Incorrect "use 'template' keyword to treat 'xxx' as a dependent template name" inside of virtual member functions of template classes

[duncanhorn]

Bugzilla Link	39047
Version	7.0
OS	Windows NT
CC	@steveire

Extended Description

E.g. the following code fails to compile:

template <typename T>
struct special_ptr
{
    T* ptr;

    template <typename U>
    special_ptr<U> as()
    {
        special_ptr<U> result;
        result.ptr = reinterpret_cast<U*>(this->ptr);
        return result;
    }
};

template <typename T>
struct thing
{
    special_ptr<int> intPtr;

    virtual void do_something()
    {
        auto charPtr = this->intPtr.as<char>();
    }
};

struct empty {};

int main()
{
    thing<empty> t;
}

You can also view it at https://godbolt.org/z/ywb5CS. Note that GCC does not have a problem with it. If you change 'thing' to no longer be a class template or if you make 'do_something' no longer virtual, it compiles fine.

[steveire]

Seems related to #17775 though that (and its existing duplicate) does not require virtual as part of the repro.

[d-patyk]

Issue can't be reproduced with newest clang (check godbolt), should be closed

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (a06faff7-37e6-4b3d-a713-c8337ad9ce7f)

| | | | --- | --- | | Bugzilla Link | [39047](https://llvm.org/bz39047) | | Version | 7.0 | | OS | Windows NT | | CC | @steveire |

Extended Description

E.g. the following code fails to compile:

template <typename T>
struct special_ptr
{
    T* ptr;

    template <typename U>
    special_ptr<U> as()
    {
        special_ptr<U> result;
        result.ptr = reinterpret_cast<U*>(this->ptr);
        return result;
    }
};

template <typename T>
struct thing
{
    special_ptr<int> intPtr;

    virtual void do_something()
    {
        auto charPtr = this->intPtr.as<char>();
    }
};

struct empty {};

int main()
{
    thing<empty> t;
}

You can also view it at https://godbolt.org/z/ywb5CS. Note that GCC does not have a problem with it. If you change 'thing' to no longer be a class template or if you make 'do_something' no longer virtual, it compiles fine.