[Clang][Sema] Diagnose unexpanded packs in the template argument lists of function template specializations #76677
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@llvm/pr-subscribers-clang Author: Krystian Stasiowski (sdkrystian) ChangesThis diagnoses unexpanded packs in the unqualified-id of a function template specialization's declarator-id, e.g.: template<typename... Ts>
struct A
{
template<typename U>
void f();
template<>
void f<Ts>(); // error: explicit specialization contains unexpanded parameter pack 'Ts'
};I moved the handling of template-id's so it happens right after we determine whether we are declaring a function template/function template specialization so diagnostics are issued in lexical order. Full diff: https://github.com/llvm/llvm-project/pull/76677.diff 2 Files Affected:
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index ffbe317d559995..e94637b4f053e0 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -9900,15 +9900,15 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
// Match up the template parameter lists with the scope specifier, then
// determine whether we have a template or a template specialization.
bool Invalid = false;
+ TemplateIdAnnotation *TemplateId =
+ D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId
+ ? D.getName().TemplateId
+ : nullptr;
TemplateParameterList *TemplateParams =
MatchTemplateParametersToScopeSpecifier(
D.getDeclSpec().getBeginLoc(), D.getIdentifierLoc(),
- D.getCXXScopeSpec(),
- D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId
- ? D.getName().TemplateId
- : nullptr,
- TemplateParamLists, isFriend, isMemberSpecialization,
- Invalid);
+ D.getCXXScopeSpec(), TemplateId, TemplateParamLists, isFriend,
+ isMemberSpecialization, Invalid);
if (TemplateParams) {
// Check that we can declare a template here.
if (CheckTemplateDeclScope(S, TemplateParams))
@@ -9921,6 +9921,11 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
if (Name.getNameKind() == DeclarationName::CXXDestructorName) {
Diag(NewFD->getLocation(), diag::err_destructor_template);
NewFD->setInvalidDecl();
+ // Function template with explicit template arguments.
+ } else if (TemplateId) {
+ Diag(D.getIdentifierLoc(), diag::err_function_template_partial_spec)
+ << SourceRange(TemplateId->LAngleLoc, TemplateId->RAngleLoc);
+ NewFD->setInvalidDecl();
}
// If we're adding a template to a dependent context, we may need to
@@ -9973,6 +9978,11 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
<< FixItHint::CreateRemoval(RemoveRange)
<< FixItHint::CreateInsertion(InsertLoc, "<>");
Invalid = true;
+
+ // Recover by faking up an empty template argument list.
+ HasExplicitTemplateArgs = true;
+ TemplateArgs.setLAngleLoc(InsertLoc);
+ TemplateArgs.setRAngleLoc(InsertLoc);
}
}
} else {
@@ -9986,6 +9996,33 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
if (TemplateParamLists.size() > 0)
// For source fidelity, store all the template param lists.
NewFD->setTemplateParameterListsInfo(Context, TemplateParamLists);
+
+ // "friend void foo<>(int);" is an implicit specialization decl.
+ if (isFriend && TemplateId)
+ isFunctionTemplateSpecialization = true;
+ }
+
+ // If this is a function template specialization and the unqualified-id of
+ // the declarator-id is a template-id, convert the template argument list
+ // into our AST format and check for unexpanded packs.
+ if (isFunctionTemplateSpecialization && TemplateId) {
+ HasExplicitTemplateArgs = true;
+
+ TemplateArgs.setLAngleLoc(TemplateId->LAngleLoc);
+ TemplateArgs.setRAngleLoc(TemplateId->RAngleLoc);
+ ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
+ TemplateId->NumArgs);
+ translateTemplateArguments(TemplateArgsPtr, TemplateArgs);
+
+ // FIXME: Should we check for unexpanded packs if this was an (invalid)
+ // declaration of a function template partial specialization? Should we
+ // consider the unexpanded pack context to be a partial specialization?
+ for (const TemplateArgumentLoc &ArgLoc : TemplateArgs.arguments()) {
+ if (DiagnoseUnexpandedParameterPack(
+ ArgLoc, isFriend ? UPPC_FriendDeclaration
+ : UPPC_ExplicitSpecialization))
+ NewFD->setInvalidDecl();
+ }
}
if (Invalid) {
@@ -10438,46 +10475,6 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
diag::ext_operator_new_delete_declared_inline)
<< NewFD->getDeclName();
- // If the declarator is a template-id, translate the parser's template
- // argument list into our AST format.
- if (D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId) {
- TemplateIdAnnotation *TemplateId = D.getName().TemplateId;
- TemplateArgs.setLAngleLoc(TemplateId->LAngleLoc);
- TemplateArgs.setRAngleLoc(TemplateId->RAngleLoc);
- ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
- TemplateId->NumArgs);
- translateTemplateArguments(TemplateArgsPtr,
- TemplateArgs);
-
- HasExplicitTemplateArgs = true;
-
- if (NewFD->isInvalidDecl()) {
- HasExplicitTemplateArgs = false;
- } else if (FunctionTemplate) {
- // Function template with explicit template arguments.
- Diag(D.getIdentifierLoc(), diag::err_function_template_partial_spec)
- << SourceRange(TemplateId->LAngleLoc, TemplateId->RAngleLoc);
-
- HasExplicitTemplateArgs = false;
- } else if (isFriend) {
- // "friend void foo<>(int);" is an implicit specialization decl.
- isFunctionTemplateSpecialization = true;
- } else {
- assert(isFunctionTemplateSpecialization &&
- "should have a 'template<>' for this decl");
- }
- } else if (isFriend && isFunctionTemplateSpecialization) {
- // This combination is only possible in a recovery case; the user
- // wrote something like:
- // template <> friend void foo(int);
- // which we're recovering from as if the user had written:
- // friend void foo<>(int);
- // Go ahead and fake up a template id.
- HasExplicitTemplateArgs = true;
- TemplateArgs.setLAngleLoc(D.getIdentifierLoc());
- TemplateArgs.setRAngleLoc(D.getIdentifierLoc());
- }
-
// We do not add HD attributes to specializations here because
// they may have different constexpr-ness compared to their
// templates and, after maybeAddCUDAHostDeviceAttrs() is applied,
diff --git a/clang/test/CXX/temp/temp.decls/temp.variadic/p5.cpp b/clang/test/CXX/temp/temp.decls/temp.variadic/p5.cpp
index 30ce6b40e1fb5f..3c500c2c4dc4a7 100644
--- a/clang/test/CXX/temp/temp.decls/temp.variadic/p5.cpp
+++ b/clang/test/CXX/temp/temp.decls/temp.variadic/p5.cpp
@@ -376,6 +376,11 @@ namespace Specializations {
template<typename... Ts>
struct PrimaryClass<Ts>; // expected-error{{partial specialization contains unexpanded parameter pack 'Ts'}}
+ template<typename T, typename... Ts>
+ void PrimaryFunction();
+ template<typename T, typename... Ts>
+ void PrimaryFunction<Ts>(); // expected-error{{function template partial specialization is not allowed}}
+
#if __cplusplus >= 201402L
template<typename T, typename... Ts>
constexpr int PrimaryVar = 0;
@@ -392,6 +397,13 @@ namespace Specializations {
template<typename U>
struct InnerClass<U, Ts>; // expected-error{{partial specialization contains unexpanded parameter pack 'Ts'}}
+ template<typename... Us>
+ void InnerFunction();
+ template<>
+ void InnerFunction<Ts>(); // expected-error{{explicit specialization contains unexpanded parameter pack 'Ts'}}
+
+ friend void PrimaryFunction<Ts>(); // expected-error{{friend declaration contains unexpanded parameter pack 'Ts'}}
+
#if __cplusplus >= 201402L
template<typename... Us>
constexpr static int InnerVar = 0;
|
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Ping @erichkeane |
|
Can you add a release note? |
erichkeane
reviewed
Jan 3, 2024
…s of function template specializations
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erichkeane
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Jan 3, 2024
| @@ -518,6 +518,7 @@ Improvements to Clang's diagnostics | |||
| - Clang now diagnoses definitions of friend function specializations, e.g. ``friend void f<>(int) {}``. | |||
| - Clang now diagnoses narrowing conversions involving const references. | |||
| (`#63151: <https://github.com/llvm/llvm-project/issues/63151>`_). | |||
| - Clang now diagnoses unexpanded packs within the template argument lists of function template specializations. | |||
There was a problem hiding this comment.
Do you have a github issue that this fixes, or is this just something that never had an issue? If it has one, please include here, else, this is fine.
There was a problem hiding this comment.
@erichkeane I just looked -- I don't see an open issue.
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Added release note & rebased. I'll need someone to merge this for me :) |
|
This broke check-clang-tools: http://45.33.8.238/linux/127018/step_8.txt Please take a look and revert for now if it takes a while to fix. |
|
Reverted here: #76876 @sdkrystian : please take a look at the regression that nico pointed out and re-submit with considerations for that. |
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This diagnoses unexpanded packs in the unqualified-id of a function template specialization's declarator-id. For example:
I moved the handling of template-id's so it happens right after we determine whether we are declaring a function template/function template specialization so diagnostics are issued in lexical order.