Stable type identifiers: a missing piece for crABI and export

The idea has evolved over the course of this thread. The initial post mentioned dynamic linkage as the motivation, but in post #14 I explicitly distinguished between two separate issues: identifiers linked to ABI compatibility, which is what #3435 addresses, and stable type identification independent of the ABI. My question since post #14 specifically concerns the second case. Is there any prior work on this?