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[Clang][AST] Track whether template template parameters used the 'typename' keyword #88139

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Apr 11, 2024
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[Clang][AST] Track whether template template parameters used the 'typename' keyword #88139

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[Clang][AST] Track whether template template parameters used the 'typ…
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4 changes: 4 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -360,6 +360,9 @@ Improvements to Clang's diagnostics
Added the ``-Wtentative-definition-array`` warning group to cover this.
Fixes #GH87766

- Clang now uses the correct type-parameter-key (``class`` or ``typename``) when printing
template template parameter declarations.

Improvements to Clang's time-trace
----------------------------------

Expand Down Expand Up @@ -535,6 +538,7 @@ Bug Fixes to C++ Support
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
- Clang now properly preserves ``FoundDecls`` within a ``ConceptReference``. (#GH82628)
- The presence of the ``typename`` keyword is now stored in ``TemplateTemplateParmDecl``.

Miscellaneous Bug Fixes
^^^^^^^^^^^^^^^^^^^^^^^
Expand Down
49 changes: 33 additions & 16 deletions clang/include/clang/AST/DeclTemplate.h
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Expand Up @@ -1581,26 +1581,36 @@ class TemplateTemplateParmDecl final
DefaultArgStorage<TemplateTemplateParmDecl, TemplateArgumentLoc *>;
DefArgStorage DefaultArgument;

/// Whether this template template parameter was declaration with
/// the 'typename' keyword.
///
/// If false, it was declared with the 'class' keyword.
LLVM_PREFERRED_TYPE(bool)
unsigned Typename : 1;

/// Whether this parameter is a parameter pack.
bool ParameterPack;
LLVM_PREFERRED_TYPE(bool)
unsigned ParameterPack : 1;

/// Whether this template template parameter is an "expanded"
/// parameter pack, meaning that it is a pack expansion and we
/// already know the set of template parameters that expansion expands to.
bool ExpandedParameterPack = false;
LLVM_PREFERRED_TYPE(bool)
unsigned ExpandedParameterPack : 1;

/// The number of parameters in an expanded parameter pack.
unsigned NumExpandedParams = 0;

TemplateTemplateParmDecl(DeclContext *DC, SourceLocation L,
unsigned D, unsigned P, bool ParameterPack,
IdentifierInfo *Id, TemplateParameterList *Params)
TemplateTemplateParmDecl(DeclContext *DC, SourceLocation L, unsigned D,
unsigned P, bool ParameterPack, IdentifierInfo *Id,
bool Typename, TemplateParameterList *Params)
: TemplateDecl(TemplateTemplateParm, DC, L, Id, Params),
TemplateParmPosition(D, P), ParameterPack(ParameterPack) {}
TemplateParmPosition(D, P), Typename(Typename),
ParameterPack(ParameterPack), ExpandedParameterPack(false) {}

TemplateTemplateParmDecl(DeclContext *DC, SourceLocation L,
unsigned D, unsigned P,
IdentifierInfo *Id, TemplateParameterList *Params,
TemplateTemplateParmDecl(DeclContext *DC, SourceLocation L, unsigned D,
unsigned P, IdentifierInfo *Id, bool Typename,
TemplateParameterList *Params,
ArrayRef<TemplateParameterList *> Expansions);

void anchor() override;
Expand All @@ -1613,14 +1623,13 @@ class TemplateTemplateParmDecl final
static TemplateTemplateParmDecl *Create(const ASTContext &C, DeclContext *DC,
SourceLocation L, unsigned D,
unsigned P, bool ParameterPack,
IdentifierInfo *Id,
IdentifierInfo *Id, bool Typename,
TemplateParameterList *Params);
static TemplateTemplateParmDecl *Create(const ASTContext &C, DeclContext *DC,
SourceLocation L, unsigned D,
unsigned P,
IdentifierInfo *Id,
TemplateParameterList *Params,
ArrayRef<TemplateParameterList *> Expansions);
static TemplateTemplateParmDecl *
Create(const ASTContext &C, DeclContext *DC, SourceLocation L, unsigned D,
unsigned P, IdentifierInfo *Id, bool Typename,
TemplateParameterList *Params,
ArrayRef<TemplateParameterList *> Expansions);

static TemplateTemplateParmDecl *CreateDeserialized(ASTContext &C,
unsigned ID);
Expand All @@ -1634,6 +1643,14 @@ class TemplateTemplateParmDecl final
using TemplateParmPosition::setPosition;
using TemplateParmPosition::getIndex;

/// Whether this template template parameter was declared with
/// the 'typename' keyword.
bool wasDeclaredWithTypename() const { return Typename; }
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So these should return the syntax of typename and class rather than a bool.

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We do not have an enum for that yet afaik (ie this is consistent with ActOnTypeParameter).
I would not oppose using an enum everywhere


/// Set whether this template template parameter was declared with
/// the 'typename' or 'class' keyword.
void setDeclaredWithTypename(bool withTypename) { Typename = withTypename; }

/// Whether this template template parameter is a template
/// parameter pack.
///
Expand Down
2 changes: 1 addition & 1 deletion clang/include/clang/Sema/Sema.h
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Expand Up @@ -9064,7 +9064,7 @@ class Sema final : public SemaBase {
Expr *DefaultArg);
NamedDecl *ActOnTemplateTemplateParameter(
Scope *S, SourceLocation TmpLoc, TemplateParameterList *Params,
SourceLocation EllipsisLoc, IdentifierInfo *ParamName,
bool Typename, SourceLocation EllipsisLoc, IdentifierInfo *ParamName,
SourceLocation ParamNameLoc, unsigned Depth, unsigned Position,
SourceLocation EqualLoc, ParsedTemplateArgument DefaultArg);

Expand Down
2 changes: 1 addition & 1 deletion clang/lib/AST/ASTContext.cpp
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Expand Up @@ -799,7 +799,7 @@ ASTContext::getCanonicalTemplateTemplateParmDecl(

TemplateTemplateParmDecl *CanonTTP = TemplateTemplateParmDecl::Create(
*this, getTranslationUnitDecl(), SourceLocation(), TTP->getDepth(),
TTP->getPosition(), TTP->isParameterPack(), nullptr,
TTP->getPosition(), TTP->isParameterPack(), nullptr, /*Typename=*/false,
TemplateParameterList::Create(*this, SourceLocation(), SourceLocation(),
CanonParams, SourceLocation(),
/*RequiresClause=*/nullptr));
Expand Down
3 changes: 2 additions & 1 deletion clang/lib/AST/ASTImporter.cpp
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Expand Up @@ -5952,7 +5952,8 @@ ASTNodeImporter::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
ToD, D, Importer.getToContext(),
Importer.getToContext().getTranslationUnitDecl(), *LocationOrErr,
D->getDepth(), D->getPosition(), D->isParameterPack(),
(*NameOrErr).getAsIdentifierInfo(), *TemplateParamsOrErr))
(*NameOrErr).getAsIdentifierInfo(), D->wasDeclaredWithTypename(),
*TemplateParamsOrErr))
return ToD;

if (D->hasDefaultArgument()) {
Expand Down
5 changes: 4 additions & 1 deletion clang/lib/AST/DeclPrinter.cpp
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Expand Up @@ -1218,7 +1218,10 @@ void DeclPrinter::VisitTemplateDecl(const TemplateDecl *D) {

if (const TemplateTemplateParmDecl *TTP =
dyn_cast<TemplateTemplateParmDecl>(D)) {
Out << "class";
if (TTP->wasDeclaredWithTypename())
Out << "typename";
else
Out << "class";

if (TTP->isParameterPack())
Out << " ...";
Expand Down
18 changes: 9 additions & 9 deletions clang/lib/AST/DeclTemplate.cpp
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Expand Up @@ -805,10 +805,10 @@ void TemplateTemplateParmDecl::anchor() {}

TemplateTemplateParmDecl::TemplateTemplateParmDecl(
DeclContext *DC, SourceLocation L, unsigned D, unsigned P,
IdentifierInfo *Id, TemplateParameterList *Params,
IdentifierInfo *Id, bool Typename, TemplateParameterList *Params,
ArrayRef<TemplateParameterList *> Expansions)
: TemplateDecl(TemplateTemplateParm, DC, L, Id, Params),
TemplateParmPosition(D, P), ParameterPack(true),
TemplateParmPosition(D, P), Typename(Typename), ParameterPack(true),
ExpandedParameterPack(true), NumExpandedParams(Expansions.size()) {
if (!Expansions.empty())
std::uninitialized_copy(Expansions.begin(), Expansions.end(),
Expand All @@ -819,26 +819,26 @@ TemplateTemplateParmDecl *
TemplateTemplateParmDecl::Create(const ASTContext &C, DeclContext *DC,
SourceLocation L, unsigned D, unsigned P,
bool ParameterPack, IdentifierInfo *Id,
TemplateParameterList *Params) {
bool Typename, TemplateParameterList *Params) {
return new (C, DC) TemplateTemplateParmDecl(DC, L, D, P, ParameterPack, Id,
Params);
Typename, Params);
}

TemplateTemplateParmDecl *
TemplateTemplateParmDecl::Create(const ASTContext &C, DeclContext *DC,
SourceLocation L, unsigned D, unsigned P,
IdentifierInfo *Id,
IdentifierInfo *Id, bool Typename,
TemplateParameterList *Params,
ArrayRef<TemplateParameterList *> Expansions) {
return new (C, DC,
additionalSizeToAlloc<TemplateParameterList *>(Expansions.size()))
TemplateTemplateParmDecl(DC, L, D, P, Id, Params, Expansions);
TemplateTemplateParmDecl(DC, L, D, P, Id, Typename, Params, Expansions);
}

TemplateTemplateParmDecl *
TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
return new (C, ID) TemplateTemplateParmDecl(nullptr, SourceLocation(), 0, 0,
false, nullptr, nullptr);
false, nullptr, false, nullptr);
}

TemplateTemplateParmDecl *
Expand All @@ -847,7 +847,7 @@ TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, unsigned ID,
auto *TTP =
new (C, ID, additionalSizeToAlloc<TemplateParameterList *>(NumExpansions))
TemplateTemplateParmDecl(nullptr, SourceLocation(), 0, 0, nullptr,
nullptr, std::nullopt);
false, nullptr, std::nullopt);
TTP->NumExpandedParams = NumExpansions;
return TTP;
}
Expand Down Expand Up @@ -1469,7 +1469,7 @@ createMakeIntegerSeqParameterList(const ASTContext &C, DeclContext *DC) {
// template <typename T, ...Ints> class IntSeq
auto *TemplateTemplateParm = TemplateTemplateParmDecl::Create(
C, DC, SourceLocation(), /*Depth=*/0, /*Position=*/0,
/*ParameterPack=*/false, /*Id=*/nullptr, TPL);
/*ParameterPack=*/false, /*Id=*/nullptr, /*Typename=*/false, TPL);
TemplateTemplateParm->setImplicit(true);

// typename T
Expand Down
9 changes: 5 additions & 4 deletions clang/lib/Parse/ParseTemplate.cpp
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Expand Up @@ -805,10 +805,12 @@ NamedDecl *Parser::ParseTemplateTemplateParameter(unsigned Depth,
// identifier, comma, or greater. Provide a fixit if the identifier, comma,
// or greater appear immediately or after 'struct'. In the latter case,
// replace the keyword with 'class'.
bool TypenameKeyword = false;
if (!TryConsumeToken(tok::kw_class)) {
bool Replace = Tok.isOneOf(tok::kw_typename, tok::kw_struct);
const Token &Next = Tok.is(tok::kw_struct) ? NextToken() : Tok;
if (Tok.is(tok::kw_typename)) {
TypenameKeyword = true;
Diag(Tok.getLocation(),
getLangOpts().CPlusPlus17
? diag::warn_cxx14_compat_template_template_param_typename
Expand Down Expand Up @@ -878,10 +880,9 @@ NamedDecl *Parser::ParseTemplateTemplateParameter(unsigned Depth,
}
}

return Actions.ActOnTemplateTemplateParameter(getCurScope(), TemplateLoc,
ParamList, EllipsisLoc,
ParamName, NameLoc, Depth,
Position, EqualLoc, DefaultArg);
return Actions.ActOnTemplateTemplateParameter(
getCurScope(), TemplateLoc, ParamList, TypenameKeyword, EllipsisLoc,
ParamName, NameLoc, Depth, Position, EqualLoc, DefaultArg);
}

/// ParseNonTypeTemplateParameter - Handle the parsing of non-type
Expand Down
24 changes: 9 additions & 15 deletions clang/lib/Sema/SemaTemplate.cpp
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Expand Up @@ -1630,26 +1630,20 @@ NamedDecl *Sema::ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
/// ActOnTemplateTemplateParameter - Called when a C++ template template
/// parameter (e.g. T in template <template \<typename> class T> class array)
/// has been parsed. S is the current scope.
NamedDecl *Sema::ActOnTemplateTemplateParameter(Scope* S,
SourceLocation TmpLoc,
TemplateParameterList *Params,
SourceLocation EllipsisLoc,
IdentifierInfo *Name,
SourceLocation NameLoc,
unsigned Depth,
unsigned Position,
SourceLocation EqualLoc,
ParsedTemplateArgument Default) {
NamedDecl *Sema::ActOnTemplateTemplateParameter(
Scope *S, SourceLocation TmpLoc, TemplateParameterList *Params,
bool Typename, SourceLocation EllipsisLoc, IdentifierInfo *Name,
SourceLocation NameLoc, unsigned Depth, unsigned Position,
SourceLocation EqualLoc, ParsedTemplateArgument Default) {
assert(S->isTemplateParamScope() &&
"Template template parameter not in template parameter scope!");

// Construct the parameter object.
bool IsParameterPack = EllipsisLoc.isValid();
TemplateTemplateParmDecl *Param =
TemplateTemplateParmDecl::Create(Context, Context.getTranslationUnitDecl(),
NameLoc.isInvalid()? TmpLoc : NameLoc,
Depth, Position, IsParameterPack,
Name, Params);
TemplateTemplateParmDecl *Param = TemplateTemplateParmDecl::Create(
Context, Context.getTranslationUnitDecl(),
NameLoc.isInvalid() ? TmpLoc : NameLoc, Depth, Position, IsParameterPack,
Name, Typename, Params);
Param->setAccess(AS_public);

if (Param->isParameterPack())
Expand Down
6 changes: 4 additions & 2 deletions clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
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Expand Up @@ -3233,12 +3233,14 @@ TemplateDeclInstantiator::VisitTemplateTemplateParmDecl(
Param = TemplateTemplateParmDecl::Create(
SemaRef.Context, Owner, D->getLocation(),
D->getDepth() - TemplateArgs.getNumSubstitutedLevels(),
D->getPosition(), D->getIdentifier(), InstParams, ExpandedParams);
D->getPosition(), D->getIdentifier(), D->wasDeclaredWithTypename(),
InstParams, ExpandedParams);
else
Param = TemplateTemplateParmDecl::Create(
SemaRef.Context, Owner, D->getLocation(),
D->getDepth() - TemplateArgs.getNumSubstitutedLevels(),
D->getPosition(), D->isParameterPack(), D->getIdentifier(), InstParams);
D->getPosition(), D->isParameterPack(), D->getIdentifier(),
D->wasDeclaredWithTypename(), InstParams);
if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited()) {
NestedNameSpecifierLoc QualifierLoc =
D->getDefaultArgument().getTemplateQualifierLoc();
Expand Down
1 change: 1 addition & 0 deletions clang/lib/Serialization/ASTReaderDecl.cpp
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Expand Up @@ -2715,6 +2715,7 @@ void ASTDeclReader::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {

void ASTDeclReader::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
VisitTemplateDecl(D);
D->setDeclaredWithTypename(Record.readBool());
// TemplateParmPosition.
D->setDepth(Record.readInt());
D->setPosition(Record.readInt());
Expand Down
1 change: 1 addition & 0 deletions clang/lib/Serialization/ASTWriterDecl.cpp
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Expand Up @@ -1921,6 +1921,7 @@ void ASTDeclWriter::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
Record.push_back(D->getNumExpansionTemplateParameters());

VisitTemplateDecl(D);
Record.push_back(D->wasDeclaredWithTypename());
// TemplateParmPosition.
Record.push_back(D->getDepth());
Record.push_back(D->getPosition());
Expand Down
3 changes: 1 addition & 2 deletions clang/unittests/AST/DeclPrinterTest.cpp
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Expand Up @@ -1220,8 +1220,7 @@ TEST(DeclPrinter, TestTemplateTemplateParameterWrittenWithTypename) {
ASSERT_TRUE(PrintedDeclCXX17Matches(
"template <template <typename> typename Z> void A();",
functionTemplateDecl(hasName("A")).bind("id"),
"template <template <typename> class Z> void A()"));
// WRONG: We should use typename if the parameter was written with it.
"template <template <typename> typename Z> void A()"));
}

TEST(DeclPrinter, TestTemplateArgumentList1) {
Expand Down