[lldb] Detect when full DWARF debugging should be enabled

[augusto2112]

Automatically turn on full DWARF debugging if reflection metadata isn't available.

rdar://122711892

[augusto2112]

@swift-ci test

[adrian-prantl]

This pattern looks like it could be factored out into a template or a function that takes a std::function?

[augusto2112]

Maybe there's a better way to do this, but I think the "obvious" template solution is more trouble than it's worth. We'd need a templated function like:

  template <typename T>
  std::unique_ptr<T>
  getDescriptor(std::function<std::unique_ptr<T>()> descriptor_func) {
    if (m_descriptor_finder && shouldConsultDescriptorFinder())
      return descriptor_func();
    return nullptr;
  }

And then on the call side we'd need something like:

  std::unique_ptr<swift::reflection::BuiltinTypeDescriptorBase>
  getBuiltinTypeDescriptor(const swift::reflection::TypeRef *TR) override {
    std::function<
        std::unique_ptr<swift::reflection::BuiltinTypeDescriptorBase>()>
        lambda =
            [&]() { return m_descriptor_finder->getBuiltinTypeDescriptor(TR); };
    return getDescriptor(lambda);
  }

We need to spell out the lambda's type because the compiler is not able to deduce them.

[augusto2112]

@swift-ci test

[augusto2112]

@swift-ci test Windows

[augusto2112]

@swift-ci test windows