syntax_data: {"ast_node_type":"other","tokens":[{"end":76,"kind":"keyword","start":0,"text":"assert!(layout.is_sized(),"}]}
source_snippet:     assert!(layout.is_sized(), "can't create a vtable for an unsized type");
context_before:         .expect("failed to build vtable representation");
context_after:     let size = layout.size.bytes();