http://llvm.org/bugs/show_bug.cgi?id=11848
Bug #: 11848
Summary: pack expansion of alias template with non-dependent
substitution fails
Product: clang
Version: unspecified
Platform: PC
OS/Version: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: C++0x
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
template<typename> using I = int;
template<typename T, typename...Ts>
int f(I<T> i, I<Ts> ...is) {
return i + f<Ts>(is...);
};
int k = f<char, double, float>(1, 2, 3);
This causes clang to assert:
src/tools/clang/lib/AST/ASTContext.cpp:2680: clang::QualType
clang::ASTContext::getPackExpansionType(clang::QualType,
llvm::Optional<unsigned int>): Assertion
`Pattern->containsUnexpandedParameterPack() && "Pack expansions must expand one
or more parameter packs"' failed.
The root cause here is presumably that the alias template contains an
unexpanded parameter pack, but its canonical type does not.
I'm not entirely sure whether this is supposed to be legal: on one hand, the
pattern clearly names a parameter pack, but on the other hand, an alias
template is supposed to be equivalent to its substitution, and its substitution
does not name a parameter pack.
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