ldionne updated this revision to Diff 48012.
ldionne added a comment.
Address some remaining issues:
- Rename __nth_element to __type_pack_element, as suggested by Richard Smith
- Fix template parameter position issue in createTypePackElementParameterList
AFAICT, the only remaining issue is whether we should produce a diagnostic when
the index is out of bounds, or whether this is reserved for standard
diagnostics and we should use another mean to report the error. This is a
trivial issue and I'll fix it or remove the TODO as soon as someone tells me
the right way to go.
I'm really hoping that we can move forward with this patch.
http://reviews.llvm.org/D15421
Files:
include/clang/AST/ASTContext.h
include/clang/AST/DeclTemplate.h
include/clang/Basic/Builtins.h
include/clang/Basic/DiagnosticSemaKinds.td
include/clang/Serialization/ASTBitCodes.h
lib/AST/ASTContext.cpp
lib/AST/DeclTemplate.cpp
lib/Lex/PPMacroExpansion.cpp
lib/Sema/SemaLookup.cpp
lib/Sema/SemaTemplate.cpp
lib/Serialization/ASTReader.cpp
lib/Serialization/ASTWriter.cpp
test/PCH/type_pack_element.cpp
test/SemaCXX/type_pack_element.cpp
Index: test/SemaCXX/type_pack_element.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/type_pack_element.cpp
@@ -0,0 +1,45 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
+
+static_assert(__has_builtin(__type_pack_element), "");
+
+using SizeT = decltype(sizeof(int));
+
+template <SizeT i, typename ...T>
+using TypePackElement = __type_pack_element<i, T...>;
+
+template <int i>
+struct X;
+
+static_assert(__is_same(TypePackElement<0, X<0>>, X<0>), "");
+
+static_assert(__is_same(TypePackElement<0, X<0>, X<1>>, X<0>), "");
+static_assert(__is_same(TypePackElement<1, X<0>, X<1>>, X<1>), "");
+
+static_assert(__is_same(TypePackElement<0, X<0>, X<1>, X<2>>, X<0>), "");
+static_assert(__is_same(TypePackElement<1, X<0>, X<1>, X<2>>, X<1>), "");
+static_assert(__is_same(TypePackElement<2, X<0>, X<1>, X<2>>, X<2>), "");
+
+static_assert(__is_same(TypePackElement<0, X<0>, X<1>, X<2>, X<3>>, X<0>), "");
+static_assert(__is_same(TypePackElement<1, X<0>, X<1>, X<2>, X<3>>, X<1>), "");
+static_assert(__is_same(TypePackElement<2, X<0>, X<1>, X<2>, X<3>>, X<2>), "");
+static_assert(__is_same(TypePackElement<3, X<0>, X<1>, X<2>, X<3>>, X<3>), "");
+
+static_assert(__is_same(TypePackElement<0, X<0>, X<1>, X<2>, X<3>, X<4>>, X<0>), "");
+static_assert(__is_same(TypePackElement<1, X<0>, X<1>, X<2>, X<3>, X<4>>, X<1>), "");
+static_assert(__is_same(TypePackElement<2, X<0>, X<1>, X<2>, X<3>, X<4>>, X<2>), "");
+static_assert(__is_same(TypePackElement<3, X<0>, X<1>, X<2>, X<3>, X<4>>, X<3>), "");
+static_assert(__is_same(TypePackElement<4, X<0>, X<1>, X<2>, X<3>, X<4>>, X<4>), "");
+
+static_assert(__is_same(TypePackElement<0, X<0>, X<1>, X<2>, X<3>, X<4>, X<5>>, X<0>), "");
+static_assert(__is_same(TypePackElement<1, X<0>, X<1>, X<2>, X<3>, X<4>, X<5>>, X<1>), "");
+static_assert(__is_same(TypePackElement<2, X<0>, X<1>, X<2>, X<3>, X<4>, X<5>>, X<2>), "");
+static_assert(__is_same(TypePackElement<3, X<0>, X<1>, X<2>, X<3>, X<4>, X<5>>, X<3>), "");
+static_assert(__is_same(TypePackElement<4, X<0>, X<1>, X<2>, X<3>, X<4>, X<5>>, X<4>), "");
+static_assert(__is_same(TypePackElement<5, X<0>, X<1>, X<2>, X<3>, X<4>, X<5>>, X<5>), "");
+
+// Test __type_pack_element with more than 2 top-level template arguments.
+static_assert(__is_same(__type_pack_element<5, X<0>, X<1>, X<2>, X<3>, X<4>, X<5>>, X<5>), "");
+
+template <SizeT Index, typename ...T>
+using ErrorTypePackElement1 = __type_pack_element<Index, T...>; // expected-error{{may not be accessed at an out of bounds index}}
+using illformed1 = ErrorTypePackElement1<3, X<0>, X<1>>; // expected-note{{in instantiation}}
Index: test/PCH/type_pack_element.cpp
===================================================================
--- /dev/null
+++ test/PCH/type_pack_element.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -std=c++14 -x c++-header %s -emit-pch -o %t.pch
+// RUN: %clang_cc1 -std=c++14 -x c++ /dev/null -include-pch %t.pch
+
+template <int i>
+struct X { };
+
+using SizeT = decltype(sizeof(int));
+
+template <SizeT i, typename ...T>
+using TypePackElement = __type_pack_element<i, T...>;
+
+void fn1() {
+ X<0> x0 = TypePackElement<0, X<0>, X<1>, X<2>>{};
+ X<1> x1 = TypePackElement<1, X<0>, X<1>, X<2>>{};
+ X<2> x2 = TypePackElement<2, X<0>, X<1>, X<2>>{};
+}
Index: lib/Serialization/ASTWriter.cpp
===================================================================
--- lib/Serialization/ASTWriter.cpp
+++ lib/Serialization/ASTWriter.cpp
@@ -4182,6 +4182,8 @@
PREDEF_DECL_CF_CONSTANT_STRING_ID);
RegisterPredefDecl(Context.CFConstantStringTagDecl,
PREDEF_DECL_CF_CONSTANT_STRING_TAG_ID);
+ RegisterPredefDecl(Context.TypePackElementDecl,
+ PREDEF_DECL_TYPE_PACK_ELEMENT_ID);
// Build a record containing all of the tentative definitions in this file, in
// TentativeDefinitions order. Generally, this record will be empty for
Index: lib/Serialization/ASTReader.cpp
===================================================================
--- lib/Serialization/ASTReader.cpp
+++ lib/Serialization/ASTReader.cpp
@@ -6463,6 +6463,9 @@
case PREDEF_DECL_CF_CONSTANT_STRING_TAG_ID:
return Context.getCFConstantStringTagDecl();
+
+ case PREDEF_DECL_TYPE_PACK_ELEMENT_ID:
+ return Context.getTypePackElementDecl();
}
llvm_unreachable("PredefinedDeclIDs unknown enum value");
}
Index: lib/Sema/SemaTemplate.cpp
===================================================================
--- lib/Sema/SemaTemplate.cpp
+++ lib/Sema/SemaTemplate.cpp
@@ -33,6 +33,7 @@
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
+#include <iterator>
using namespace clang;
using namespace sema;
@@ -2027,7 +2028,7 @@
TemplateArgumentListInfo &TemplateArgs) {
ASTContext &Context = SemaRef.getASTContext();
switch (BTD->getBuiltinTemplateKind()) {
- case BTK__make_integer_seq:
+ case BTK__make_integer_seq: {
// Specializations of __make_integer_seq<S, T, N> are treated like
// S<T, 0, ..., N-1>.
@@ -2069,6 +2070,33 @@
return SemaRef.CheckTemplateIdType(Converted[0].getAsTemplate(),
TemplateLoc, SyntheticTemplateArgs);
}
+
+ case BTK__type_pack_element:
+ // Specializations of
+ // __type_pack_element<Index, T_1, ..., T_N>
+ // are treated like T_Index.
+ assert(Converted.size() == 2 &&
+ "__type_pack_element should be given an index and a parameter pack");
+
+ // If the Index is out of bounds, the program is ill-formed.
+ //
+ // TODO:
+ // This is not actually mandated by the standard, of course, so does it
+ // have its place here?
+ TemplateArgument IndexArg = Converted[0], Ts = Converted[1];
+ llvm::APSInt Index = IndexArg.getAsIntegral();
+ assert(Index >= 0 && "the index used with __type_pack_element should be of "
+ "type std::size_t, and hence be non-negative");
+ if (Index >= Ts.pack_size()) {
+ SemaRef.Diag(TemplateArgs[0].getLocation(),
+ diag::err_type_pack_element_out_of_bounds);
+ return QualType();
+ }
+
+ // We simply return the type at index `Index`.
+ auto Nth = std::next(Ts.pack_begin(), Index.getExtValue());
+ return Nth->getAsType();
+ }
llvm_unreachable("unexpected BuiltinTemplateDecl!");
}
Index: lib/Sema/SemaLookup.cpp
===================================================================
--- lib/Sema/SemaLookup.cpp
+++ lib/Sema/SemaLookup.cpp
@@ -672,10 +672,14 @@
R.addDecl(S.getASTContext().getFloat128StubType());
return true;
}
- if (S.getLangOpts().CPlusPlus && NameKind == Sema::LookupOrdinaryName &&
- II == S.getASTContext().getMakeIntegerSeqName()) {
- R.addDecl(S.getASTContext().getMakeIntegerSeqDecl());
- return true;
+ if (S.getLangOpts().CPlusPlus && NameKind == Sema::LookupOrdinaryName) {
+ if (II == S.getASTContext().getMakeIntegerSeqName()) {
+ R.addDecl(S.getASTContext().getMakeIntegerSeqDecl());
+ return true;
+ } else if (II == S.getASTContext().getTypePackElementName()) {
+ R.addDecl(S.getASTContext().getTypePackElementDecl());
+ return true;
+ }
}
// If this is a builtin on this (or all) targets, create the decl.
Index: lib/Lex/PPMacroExpansion.cpp
===================================================================
--- lib/Lex/PPMacroExpansion.cpp
+++ lib/Lex/PPMacroExpansion.cpp
@@ -1644,6 +1644,7 @@
StringRef Feature = FeatureII->getName();
Value = llvm::StringSwitch<bool>(Feature)
.Case("__make_integer_seq", getLangOpts().CPlusPlus)
+ .Case("__type_pack_element", getLangOpts().CPlusPlus)
.Default(false);
}
} else if (II == Ident__has_attribute)
Index: lib/AST/DeclTemplate.cpp
===================================================================
--- lib/AST/DeclTemplate.cpp
+++ lib/AST/DeclTemplate.cpp
@@ -1239,11 +1239,34 @@
Params, SourceLocation());
}
+static TemplateParameterList *
+createTypePackElementParameterList(const ASTContext &C, DeclContext *DC) {
+ // std::size_t Index
+ TypeSourceInfo *TInfo = C.getTrivialTypeSourceInfo(C.getSizeType());
+ auto *Index = NonTypeTemplateParmDecl::Create(
+ C, DC, SourceLocation(), SourceLocation(), /*Depth=*/0, /*Position=*/0,
+ /*Id=*/nullptr, TInfo->getType(), /*ParameterPack=*/false, TInfo);
+
+ // typename ...T
+ auto *Ts = TemplateTypeParmDecl::Create(
+ C, DC, SourceLocation(), SourceLocation(), /*Depth=*/0, /*Position=*/1,
+ /*Id=*/nullptr, /*Typename=*/true, /*ParameterPack=*/true);
+ Ts->setImplicit(true);
+
+ // template <std::size_t Index, typename ...T>
+ NamedDecl *Params[] = {Index, Ts};
+ return TemplateParameterList::Create(C, SourceLocation(), SourceLocation(),
+ llvm::makeArrayRef(Params),
+ SourceLocation());
+}
+
static TemplateParameterList *createBuiltinTemplateParameterList(
const ASTContext &C, DeclContext *DC, BuiltinTemplateKind BTK) {
switch (BTK) {
case BTK__make_integer_seq:
return createMakeIntegerSeqParameterList(C, DC);
+ case BTK__type_pack_element:
+ return createTypePackElementParameterList(C, DC);
}
llvm_unreachable("unhandled BuiltinTemplateKind!");
Index: lib/AST/ASTContext.cpp
===================================================================
--- lib/AST/ASTContext.cpp
+++ lib/AST/ASTContext.cpp
@@ -743,8 +743,8 @@
sigjmp_bufDecl(nullptr), ucontext_tDecl(nullptr),
BlockDescriptorType(nullptr), BlockDescriptorExtendedType(nullptr),
cudaConfigureCallDecl(nullptr), FirstLocalImport(), LastLocalImport(),
- ExternCContext(nullptr), MakeIntegerSeqDecl(nullptr), SourceMgr(SM),
- LangOpts(LOpts),
+ ExternCContext(nullptr), MakeIntegerSeqDecl(nullptr),
+ TypePackElementDecl(nullptr), SourceMgr(SM), LangOpts(LOpts),
SanitizerBL(new SanitizerBlacklist(LangOpts.SanitizerBlacklistFiles, SM)),
AddrSpaceMap(nullptr), Target(nullptr), AuxTarget(nullptr),
PrintingPolicy(LOpts), Idents(idents), Selectors(sels),
@@ -929,6 +929,14 @@
return MakeIntegerSeqDecl;
}
+BuiltinTemplateDecl *
+ASTContext::getTypePackElementDecl() const {
+ if (!TypePackElementDecl)
+ TypePackElementDecl = buildBuiltinTemplateDecl(BTK__type_pack_element,
+ getTypePackElementName());
+ return TypePackElementDecl;
+}
+
RecordDecl *ASTContext::buildImplicitRecord(StringRef Name,
RecordDecl::TagKind TK) const {
SourceLocation Loc;
Index: include/clang/Serialization/ASTBitCodes.h
===================================================================
--- include/clang/Serialization/ASTBitCodes.h
+++ include/clang/Serialization/ASTBitCodes.h
@@ -996,13 +996,16 @@
/// \brief The internal '__NSConstantString' tag type.
PREDEF_DECL_CF_CONSTANT_STRING_TAG_ID = 15,
+
+ /// \brief The internal '__type_pack_element' template.
+ PREDEF_DECL_TYPE_PACK_ELEMENT_ID = 16,
};
/// \brief 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 = 16;
+ const unsigned int NUM_PREDEF_DECL_IDS = 17;
/// \brief Record code for a list of local redeclarations of a declaration.
const unsigned int LOCAL_REDECLARATIONS = 50;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -2095,6 +2095,10 @@
def err_integer_sequence_integral_element_type : Error<
"integer sequences must have integral element type">;
+// __type_pack_element
+def err_type_pack_element_out_of_bounds : Error<
+ "a parameter pack may not be accessed at an out of bounds index">;
+
// Objective-C++
def err_objc_decls_may_only_appear_in_global_scope : Error<
"Objective-C declarations may only appear in global scope">;
Index: include/clang/Basic/Builtins.h
===================================================================
--- include/clang/Basic/Builtins.h
+++ include/clang/Basic/Builtins.h
@@ -214,7 +214,10 @@
/// \brief Kinds of BuiltinTemplateDecl.
enum BuiltinTemplateKind : int {
/// \brief This names the __make_integer_seq BuiltinTemplateDecl.
- BTK__make_integer_seq
+ BTK__make_integer_seq,
+
+ /// \brief This names the __type_pack_element BuiltinTemplateDecl.
+ BTK__type_pack_element
};
} // end namespace clang
Index: include/clang/AST/DeclTemplate.h
===================================================================
--- include/clang/AST/DeclTemplate.h
+++ include/clang/AST/DeclTemplate.h
@@ -1489,8 +1489,8 @@
};
/// \brief Represents the builtin template declaration which is used to
-/// implement __make_integer_seq. It serves no real purpose beyond existing as
-/// a place to hold template parameters.
+/// implement __make_integer_seq and other builtin templates. It serves
+/// no real purpose beyond existing as a place to hold template parameters.
class BuiltinTemplateDecl : public TemplateDecl {
void anchor() override;
Index: include/clang/AST/ASTContext.h
===================================================================
--- include/clang/AST/ASTContext.h
+++ include/clang/AST/ASTContext.h
@@ -252,6 +252,9 @@
/// The identifier '__make_integer_seq'.
mutable IdentifierInfo *MakeIntegerSeqName = nullptr;
+ /// The identifier '__type_pack_element'.
+ mutable IdentifierInfo *TypePackElementName = nullptr;
+
QualType ObjCConstantStringType;
mutable RecordDecl *CFConstantStringTagDecl;
mutable TypedefDecl *CFConstantStringTypeDecl;
@@ -407,6 +410,7 @@
TranslationUnitDecl *TUDecl;
mutable ExternCContextDecl *ExternCContext;
mutable BuiltinTemplateDecl *MakeIntegerSeqDecl;
+ mutable BuiltinTemplateDecl *TypePackElementDecl;
/// \brief The associated SourceManager object.a
SourceManager &SourceMgr;
@@ -877,6 +881,7 @@
ExternCContextDecl *getExternCContextDecl() const;
BuiltinTemplateDecl *getMakeIntegerSeqDecl() const;
+ BuiltinTemplateDecl *getTypePackElementDecl() const;
// Builtin Types.
CanQualType VoidTy;
@@ -1467,6 +1472,12 @@
return MakeIntegerSeqName;
}
+ IdentifierInfo *getTypePackElementName() const {
+ if (!TypePackElementName)
+ TypePackElementName = &Idents.get("__type_pack_element");
+ return TypePackElementName;
+ }
+
/// \brief Retrieve the Objective-C "instancetype" type, if already known;
/// otherwise, returns a NULL type;
QualType getObjCInstanceType() {
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