DR1315: a non-type template argument in a partial specialization is permitted
to make reference to template parameters. This is only a partial
implementation; we retain the restriction that the argument must not be
type-dependent, since it's unclear how that would work given the existence of
other language rules requiring an exact type match in this context, even for
type-dependent cases (a question has been raised on the core reflector).
llvm-svn: 290647
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 5a3083c..996a8ba 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1638,12 +1638,22 @@
typedef RecursiveASTVisitor<DependencyChecker> super;
unsigned Depth;
+
+ // Whether we're looking for a use of a template parameter that makes the
+ // overall construct type-dependent / a dependent type. This is strictly
+ // best-effort for now; we may fail to match at all for a dependent type
+ // in some cases if this is set.
+ bool IgnoreNonTypeDependent;
+
bool Match;
SourceLocation MatchLoc;
- DependencyChecker(unsigned Depth) : Depth(Depth), Match(false) {}
+ DependencyChecker(unsigned Depth, bool IgnoreNonTypeDependent)
+ : Depth(Depth), IgnoreNonTypeDependent(IgnoreNonTypeDependent),
+ Match(false) {}
- DependencyChecker(TemplateParameterList *Params) : Match(false) {
+ DependencyChecker(TemplateParameterList *Params, bool IgnoreNonTypeDependent)
+ : IgnoreNonTypeDependent(IgnoreNonTypeDependent), Match(false) {
NamedDecl *ND = Params->getParam(0);
if (TemplateTypeParmDecl *PD = dyn_cast<TemplateTypeParmDecl>(ND)) {
Depth = PD->getDepth();
@@ -1664,12 +1674,31 @@
return false;
}
+ bool TraverseStmt(Stmt *S, DataRecursionQueue *Q = nullptr) {
+ // Prune out non-type-dependent expressions if requested. This can
+ // sometimes result in us failing to find a template parameter reference
+ // (if a value-dependent expression creates a dependent type), but this
+ // mode is best-effort only.
+ if (auto *E = dyn_cast_or_null<Expr>(S))
+ if (IgnoreNonTypeDependent && !E->isTypeDependent())
+ return true;
+ return super::TraverseStmt(S, Q);
+ }
+
+ bool TraverseTypeLoc(TypeLoc TL) {
+ if (IgnoreNonTypeDependent && !TL.isNull() &&
+ !TL.getType()->isDependentType())
+ return true;
+ return super::TraverseTypeLoc(TL);
+ }
+
bool VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
return !Matches(TL.getTypePtr()->getDepth(), TL.getNameLoc());
}
bool VisitTemplateTypeParmType(const TemplateTypeParmType *T) {
- return !Matches(T->getDepth());
+ // For a best-effort search, keep looking until we find a location.
+ return IgnoreNonTypeDependent || !Matches(T->getDepth());
}
bool TraverseTemplateName(TemplateName N) {
@@ -1707,7 +1736,7 @@
/// list.
static bool
DependsOnTemplateParameters(QualType T, TemplateParameterList *Params) {
- DependencyChecker Checker(Params);
+ DependencyChecker Checker(Params, /*IgnoreNonTypeDependent*/false);
Checker.TraverseType(T);
return Checker.Match;
}
@@ -2539,10 +2568,6 @@
return CreateParsedType(Result, TLB.getTypeSourceInfo(Context, Result));
}
-static bool CheckTemplatePartialSpecializationArgs(
- Sema &S, SourceLocation NameLoc, TemplateParameterList *TemplateParams,
- unsigned ExplicitArgs, SmallVectorImpl<TemplateArgument> &TemplateArgs);
-
static bool CheckTemplateSpecializationScope(Sema &S, NamedDecl *Specialized,
NamedDecl *PrevDecl,
SourceLocation Loc,
@@ -2654,6 +2679,59 @@
S.Diag(Template->getLocation(), diag::note_template_decl_here);
}
+template<typename PartialSpecDecl>
+static void checkTemplatePartialSpecialization(Sema &S,
+ PartialSpecDecl *Partial) {
+ // C++1z [temp.class.spec]p8: (DR1495)
+ // - The specialization shall be more specialized than the primary
+ // template (14.5.5.2).
+ checkMoreSpecializedThanPrimary(S, Partial);
+
+ // C++ [temp.class.spec]p8: (DR1315)
+ // - Each template-parameter shall appear at least once in the
+ // template-id outside a non-deduced context.
+ // C++1z [temp.class.spec.match]p3 (P0127R2)
+ // If the template arguments of a partial specialization cannot be
+ // deduced because of the structure of its template-parameter-list
+ // and the template-id, the program is ill-formed.
+ auto *TemplateParams = Partial->getTemplateParameters();
+ llvm::SmallBitVector DeducibleParams(TemplateParams->size());
+ S.MarkUsedTemplateParameters(Partial->getTemplateArgs(), true,
+ TemplateParams->getDepth(), DeducibleParams);
+
+ if (!DeducibleParams.all()) {
+ unsigned NumNonDeducible = DeducibleParams.size() - DeducibleParams.count();
+ S.Diag(Partial->getLocation(), diag::ext_partial_specs_not_deducible)
+ << isa<VarTemplatePartialSpecializationDecl>(Partial)
+ << (NumNonDeducible > 1)
+ << SourceRange(Partial->getLocation(),
+ Partial->getTemplateArgsAsWritten()->RAngleLoc);
+ for (unsigned I = 0, N = DeducibleParams.size(); I != N; ++I) {
+ if (!DeducibleParams[I]) {
+ NamedDecl *Param = cast<NamedDecl>(TemplateParams->getParam(I));
+ if (Param->getDeclName())
+ S.Diag(Param->getLocation(),
+ diag::note_partial_spec_unused_parameter)
+ << Param->getDeclName();
+ else
+ S.Diag(Param->getLocation(),
+ diag::note_partial_spec_unused_parameter)
+ << "(anonymous)";
+ }
+ }
+ }
+}
+
+void Sema::CheckTemplatePartialSpecialization(
+ ClassTemplatePartialSpecializationDecl *Partial) {
+ checkTemplatePartialSpecialization(*this, Partial);
+}
+
+void Sema::CheckTemplatePartialSpecialization(
+ VarTemplatePartialSpecializationDecl *Partial) {
+ checkTemplatePartialSpecialization(*this, Partial);
+}
+
DeclResult Sema::ActOnVarTemplateSpecialization(
Scope *S, Declarator &D, TypeSourceInfo *DI, SourceLocation TemplateKWLoc,
TemplateParameterList *TemplateParams, StorageClass SC,
@@ -2703,11 +2781,12 @@
// Find the variable template (partial) specialization declaration that
// corresponds to these arguments.
if (IsPartialSpecialization) {
- if (CheckTemplatePartialSpecializationArgs(
- *this, TemplateNameLoc, VarTemplate->getTemplateParameters(),
- TemplateArgs.size(), Converted))
+ if (CheckTemplatePartialSpecializationArgs(TemplateNameLoc, VarTemplate,
+ TemplateArgs.size(), Converted))
return true;
+ // FIXME: Move these checks to CheckTemplatePartialSpecializationArgs so we
+ // also do them during instantiation.
bool InstantiationDependent;
if (!Name.isDependent() &&
!TemplateSpecializationType::anyDependentTemplateArguments(
@@ -2779,37 +2858,7 @@
if (PrevPartial && PrevPartial->getInstantiatedFromMember())
PrevPartial->setMemberSpecialization();
- // C++1z [temp.class.spec]p8: (DR1495)
- // - The specialization shall be more specialized than the primary
- // template (14.5.5.2).
- checkMoreSpecializedThanPrimary(*this, Partial);
-
- // Check that all of the template parameters of the variable template
- // partial specialization are deducible from the template
- // arguments. If not, this variable template partial specialization
- // will never be used.
- llvm::SmallBitVector DeducibleParams(TemplateParams->size());
- MarkUsedTemplateParameters(Partial->getTemplateArgs(), true,
- TemplateParams->getDepth(), DeducibleParams);
-
- if (!DeducibleParams.all()) {
- unsigned NumNonDeducible =
- DeducibleParams.size() - DeducibleParams.count();
- Diag(TemplateNameLoc, diag::warn_partial_specs_not_deducible)
- << /*variable template*/ 1 << (NumNonDeducible > 1)
- << SourceRange(TemplateNameLoc, RAngleLoc);
- for (unsigned I = 0, N = DeducibleParams.size(); I != N; ++I) {
- if (!DeducibleParams[I]) {
- NamedDecl *Param = cast<NamedDecl>(TemplateParams->getParam(I));
- if (Param->getDeclName())
- Diag(Param->getLocation(), diag::note_partial_spec_unused_parameter)
- << Param->getDeclName();
- else
- Diag(Param->getLocation(), diag::note_partial_spec_unused_parameter)
- << "(anonymous)";
- }
- }
- }
+ CheckTemplatePartialSpecialization(Partial);
} else {
// Create a new class template specialization declaration node for
// this explicit specialization or friend declaration.
@@ -6208,12 +6257,12 @@
return false;
}
-static SourceRange findTemplateParameter(unsigned Depth, Expr *E) {
- if (!E->isInstantiationDependent())
+static SourceRange findTemplateParameterInType(unsigned Depth, Expr *E) {
+ if (!E->isTypeDependent())
return SourceLocation();
- DependencyChecker Checker(Depth);
+ DependencyChecker Checker(Depth, /*IgnoreNonTypeDependent*/true);
Checker.TraverseStmt(E);
- if (Checker.Match && Checker.MatchLoc.isInvalid())
+ if (Checker.MatchLoc.isInvalid())
return E->getSourceRange();
return Checker.MatchLoc;
}
@@ -6221,9 +6270,9 @@
static SourceRange findTemplateParameter(unsigned Depth, TypeLoc TL) {
if (!TL.getType()->isDependentType())
return SourceLocation();
- DependencyChecker Checker(Depth);
+ DependencyChecker Checker(Depth, /*IgnoreNonTypeDependent*/true);
Checker.TraverseTypeLoc(TL);
- if (Checker.Match && Checker.MatchLoc.isInvalid())
+ if (Checker.MatchLoc.isInvalid())
return TL.getSourceRange();
return Checker.MatchLoc;
}
@@ -6275,8 +6324,16 @@
// shall not involve a template parameter of the partial
// specialization except when the argument expression is a
// simple identifier.
+ // -- The type of a template parameter corresponding to a
+ // specialized non-type argument shall not be dependent on a
+ // parameter of the specialization.
+ // DR1315 removes the first bullet, leaving an incoherent set of rules.
+ // We implement a compromise between the original rules and DR1315:
+ // -- A specialized non-type template argument shall not be
+ // type-dependent and the corresponding template parameter
+ // shall have a non-dependent type.
SourceRange ParamUseRange =
- findTemplateParameter(Param->getDepth(), ArgExpr);
+ findTemplateParameterInType(Param->getDepth(), ArgExpr);
if (ParamUseRange.isValid()) {
if (IsDefaultArgument) {
S.Diag(TemplateNameLoc,
@@ -6292,26 +6349,15 @@
return true;
}
- // -- The type of a template parameter corresponding to a
- // specialized non-type argument shall not be dependent on a
- // parameter of the specialization.
- //
- // FIXME: We need to delay this check until instantiation in some cases:
- //
- // template<template<typename> class X> struct A {
- // template<typename T, X<T> N> struct B;
- // template<typename T> struct B<T, 0>;
- // };
- // template<typename> using X = int;
- // A<X>::B<int, 0> b;
ParamUseRange = findTemplateParameter(
- Param->getDepth(), Param->getTypeSourceInfo()->getTypeLoc());
+ Param->getDepth(), Param->getTypeSourceInfo()->getTypeLoc());
if (ParamUseRange.isValid()) {
S.Diag(IsDefaultArgument ? TemplateNameLoc : ArgExpr->getLocStart(),
diag::err_dependent_typed_non_type_arg_in_partial_spec)
- << Param->getType() << ParamUseRange;
+ << Param->getType();
S.Diag(Param->getLocation(), diag::note_template_param_here)
- << (IsDefaultArgument ? ParamUseRange : SourceRange());
+ << (IsDefaultArgument ? ParamUseRange : SourceRange())
+ << ParamUseRange;
return true;
}
}
@@ -6330,20 +6376,25 @@
/// partial specialization.
///
/// \returns \c true if there was an error, \c false otherwise.
-static bool CheckTemplatePartialSpecializationArgs(
- Sema &S, SourceLocation TemplateNameLoc,
- TemplateParameterList *TemplateParams, unsigned NumExplicit,
- SmallVectorImpl<TemplateArgument> &TemplateArgs) {
- const TemplateArgument *ArgList = TemplateArgs.data();
+bool Sema::CheckTemplatePartialSpecializationArgs(
+ SourceLocation TemplateNameLoc, TemplateDecl *PrimaryTemplate,
+ unsigned NumExplicit, ArrayRef<TemplateArgument> TemplateArgs) {
+ // We have to be conservative when checking a template in a dependent
+ // context.
+ if (PrimaryTemplate->getDeclContext()->isDependentContext())
+ return false;
+ TemplateParameterList *TemplateParams =
+ PrimaryTemplate->getTemplateParameters();
for (unsigned I = 0, N = TemplateParams->size(); I != N; ++I) {
NonTypeTemplateParmDecl *Param
= dyn_cast<NonTypeTemplateParmDecl>(TemplateParams->getParam(I));
if (!Param)
continue;
- if (CheckNonTypeTemplatePartialSpecializationArgs(
- S, TemplateNameLoc, Param, &ArgList[I], 1, I >= NumExplicit))
+ if (CheckNonTypeTemplatePartialSpecializationArgs(*this, TemplateNameLoc,
+ Param, &TemplateArgs[I],
+ 1, I >= NumExplicit))
return true;
}
@@ -6487,11 +6538,12 @@
// Find the class template (partial) specialization declaration that
// corresponds to these arguments.
if (isPartialSpecialization) {
- if (CheckTemplatePartialSpecializationArgs(
- *this, TemplateNameLoc, ClassTemplate->getTemplateParameters(),
- TemplateArgs.size(), Converted))
+ if (CheckTemplatePartialSpecializationArgs(TemplateNameLoc, ClassTemplate,
+ TemplateArgs.size(), Converted))
return true;
+ // FIXME: Move this to CheckTemplatePartialSpecializationArgs so we
+ // also do it during instantiation.
bool InstantiationDependent;
if (!Name.isDependent() &&
!TemplateSpecializationType::anyDependentTemplateArguments(
@@ -6581,39 +6633,7 @@
if (PrevPartial && PrevPartial->getInstantiatedFromMember())
PrevPartial->setMemberSpecialization();
- // C++1z [temp.class.spec]p8: (DR1495)
- // - The specialization shall be more specialized than the primary
- // template (14.5.5.2).
- checkMoreSpecializedThanPrimary(*this, Partial);
-
- // Check that all of the template parameters of the class template
- // partial specialization are deducible from the template
- // arguments. If not, this class template partial specialization
- // will never be used.
- llvm::SmallBitVector DeducibleParams(TemplateParams->size());
- MarkUsedTemplateParameters(Partial->getTemplateArgs(), true,
- TemplateParams->getDepth(),
- DeducibleParams);
-
- if (!DeducibleParams.all()) {
- unsigned NumNonDeducible = DeducibleParams.size()-DeducibleParams.count();
- Diag(TemplateNameLoc, diag::warn_partial_specs_not_deducible)
- << /*class template*/0 << (NumNonDeducible > 1)
- << SourceRange(TemplateNameLoc, RAngleLoc);
- for (unsigned I = 0, N = DeducibleParams.size(); I != N; ++I) {
- if (!DeducibleParams[I]) {
- NamedDecl *Param = cast<NamedDecl>(TemplateParams->getParam(I));
- if (Param->getDeclName())
- Diag(Param->getLocation(),
- diag::note_partial_spec_unused_parameter)
- << Param->getDeclName();
- else
- Diag(Param->getLocation(),
- diag::note_partial_spec_unused_parameter)
- << "(anonymous)";
- }
- }
- }
+ CheckTemplatePartialSpecialization(Partial);
} else {
// Create a new class template specialization declaration node for
// this explicit specialization or friend declaration.
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index dbc322e..8e671ad 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3086,6 +3086,12 @@
Converted))
return nullptr;
+ // Check these arguments are valid for a template partial specialization.
+ if (SemaRef.CheckTemplatePartialSpecializationArgs(
+ PartialSpec->getLocation(), ClassTemplate, InstTemplateArgs.size(),
+ Converted))
+ return nullptr;
+
// Figure out where to insert this class template partial specialization
// in the member template's set of class template partial specializations.
void *InsertPos = nullptr;
@@ -3156,6 +3162,9 @@
InstPartialSpec->setInstantiatedFromMember(PartialSpec);
InstPartialSpec->setTypeAsWritten(WrittenTy);
+ // Check the completed partial specialization.
+ SemaRef.CheckTemplatePartialSpecialization(InstPartialSpec);
+
// Add this partial specialization to the set of class template partial
// specializations.
ClassTemplate->AddPartialSpecialization(InstPartialSpec,
@@ -3208,6 +3217,12 @@
InstTemplateArgs, false, Converted))
return nullptr;
+ // Check these arguments are valid for a template partial specialization.
+ if (SemaRef.CheckTemplatePartialSpecializationArgs(
+ PartialSpec->getLocation(), VarTemplate, InstTemplateArgs.size(),
+ Converted))
+ return nullptr;
+
// Figure out where to insert this variable template partial specialization
// in the member template's set of variable template partial specializations.
void *InsertPos = nullptr;
@@ -3282,6 +3297,9 @@
InstPartialSpec->setInstantiatedFromMember(PartialSpec);
InstPartialSpec->setTypeAsWritten(WrittenTy);
+ // Check the completed partial specialization.
+ SemaRef.CheckTemplatePartialSpecialization(InstPartialSpec);
+
// Add this partial specialization to the set of variable template partial
// specializations. The instantiation of the initializer is not necessary.
VarTemplate->AddPartialSpecialization(InstPartialSpec, /*InsertPos=*/nullptr);