Context: Issue 20012 - export inside mixin doesn't seem to work
By parsing all .d files in all 1584 currently registered and available git repositories on Dub using libdparse, it was found that 13 packages have a LinkageAttribute inside a MixinTemplateDeclaration. The total number of mixin templates is 1497. Note: libdparse crashed on dmd's test suite, so dmd was skipped, but that shoudln't be important. Below is an overview for each package why extern() is used, with a link to one of the instances where it's used:
awebview: extern(C++) interfacing link
de_bindings: extern(C) only used for function pointer types link
derelict-glfw3: extern(C) only used for function pointer type aliases link
DPlug: extern(Windows) functions are override, can't be mixed in at global scope
link
Godot-D: uses pragma(mangle) to get proposed behavior link
Spasm: uses pragma(mangle) to get proposed behavior link
autowrap: mixes in static _py_init_impl, gets mangled correctly? link
HexChatD: uses pragma(mangle) to get proposed behavior link
dlangui: mixes in WinMain, should only be mixed in once link
mir-pybind: uses pragma(mangle) to get proposed behavior, but also defines rtAtExit multiple times. This would break. link
Reloaded: has __crash_return_handler function, only meant to be mixed in once
link
mir-pybuffer: uses pragma(mangle) to get proposed behavior link
erupted: extern(C) only used for function pointer type aliases link