#5600 Fix hidden member templates in derived classes

[Jonas Hahnfeld]

Fix hidden member templates in derived classes

According to Clang's interpretation of the C++ standard, "member
functions in the derived class override and/or hide member functions
with the same name and parameter types in a base class". This seems
to also hold for templated member functions and even if the code has
a using-declaration of the base class member.
This affects LilyPond's implementation of the method_finder template.
Luckily, the problem can be solved by just re-declaring the base
template specializations in each derived class instead of 'using' them.
The only drawback is that this doesn't work out-of-the-box for deeper
inheritance hierarchies. However, this only affects three ligature
engravers so I think it's worth the maintenance to just encode the
transitive inheritance manually.

http://codereview.appspot.com/559250043

[Jonas Hahnfeld]

For context, please see the following threads:
- https://lists.gnu.org/archive/html/lilypond-devel/2018-11/msg00019.html
- http://lists.llvm.org/pipermail/cfe-users/2018-November/001417.html
- https://bugs.llvm.org/show_bug.cgi?id=39581

[Anonymous]

Passes make. make check and a full make doc.

[Anonymous]

Patch on countdown for Nov 18th

[Jonas Hahnfeld]

Move comment that I overlooked

http://codereview.appspot.com/559250043

[Anonymous]

Patch counted down - please push.

[Jonas Hahnfeld]

Pushed as

commit 26b9b8e42a93b3b9a34effcfb61840d22ef9b272
Author: Jonas Hahnfeld <hahnjo@hahnjo.de>
Date:   Thu Nov 14 09:22:03 2019 +0100

    Issue 5600: Fix hidden member templates in derived classes

    According to Clang's interpretation of the C++ standard, "member
    functions in the derived class override and/or hide member functions
    with the same name and parameter types in a base class". This seems
    to also hold for templated member functions and even if the code has
    a using-declaration of the base class member.
    This affects LilyPond's implementation of the method_finder template.
    Luckily, the problem can be solved by just re-declaring the base
    template specializations in each derived class instead of 'using' them.
    The only drawback is that this doesn't work out-of-the-box for deeper
    inheritance hierarchies. However, this only affects three ligature
    engravers so I think it's worth the maintenance to just encode the
    transitive inheritance manually.