[cxx-interop] Do not import function templates with a parameter pack - #91410
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patrykstefanski wants to merge 1 commit into
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[cxx-interop] Do not import function templates with a parameter pack#91410patrykstefanski wants to merge 1 commit into
patrykstefanski wants to merge 1 commit into
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A pack `typename... Ts` is a clang::TemplateTypeParmDecl, so the
existing "all template parameters must be template type parameters"
guard in VisitFunctionTemplateDecl let it through. The pack collapsed
into a single ordinary generic parameter and the pack expansion
parameter was imported as Any:
func parameterPack<Ts>(_ ts: Any, Ts: Ts.Type)
Calling that from Swift triggers an assertion in getPackAsArray().
Bail on packs instead, the way non-type template parameters are already
treated, so a call site gets "cannot find 'parameterPack' in scope"
rather than an assertion failure.
rdar://184658782
patrykstefanski
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Xazax-hun,
beccadax,
egorzhdan,
hamishknight,
hborla,
hnrklssn,
ian-twilightcoder,
j-hui,
slavapestov,
susmonteiro and
xedin
as code owners
August 11, 2026 23:27
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Author
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@swift-ci please test |
Xazax-hun
approved these changes
Aug 12, 2026
egorzhdan
approved these changes
Aug 12, 2026
Comment on lines
+5015
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| const auto *typeParam = | ||
| dyn_cast<clang::TemplateTypeParmDecl>(param); | ||
| return typeParam && !typeParam->isParameterPack(); |
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We could probably hoist this check into importNameImpl and save some cycles on name lookup. I don't think this is very important though.
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A pack
typename... Tsis a clang::TemplateTypeParmDecl, so the existing "all template parameters must be template type parameters" guard in VisitFunctionTemplateDecl let it through. The pack collapsed into a single ordinary generic parameter and the pack expansion parameter was imported as Any:Calling that from Swift triggers an assertion in getPackAsArray().
Bail on packs instead, the way non-type template parameters are already treated, so a call site gets "cannot find 'parameterPack' in scope" rather than an assertion failure.
rdar://184658782