Wishlist for #[derive(MemSink, MemSource)]

[LukasKalbertodt]

Wishlist for #[derive(MemSink)]:

• Global cast mode instead of each field
• Name a field mesh (or so) but explicitly opt out of it being used (does not apply anymore)
• Modify finish() behavior: what is required and so on
• Specify cast mode without specifying what it's for: #[lox(cast = "lossy")]
• Specify how to deal with the alpha channel for colors (ignore additional, require one, ..)

Wishlist for #[derive(MemSource)]:

• ...