syntax_data: {"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             // Don't pass the vtable, it's not an argument of the virtual fn.
context_before:         let layout = if is_virtual_call && arg_idx == Some(0) {
context_after:             // Instead, pass just the data pointer, but give it the type `*const/mut dyn Trait`