Attribute rustc_dump_vtable 

Dumps the virtual method table (“vtable”) of the annotated item.

See also the vtable_entries query.

See AttributeKind::RustcDumpVtable for the internal representation of this attribute.

Example

//@ dont-require-annotations: ERROR
//@ compile-flags: --crate-type lib -Z ui-testing=no

#![feature(rustc_attrs)]

#[rustc_dump_vtable]
type X = dyn Send;

#[rustc_dump_vtable]
type Y = dyn core::any::Any;

struct C;

#[rustc_dump_vtable]
impl Iterator for C {
    type Item = ();
    fn next(&mut self) -> Option<Self::Item> {
        Some(())
    }
}

produces:

error: vtable entries: [
          MetadataDropInPlace,
          MetadataSize,
          MetadataAlign,
      ]
--> $DIR/rustc_dump_vtable.rs:7:1
 |
7 | type X = dyn Send;
 | ^^^^^^

error: vtable entries: [
          MetadataDropInPlace,
          MetadataSize,
          MetadataAlign,
          Method(<dyn Any as Any>::type_id - shim(reify)),
      ]
 --> $DIR/rustc_dump_vtable.rs:10:1
  |
10 | type Y = dyn core::any::Any;
  | ^^^^^^

error: vtable entries: [
          MetadataDropInPlace,
          MetadataSize,
          MetadataAlign,
          Method(<C as Iterator>::next),
          Method(<C as Iterator>::size_hint),
          Method(<C as Iterator>::advance_by),
          Method(<C as Iterator>::nth),
      ]
 --> $DIR/rustc_dump_vtable.rs:15:1
  |
15 | impl Iterator for C {
  | ^^^^^^^^^^^^^^^^^^^

error: aborting due to 3 previous errors