[gpm]

And in the rare instances where you're using in-development features "rust nightly-2023-12-18"

Literally the only reason to specify via a hash* would be if you were using such a bleeding edge feature that it was only merged in the last 48 hours or so and no nightly versions had been cut.

*Or I suppose you don't trust the supply chain, and you either aren't satisfied with or can't create tooling that checks the hash against a lockfile, but then you have the same problem with literally any other compiler for any language.

[rcxdude]

Indeed. If I'm specifying a hash for anything I'm definitely not leaving things up to the very, very wide range of behaviours covered by the C and C++ standards.