{"ast_node_type":"other","tokens":[{"end":76,"kind":"keyword","start":0,"text":"source_projection:"}]}
             source_projection: ty::Binder<I, ty::ExistentialProjection<I>>,
            |ecx: &mut EvalCtxt<'_, D>,
             target_projection: ty::Binder<I, ty::ExistentialProjection<I>>| {