IDL 4.2 · §7.4.6

Forward declaration

A forward declaration names a struct, union or interface before its full definition, enabling mutually-recursive types. The parser tracks completion and rejects types left undefined at the end of the unit.

Example

struct Node;            // forward
struct Edge { Node from; Node to; };
struct Node { long id; };  // completed

ZeroDDS support

OMG IDL 4.2 section	§7.4.6
Implementation	`idl/src/ast`
Tests	`forward_decl_completion.rs`
Status	✓ RC3 — parsed, validated and code-generated across all target languages.

See also: IDL construct coverage · idl-4.2 audit · OMG IDL 4.2 spec