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Sirraide d09048a464 [Clang] [C++26] Expansion Statements (P1306R5) (#169680)
This implements C++26's expansion statements, i.e.
[P1306R5](https://wg21.link/P1306R5).

An expansion statement is implemented using a number of new AST
nodes. Since an expansion statement is a template, we need it to be
a dependent DeclContext, but only nodes that inherit from Decl can
be DeclContexts, for which reason this introduces a CXXExpansionStmtDecl.
This holds a synthesised constant template parameter used as the
expansion index as well as a 'CXXExpansionStmtPattern' and a
'CXXExpansionStmtInstantiation.

These two AST nodes are similar to the semantic vs syntactic form
of an InitListExpr: the 'Pattern' represents an unexpanded expansion
statement, and the resulting AST after expansion is stored in an
'Instantiation'.

Since expansion statements require us to perform template instantiation
*inside* a function without instantiating the rest of a function, I had to
remove a number of assertions in the template instantiation engine (e.g.
the assertion that a function parameter must always have an instantiation 
by the time we encounter a DeclRefExpr to it no longer holds).

For more implementation details, see the corresponding doc comments
in DeclTemplate.h and StmtCXX.h.

There is some follow up work to be done after this lands, which is
tracked in #207776.
2026-07-11 00:01:08 +02:00

518 lines
15 KiB
C++

//===--- ASTCommon.cpp - Common stuff for ASTReader/ASTWriter----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines common functions that both ASTReader and ASTWriter use.
//
//===----------------------------------------------------------------------===//
#include "ASTCommon.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/Basic/IdentifierTable.h"
#include "clang/Serialization/ASTDeserializationListener.h"
#include "llvm/Support/DJB.h"
using namespace clang;
// Give ASTDeserializationListener's VTable a home.
ASTDeserializationListener::~ASTDeserializationListener() { }
serialization::TypeIdx
serialization::TypeIdxFromBuiltin(const BuiltinType *BT) {
unsigned ID = 0;
switch (BT->getKind()) {
case BuiltinType::Void:
ID = PREDEF_TYPE_VOID_ID;
break;
case BuiltinType::Bool:
ID = PREDEF_TYPE_BOOL_ID;
break;
case BuiltinType::Char_U:
ID = PREDEF_TYPE_CHAR_U_ID;
break;
case BuiltinType::UChar:
ID = PREDEF_TYPE_UCHAR_ID;
break;
case BuiltinType::UShort:
ID = PREDEF_TYPE_USHORT_ID;
break;
case BuiltinType::UInt:
ID = PREDEF_TYPE_UINT_ID;
break;
case BuiltinType::ULong:
ID = PREDEF_TYPE_ULONG_ID;
break;
case BuiltinType::ULongLong:
ID = PREDEF_TYPE_ULONGLONG_ID;
break;
case BuiltinType::UInt128:
ID = PREDEF_TYPE_UINT128_ID;
break;
case BuiltinType::Char_S:
ID = PREDEF_TYPE_CHAR_S_ID;
break;
case BuiltinType::SChar:
ID = PREDEF_TYPE_SCHAR_ID;
break;
case BuiltinType::WChar_S:
case BuiltinType::WChar_U:
ID = PREDEF_TYPE_WCHAR_ID;
break;
case BuiltinType::Short:
ID = PREDEF_TYPE_SHORT_ID;
break;
case BuiltinType::Int:
ID = PREDEF_TYPE_INT_ID;
break;
case BuiltinType::Long:
ID = PREDEF_TYPE_LONG_ID;
break;
case BuiltinType::LongLong:
ID = PREDEF_TYPE_LONGLONG_ID;
break;
case BuiltinType::Int128:
ID = PREDEF_TYPE_INT128_ID;
break;
case BuiltinType::Half:
ID = PREDEF_TYPE_HALF_ID;
break;
case BuiltinType::Float:
ID = PREDEF_TYPE_FLOAT_ID;
break;
case BuiltinType::Double:
ID = PREDEF_TYPE_DOUBLE_ID;
break;
case BuiltinType::LongDouble:
ID = PREDEF_TYPE_LONGDOUBLE_ID;
break;
case BuiltinType::ShortAccum:
ID = PREDEF_TYPE_SHORT_ACCUM_ID;
break;
case BuiltinType::Accum:
ID = PREDEF_TYPE_ACCUM_ID;
break;
case BuiltinType::LongAccum:
ID = PREDEF_TYPE_LONG_ACCUM_ID;
break;
case BuiltinType::UShortAccum:
ID = PREDEF_TYPE_USHORT_ACCUM_ID;
break;
case BuiltinType::UAccum:
ID = PREDEF_TYPE_UACCUM_ID;
break;
case BuiltinType::ULongAccum:
ID = PREDEF_TYPE_ULONG_ACCUM_ID;
break;
case BuiltinType::ShortFract:
ID = PREDEF_TYPE_SHORT_FRACT_ID;
break;
case BuiltinType::Fract:
ID = PREDEF_TYPE_FRACT_ID;
break;
case BuiltinType::LongFract:
ID = PREDEF_TYPE_LONG_FRACT_ID;
break;
case BuiltinType::UShortFract:
ID = PREDEF_TYPE_USHORT_FRACT_ID;
break;
case BuiltinType::UFract:
ID = PREDEF_TYPE_UFRACT_ID;
break;
case BuiltinType::ULongFract:
ID = PREDEF_TYPE_ULONG_FRACT_ID;
break;
case BuiltinType::SatShortAccum:
ID = PREDEF_TYPE_SAT_SHORT_ACCUM_ID;
break;
case BuiltinType::SatAccum:
ID = PREDEF_TYPE_SAT_ACCUM_ID;
break;
case BuiltinType::SatLongAccum:
ID = PREDEF_TYPE_SAT_LONG_ACCUM_ID;
break;
case BuiltinType::SatUShortAccum:
ID = PREDEF_TYPE_SAT_USHORT_ACCUM_ID;
break;
case BuiltinType::SatUAccum:
ID = PREDEF_TYPE_SAT_UACCUM_ID;
break;
case BuiltinType::SatULongAccum:
ID = PREDEF_TYPE_SAT_ULONG_ACCUM_ID;
break;
case BuiltinType::SatShortFract:
ID = PREDEF_TYPE_SAT_SHORT_FRACT_ID;
break;
case BuiltinType::SatFract:
ID = PREDEF_TYPE_SAT_FRACT_ID;
break;
case BuiltinType::SatLongFract:
ID = PREDEF_TYPE_SAT_LONG_FRACT_ID;
break;
case BuiltinType::SatUShortFract:
ID = PREDEF_TYPE_SAT_USHORT_FRACT_ID;
break;
case BuiltinType::SatUFract:
ID = PREDEF_TYPE_SAT_UFRACT_ID;
break;
case BuiltinType::SatULongFract:
ID = PREDEF_TYPE_SAT_ULONG_FRACT_ID;
break;
case BuiltinType::Float16:
ID = PREDEF_TYPE_FLOAT16_ID;
break;
case BuiltinType::Float128:
ID = PREDEF_TYPE_FLOAT128_ID;
break;
case BuiltinType::Ibm128:
ID = PREDEF_TYPE_IBM128_ID;
break;
case BuiltinType::NullPtr:
ID = PREDEF_TYPE_NULLPTR_ID;
break;
case BuiltinType::Char8:
ID = PREDEF_TYPE_CHAR8_ID;
break;
case BuiltinType::Char16:
ID = PREDEF_TYPE_CHAR16_ID;
break;
case BuiltinType::Char32:
ID = PREDEF_TYPE_CHAR32_ID;
break;
case BuiltinType::Overload:
ID = PREDEF_TYPE_OVERLOAD_ID;
break;
case BuiltinType::UnresolvedTemplate:
ID = PREDEF_TYPE_UNRESOLVED_TEMPLATE;
break;
case BuiltinType::BoundMember:
ID = PREDEF_TYPE_BOUND_MEMBER;
break;
case BuiltinType::PseudoObject:
ID = PREDEF_TYPE_PSEUDO_OBJECT;
break;
case BuiltinType::Dependent:
ID = PREDEF_TYPE_DEPENDENT_ID;
break;
case BuiltinType::UnknownAny:
ID = PREDEF_TYPE_UNKNOWN_ANY;
break;
case BuiltinType::ARCUnbridgedCast:
ID = PREDEF_TYPE_ARC_UNBRIDGED_CAST;
break;
case BuiltinType::ObjCId:
ID = PREDEF_TYPE_OBJC_ID;
break;
case BuiltinType::ObjCClass:
ID = PREDEF_TYPE_OBJC_CLASS;
break;
case BuiltinType::ObjCSel:
ID = PREDEF_TYPE_OBJC_SEL;
break;
#define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
case BuiltinType::Id: \
ID = PREDEF_TYPE_##Id##_ID; \
break;
#include "clang/Basic/OpenCLImageTypes.def"
#define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
case BuiltinType::Id: \
ID = PREDEF_TYPE_##Id##_ID; \
break;
#include "clang/Basic/OpenCLExtensionTypes.def"
case BuiltinType::OCLSampler:
ID = PREDEF_TYPE_SAMPLER_ID;
break;
case BuiltinType::OCLEvent:
ID = PREDEF_TYPE_EVENT_ID;
break;
case BuiltinType::OCLClkEvent:
ID = PREDEF_TYPE_CLK_EVENT_ID;
break;
case BuiltinType::OCLQueue:
ID = PREDEF_TYPE_QUEUE_ID;
break;
case BuiltinType::OCLReserveID:
ID = PREDEF_TYPE_RESERVE_ID_ID;
break;
#define SVE_TYPE(Name, Id, SingletonId) \
case BuiltinType::Id: \
ID = PREDEF_TYPE_##Id##_ID; \
break;
#include "clang/Basic/AArch64ACLETypes.def"
#define PPC_VECTOR_TYPE(Name, Id, Size) \
case BuiltinType::Id: \
ID = PREDEF_TYPE_##Id##_ID; \
break;
#include "clang/Basic/PPCTypes.def"
#define RVV_TYPE(Name, Id, SingletonId) \
case BuiltinType::Id: \
ID = PREDEF_TYPE_##Id##_ID; \
break;
#include "clang/Basic/RISCVVTypes.def"
#define WASM_TYPE(Name, Id, SingletonId) \
case BuiltinType::Id: \
ID = PREDEF_TYPE_##Id##_ID; \
break;
#include "clang/Basic/WebAssemblyReferenceTypes.def"
#define AMDGPU_TYPE(Name, Id, SingletonId, Width, Align) \
case BuiltinType::Id: \
ID = PREDEF_TYPE_##Id##_ID; \
break;
#include "clang/Basic/AMDGPUTypes.def"
#define HLSL_INTANGIBLE_TYPE(Name, Id, SingletonId) \
case BuiltinType::Id: \
ID = PREDEF_TYPE_##Id##_ID; \
break;
#include "clang/Basic/HLSLIntangibleTypes.def"
case BuiltinType::BuiltinFn:
ID = PREDEF_TYPE_BUILTIN_FN;
break;
case BuiltinType::IncompleteMatrixIdx:
ID = PREDEF_TYPE_INCOMPLETE_MATRIX_IDX;
break;
case BuiltinType::ArraySection:
ID = PREDEF_TYPE_ARRAY_SECTION;
break;
case BuiltinType::OMPArrayShaping:
ID = PREDEF_TYPE_OMP_ARRAY_SHAPING;
break;
case BuiltinType::OMPIterator:
ID = PREDEF_TYPE_OMP_ITERATOR;
break;
case BuiltinType::BFloat16:
ID = PREDEF_TYPE_BFLOAT16_ID;
break;
}
return TypeIdx(0, ID);
}
unsigned serialization::ComputeHash(Selector Sel) {
unsigned N = Sel.getNumArgs();
if (N == 0)
++N;
unsigned R = 5381;
for (unsigned I = 0; I != N; ++I)
if (const IdentifierInfo *II = Sel.getIdentifierInfoForSlot(I))
R = llvm::djbHash(II->getName(), R);
return R;
}
const DeclContext *
serialization::getDefinitiveDeclContext(const DeclContext *DC) {
switch (DC->getDeclKind()) {
// These entities may have multiple definitions.
case Decl::TranslationUnit:
case Decl::ExternCContext:
case Decl::Namespace:
case Decl::LinkageSpec:
case Decl::Export:
return nullptr;
// C/C++ tag types can only be defined in one place.
case Decl::Enum:
case Decl::Record:
if (const TagDecl *Def = cast<TagDecl>(DC)->getDefinition())
return Def;
return nullptr;
// FIXME: These can be defined in one place... except special member
// functions and out-of-line definitions.
case Decl::CXXRecord:
case Decl::ClassTemplateSpecialization:
case Decl::ClassTemplatePartialSpecialization:
return nullptr;
// Each function, method, and block declaration is its own DeclContext.
case Decl::Function:
case Decl::CXXMethod:
case Decl::CXXConstructor:
case Decl::CXXDestructor:
case Decl::CXXConversion:
case Decl::ObjCMethod:
case Decl::Block:
case Decl::OutlinedFunction:
case Decl::Captured:
// Objective C categories, category implementations, and class
// implementations can only be defined in one place.
case Decl::ObjCCategory:
case Decl::ObjCCategoryImpl:
case Decl::ObjCImplementation:
return DC;
case Decl::ObjCProtocol:
if (const ObjCProtocolDecl *Def
= cast<ObjCProtocolDecl>(DC)->getDefinition())
return Def;
return nullptr;
// FIXME: These are defined in one place, but properties in class extensions
// end up being back-patched into the main interface. See
// SemaObjC::HandlePropertyInClassExtension for the offending code.
case Decl::ObjCInterface:
return nullptr;
default:
llvm_unreachable("Unhandled DeclContext in AST reader");
}
llvm_unreachable("Unhandled decl kind");
}
bool serialization::isRedeclarableDeclKind(unsigned Kind) {
switch (static_cast<Decl::Kind>(Kind)) {
case Decl::TranslationUnit:
case Decl::ExternCContext:
// Special case of a "merged" declaration.
return true;
case Decl::Namespace:
case Decl::NamespaceAlias:
case Decl::Typedef:
case Decl::TypeAlias:
case Decl::Enum:
case Decl::Record:
case Decl::CXXRecord:
case Decl::ClassTemplateSpecialization:
case Decl::ClassTemplatePartialSpecialization:
case Decl::VarTemplateSpecialization:
case Decl::VarTemplatePartialSpecialization:
case Decl::Function:
case Decl::CXXDeductionGuide:
case Decl::CXXMethod:
case Decl::CXXConstructor:
case Decl::CXXDestructor:
case Decl::CXXConversion:
case Decl::UsingShadow:
case Decl::ConstructorUsingShadow:
case Decl::Var:
case Decl::FunctionTemplate:
case Decl::ClassTemplate:
case Decl::VarTemplate:
case Decl::TypeAliasTemplate:
case Decl::ObjCProtocol:
case Decl::ObjCInterface:
case Decl::Empty:
return true;
// Never redeclarable.
case Decl::ExplicitInstantiation:
case Decl::UsingDirective:
case Decl::Label:
case Decl::UnresolvedUsingTypename:
case Decl::TemplateTypeParm:
case Decl::EnumConstant:
case Decl::UnresolvedUsingValue:
case Decl::IndirectField:
case Decl::Field:
case Decl::MSProperty:
case Decl::MSGuid:
case Decl::UnnamedGlobalConstant:
case Decl::TemplateParamObject:
case Decl::ObjCIvar:
case Decl::ObjCAtDefsField:
case Decl::NonTypeTemplateParm:
case Decl::TemplateTemplateParm:
case Decl::Using:
case Decl::UsingEnum:
case Decl::UsingPack:
case Decl::ObjCMethod:
case Decl::ObjCCategory:
case Decl::ObjCCategoryImpl:
case Decl::ObjCImplementation:
case Decl::ObjCProperty:
case Decl::ObjCCompatibleAlias:
case Decl::LinkageSpec:
case Decl::Export:
case Decl::ObjCPropertyImpl:
case Decl::PragmaComment:
case Decl::PragmaDetectMismatch:
case Decl::FileScopeAsm:
case Decl::TopLevelStmt:
case Decl::AccessSpec:
case Decl::Friend:
case Decl::FriendTemplate:
case Decl::StaticAssert:
case Decl::Block:
case Decl::OutlinedFunction:
case Decl::Captured:
case Decl::Import:
case Decl::OMPThreadPrivate:
case Decl::OMPGroupPrivate:
case Decl::OMPAllocate:
case Decl::OMPRequires:
case Decl::OMPCapturedExpr:
case Decl::OMPDeclareReduction:
case Decl::OMPDeclareMapper:
case Decl::BuiltinTemplate:
case Decl::Decomposition:
case Decl::Binding:
case Decl::Concept:
case Decl::ImplicitConceptSpecialization:
case Decl::LifetimeExtendedTemporary:
case Decl::RequiresExprBody:
case Decl::UnresolvedUsingIfExists:
case Decl::HLSLBuffer:
case Decl::HLSLRootSignature:
case Decl::OpenACCDeclare:
case Decl::OpenACCRoutine:
case Decl::CXXExpansionStmt:
return false;
// These indirectly derive from Redeclarable<T> but are not actually
// redeclarable.
case Decl::ImplicitParam:
case Decl::ParmVar:
case Decl::ObjCTypeParam:
return false;
}
llvm_unreachable("Unhandled declaration kind");
}
bool serialization::needsAnonymousDeclarationNumber(const NamedDecl *D) {
// Friend declarations in dependent contexts aren't anonymous in the usual
// sense, but they cannot be found by name lookup in their semantic context
// (or indeed in any context), so we treat them as anonymous.
//
// This doesn't apply to friend tag decls; Sema makes those available to name
// lookup in the surrounding context.
if (D->getFriendObjectKind() &&
D->getLexicalDeclContext()->isDependentContext() && !isa<TagDecl>(D)) {
// For function templates and class templates, the template is numbered and
// not its pattern.
if (auto *FD = dyn_cast<FunctionDecl>(D))
return !FD->getDescribedFunctionTemplate();
if (auto *RD = dyn_cast<CXXRecordDecl>(D))
return !RD->getDescribedClassTemplate();
return true;
}
// At block scope, we number everything that we need to deduplicate, since we
// can't just use name matching to keep things lined up.
// FIXME: This is only necessary for an inline function or
// a template specialization or similar.
if (D->getLexicalDeclContext()->isFunctionOrMethod()) {
// An uninstantiated template pattern is never emitted; only its
// instantiations are numbered, so its decls need no cross-module number.
if (D->getLexicalDeclContext()->isDependentContext())
return false;
if (auto *VD = dyn_cast<VarDecl>(D))
return VD->isStaticLocal();
// FIXME: What about CapturedDecls (and declarations nested within them)?
return isa<TagDecl>(D);
}
// Otherwise, we only care about anonymous class members / block-scope decls.
// FIXME: We need to handle blocks within inline / templated variables too.
if (D->getDeclName())
return false;
if (!isa<RecordDecl, ObjCInterfaceDecl>(D->getLexicalDeclContext()))
return false;
return isa<TagDecl, FieldDecl>(D);
}