================
@@ -9895,26 +9895,30 @@ QualType
Sema::DeduceTemplateSpecializationFromInitializer(
if (!Template) {
if (auto *AliasTemplate = dyn_cast_or_null<TypeAliasTemplateDecl>(
TemplateName.getAsTemplateDecl())) {
- Diag(Kind.getLocation(),
- diag::warn_cxx17_compat_ctad_for_alias_templates);
- LookupTemplateDecl = AliasTemplate;
- auto UnderlyingType = AliasTemplate->getTemplatedDecl()
- ->getUnderlyingType()
- .getCanonicalType();
- // C++ [over.match.class.deduct#3]: ..., the defining-type-id of A must
be
- // of the form
- // [typename] [nested-name-specifier] [template] simple-template-id
- if (const auto *TST =
- UnderlyingType->getAs<TemplateSpecializationType>()) {
- Template = dyn_cast_or_null<ClassTemplateDecl>(
- TST->getTemplateName().getAsTemplateDecl());
- } else if (const auto *RT = UnderlyingType->getAs<RecordType>()) {
- // Cases where template arguments in the RHS of the alias are not
- // dependent. e.g.
- // using AliasFoo = Foo<bool>;
- if (const auto *CTSD = llvm::dyn_cast<ClassTemplateSpecializationDecl>(
- RT->getAsCXXRecordDecl()))
- Template = CTSD->getSpecializedTemplate();
+ if (getLangOpts().CPlusPlus20) {
+ LookupTemplateDecl = AliasTemplate;
+ auto UnderlyingType = AliasTemplate->getTemplatedDecl()
+ ->getUnderlyingType()
+ .getCanonicalType();
+ // C++ [over.match.class.deduct#3]: ..., the defining-type-id of A must
+ // be of the form
+ // [typename] [nested-name-specifier] [template] simple-template-id
+ if (const auto *TST =
+ UnderlyingType->getAs<TemplateSpecializationType>()) {
+ Template = dyn_cast_or_null<ClassTemplateDecl>(
+ TST->getTemplateName().getAsTemplateDecl());
+ } else if (const auto *RT = UnderlyingType->getAs<RecordType>()) {
+ // Cases where template arguments in the RHS of the alias are not
+ // dependent. e.g.
+ // using AliasFoo = Foo<bool>;
+ if (const auto *CTSD =
+ llvm::dyn_cast<ClassTemplateSpecializationDecl>(
+ RT->getAsCXXRecordDecl()))
+ Template = CTSD->getSpecializedTemplate();
+ }
+ } else {
+ Diag(Kind.getLocation(),
+ diag::warn_cxx17_compat_ctad_for_alias_templates);
----------------
mizvekov wrote:
This being still a warning is incompatible with the purpose of the change.
https://github.com/llvm/llvm-project/pull/133597
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