https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102228
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> --- I think there must be also a 1:1 correspondence to anon type and its single use FIELD_DECL thus building a back-chain via DECL_CONTEXT and a new ANON_AGGR_TYPE_FIELD should be possible. At least I failed to do sth like typedef struct { int i; } T; struct X { T; }; struct Y { T; }; aka use the same aggregate type anonymously from two contexts.