clang triggers an "UNREACHABLE executed" assertion (somehow related to typename)

This test program shows the assertion on Godbolt: https://godbolt.org/z/Md3vhYx1j

```cpp
#include

template
class Presets final
{
public:
using PresetMapping=T;
};

class Class
{
public:
template
void updatePresets(Presets::PresetMapping& p_presets);
template
Presets::PresetMapping::value_type getVisiblePreset();
};

template
void Class::updatePresets(Presets::PresetMapping& /*p_presets*/)
{
[[maybe_unused]] const typename Presets::PresetMapping::value_type visiblePreset = getVisiblePreset();
}

template
Presets::PresetMapping::value_type Class::getVisiblePreset()
{
return {};
}

int main()
{
Presets::PresetMapping presetMapping;
Class().updatePresets(presetMapping);
return 0;
}

```

Interestingly, the assertion vanishes if two "typename" keywords are added in lines 16 and 26: https://godbolt.org/z/Kza9z5eYn

This was actually how I found the issue. clang-tidy check readability-redundant-typename reported the two "typename" keywords to be unnecessary. However after their removal the assertion occurred.

MSVC 17.14 (VS 2022) compiles the code with and without the "typename" keyword.