+++ b/clang/test/SemaCXX/type-trait-common-type.cpp
@@ -5,7 +5,7 @@
# error
#endif
-// expected-note@*:* {{template declaration from hidden source: template
<class, template <class> class, class>}}
+// expected-note@*:* {{template declaration from hidden source: template
<template <class ...> class, template <class> class, class, class ...>}}
void test() {
__common_type<> a; // expected-error {{too few template arguments for
template '__common_type'}}
@@ -22,7 +22,8 @@ template <class...>
struct common_type;
template <class... Args>
-using common_type_base = __common_type<common_type, type_identity, empty_type,
Args...>; // expected-error {{incomplete type 'common_type<Incomplete,
Incomplete>' where a complete type is required}}
+using common_type_base = __common_type<common_type, type_identity, empty_type,
Args...>;
+// expected-error@-1 {{incomplete type 'common_type<Incomplete, Incomplete>'
where a complete type is required}}
template <class... Args>
struct common_type : common_type_base<Args...> {};
@@ -124,3 +125,44 @@
static_assert(__is_same(common_type_base<const_ref_convertible, int &>, type_ide
#else
static_assert(__is_same(common_type_base<const_ref_convertible, int &>,
empty_type));
#endif
+
+struct WeirdConvertible_1p2_p3 {};
+
+struct WeirdConvertible3 {
+ operator WeirdConvertible_1p2_p3();
+};
+
+struct WeirdConvertible1p2 {
+ operator WeirdConvertible_1p2_p3();
+};
+
+template <>
+struct common_type<WeirdConvertible3, WeirdConvertible1p2> {
+ using type = WeirdConvertible_1p2_p3;
+};
+
+template <>
+struct common_type<WeirdConvertible1p2, WeirdConvertible3> {
+ using type = WeirdConvertible_1p2_p3;
+};
+
+struct WeirdConvertible1 {
+ operator WeirdConvertible1p2();
+};
+
+struct WeirdConvertible2 {
+ operator WeirdConvertible1p2();
+};
+
+template <>
+struct common_type<WeirdConvertible1, WeirdConvertible2> {
+ using type = WeirdConvertible1p2;
+};
+
+template <>
+struct common_type<WeirdConvertible2, WeirdConvertible1> {
+ using type = WeirdConvertible1p2;
+};
+
+static_assert(__is_same(common_type_base<WeirdConvertible1, WeirdConvertible2,
WeirdConvertible3>,
+ type_identity<WeirdConvertible_1p2_p3>));
diff --git a/libcxx/include/__type_traits/common_type.h
b/libcxx/include/__type_traits/common_type.h
index 103b58e42aa8a..c0cb1a5f80385 100644
--- a/libcxx/include/__type_traits/common_type.h
+++ b/libcxx/include/__type_traits/common_type.h
@@ -30,6 +30,11 @@ _LIBCPP_BEGIN_NAMESPACE_STD
template <class... _Args>
struct common_type : __common_type<common_type, __type_identity, __empty,
_Args...> {};
+#if _LIBCPP_STD_VER >= 14
+template <class... _Args>
+using common_type_t = typename __common_type<common_type, __type_identity,
__empty, _Args...>::type;
+#endif
+
#else
# if _LIBCPP_STD_VER >= 20
// Let COND_RES(X, Y) be:
@@ -100,13 +105,13 @@ template <class _Tp, class _Up, class _Vp, class... _Rest>
struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up, _Vp, _Rest...>
: __common_type_impl<__common_types<_Tp, _Up, _Vp, _Rest...> > {};
-#endif
-
#if _LIBCPP_STD_VER >= 14
template <class... _Tp>
using common_type_t = typename common_type<_Tp...>::type;
#endif
+#endif
+
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___TYPE_TRAITS_COMMON_TYPE_H
>From f418c260512dfd5c17918a5b6daddd76825c0433 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklau...@berlin.de>
Date: Thu, 25 Jul 2024 12:32:52 +0200
Subject: [PATCH 3/4] Add release note and documentation
---
clang/docs/LanguageExtensions.rst | 37 +++++++++++++++++++++++++++++++
clang/docs/ReleaseNotes.rst | 5 ++++-
2 files changed, 41 insertions(+), 1 deletion(-)
diff --git a/clang/docs/LanguageExtensions.rst
b/clang/docs/LanguageExtensions.rst
index 81784c75081ba..1c0f90f9cdfa4 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -1511,6 +1511,43 @@ Attributes (N2335)
C2
``#embed`` (N3017)
C23 C89, C++
============================================ ================================
============= =============
+Builtin type aliases
+====================
+
+Clang provides a few builtin aliases to improve the throughput of certain
metaprogramming facilities.
+
+__common_type
+-------------
+
+.. code-block:: c++
+ template <template <class... Args> class BaseTemplate,
+ template <class TypeMember> class HasTypeMember,
+ class HasNoTypeMember,
+ class... Ts>
+ using __common_type = ...;
+
+This alias is used for implementing ``std::common_type``. If
``std::common_type`` should contain a ``type`` member,
+it is an alias to ``HasTypeMember<TheCommonType>``. Otherwise it is an alias
to ``HasNoTypeMember``. The
+``BaseTemplate`` is usually ``std::common_type``. ``Ts`` are the arguments to
``std::common_type``.
+
+__type_pack_element
+-------------------
+
+.. code-block:: c++
+ template <std::size_t Index, class... Ts>
+ using __type_pack_element = ...;
+
+This alias returns the type at ``Index`` in the parameter pack ``Ts``.
+
+__make_integer_seq
+------------------
+
+.. code-block:: c++
+ template <template <class IntSeqT, IntSeqT... Ints> class IntSeq, class T,
class N>
+ using __make_integer_seq = ...;
+
+This alias returns ``IntSeq`` instantiated with ``IntSeqT = T``and ``Ints``
being the pack ``0, ..., N - 1``.
+
Type Trait Primitives
=====================
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 0b79e952b48af..734c571e85113 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -65,6 +65,9 @@ sections with improvements to Clang's support for those
languages.
C++ Language Changes
--------------------
+- The builtin type alias ``__common_type`` has been added to improve the
+ performance of ``std::common_type``.
+
C++17 Feature Support
^^^^^^^^^^^^^^^^^^^^^
@@ -117,7 +120,7 @@ Improvements to Clang's diagnostics
- Some template related diagnostics have been improved.
.. code-block:: c++
-
+
void foo() { template <typename> int i; } // error: templates can only be
declared in namespace or class scope
struct S {
>From eb8afc07f466bb9d13cfadad3d05fb01db9b17bf Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklau...@berlin.de>
Date: Thu, 25 Jul 2024 13:26:53 +0200
Subject: [PATCH 4/4] Try to fix CI; Address comment
---
clang/docs/LanguageExtensions.rst | 5 ++++-
clang/lib/Sema/SemaTemplate.cpp | 3 +--
clang/lib/Serialization/ASTWriter.cpp | 3 +--
libcxx/include/__type_traits/common_type.h | 9 ++-------
4 files changed, 8 insertions(+), 12 deletions(-)
diff --git a/clang/docs/LanguageExtensions.rst
b/clang/docs/LanguageExtensions.rst
index 1c0f90f9cdfa4..4aa5eadb48043 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -1520,6 +1520,7 @@ __common_type
-------------
.. code-block:: c++
+
template <template <class... Args> class BaseTemplate,
template <class TypeMember> class HasTypeMember,
class HasNoTypeMember,
@@ -1534,6 +1535,7 @@ __type_pack_element
-------------------
.. code-block:: c++
+
template <std::size_t Index, class... Ts>
using __type_pack_element = ...;
@@ -1543,7 +1545,8 @@ __make_integer_seq
------------------
.. code-block:: c++
- template <template <class IntSeqT, IntSeqT... Ints> class IntSeq, class T,
class N>
+
+ template <template <class IntSeqT, IntSeqT... Ints> class IntSeq, class T, T
N>
using __make_integer_seq = ...;
This alias returns ``IntSeq`` instantiated with ``IntSeqT = T``and ``Ints``
being the pack ``0, ..., N - 1``.
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 01bd2ec274699..0f7d47b8851d3 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -3112,8 +3112,7 @@ static QualType commonTypeImpl(Sema &S, TemplateName
BaseTemplate,
// Otherwise, if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
// denotes a valid type, let C denote that type.
{
- auto CheckConditionalOperands =
- [&](bool ConstRefQual) -> QualType {
+ auto CheckConditionalOperands = [&](bool ConstRefQual) -> QualType {
EnterExpressionEvaluationContext UnevaluatedContext(
S, Sema::ExpressionEvaluationContext::Unevaluated);
Sema::SFINAETrap SFINAE(S, /*AccessCheckingSFINAE=*/true);
diff --git a/clang/lib/Serialization/ASTWriter.cpp
b/clang/lib/Serialization/ASTWriter.cpp
index b17eeed357aac..7d8498edbce30 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -5036,8 +5036,7 @@ void ASTWriter::PrepareWritingSpecialDecls(Sema &SemaRef)
{
PREDEF_DECL_CF_CONSTANT_STRING_TAG_ID);
RegisterPredefDecl(Context.TypePackElementDecl,
PREDEF_DECL_TYPE_PACK_ELEMENT_ID);
- RegisterPredefDecl(Context.CommonTypeDecl,
- PREDEF_DECL_COMMON_TYPE_ID);
+ RegisterPredefDecl(Context.CommonTypeDecl, PREDEF_DECL_COMMON_TYPE_ID);
const TranslationUnitDecl *TU = Context.getTranslationUnitDecl();
diff --git a/libcxx/include/__type_traits/common_type.h
b/libcxx/include/__type_traits/common_type.h
index c0cb1a5f80385..103b58e42aa8a 100644
--- a/libcxx/include/__type_traits/common_type.h
+++ b/libcxx/include/__type_traits/common_type.h
@@ -30,11 +30,6 @@ _LIBCPP_BEGIN_NAMESPACE_STD
template <class... _Args>
struct common_type : __common_type<common_type, __type_identity, __empty,
_Args...> {};
-#if _LIBCPP_STD_VER >= 14
-template <class... _Args>
-using common_type_t = typename __common_type<common_type, __type_identity,
__empty, _Args...>::type;
-#endif
-
#else
# if _LIBCPP_STD_VER >= 20
// Let COND_RES(X, Y) be:
@@ -105,13 +100,13 @@ template <class _Tp, class _Up, class _Vp, class... _Rest>
struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up, _Vp, _Rest...>
: __common_type_impl<__common_types<_Tp, _Up, _Vp, _Rest...> > {};
+#endif
+
#if _LIBCPP_STD_VER >= 14
template <class... _Tp>
using common_type_t = typename common_type<_Tp...>::type;
#endif
-#endif
-
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___TYPE_TRAITS_COMMON_TYPE_H
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