[Question]: Specialized template class parameter issue

[harsszegi]

Hi,
I have the following class:

#include
#include

template<typename DataType, typename Variant1, typename Variant2, typename Variant3>
class Foo
{
public:
Foo(const std::shared_ptr & foo) : foo_{foo} {}
Foo(const std::variant<Variant1, Variant2, Variant3> & bar) : bar_{bar} {}
private:
std::shared_ptr foo_;
std::variant<Variant1, Variant2, Variant3> bar_;
};

using FooInt = Foo<int, double, char, long>;

Even when I check FooInt's attribute, I fail to see for example shared_ptr's template parameter being "resolved" to DataType, instead I get (I guess the STL default) "_Ty" when I check the constructor arguments.

If I do an -ast-dump with clang-15 for example, I can clearly see though that even the unspecialized template class
definition contains the proper arguments for shared_ptr (I don't even see _Ty there), e.g.:

| | |-CXXConstructorDecl 0x56434eb1f3a8 <line:8:3, col:59> col:3 Foo<DataType, Variant1, Variant2, Variant3> 'void (const std::shared_ptr &)' implicit-inline
| | | |-ParmVarDecl 0x56434eb1f270 <col:7, col:41> col:41 referenced foo 'const std::shared_ptr &'
| | | |-CXXCtorInitializer Field 0x56434eb1fa00 'foo_' 'std::shared_ptr':'shared_ptr'
| | | | -InitListExpr 0x56434eb1fcc8 <col:52, col:56> 'void' | | | | -DeclRefExpr 0x56434eb1fca8 col:53 'const std::shared_ptr':'const shared_ptr' lvalue ParmVar 0x56434eb1f270 'foo' 'const std::shared_ptr &'
| | | `-CompoundStmt 0x56434eb1fd38 <col:58, col:59>

How should I / could I figure out that "_Ty" is actually "DataType" (same goes for std::variant's template parameters).
Thanks,