Compiling JUCE (develop) with clang-15 on Windows in C++20 mode results in the following warnings:
.../3rd_party/JUCE/modules/juce_core/containers/juce_Variant.cpp:496:43:
warning: out-of-line definition of constexpr static data member is redundant in C++17
and is deprecated [-Wdeprecated]
constexpr var::VariantType var::Instance::attributesVoid;
// Same warning for all attribute definitions (11)
// ...
Since the develop branch is on C++17 now, this should be an easy fix.