pl_lens
macro_rules! lens { #[proc_macro_hack] => { ... }; }
This is a macro-based shorthand that allows us to write:
lens!(SomeStruct.foo.bar_vec[3].baz)
instead of:
compose_lens!(SomeStructFooLens, FooBarVecLens, vec_lens::<BarThing>(3), BarThingBazLens)