The function itself cannot be removed from the standard library (and likewise the symbol can never be reclaimed for a different use), but there's no reason that future editions couldn't report a compiler error when attempting to use the function. The function would only be inaccessible at the source level, not at the linking level, thereby completely preserving cross-edition compatibility while also mandating that crates remove references to it when migrating to a newer edition. Think of it like an edition-specific deprecation lint being turned from warn to deny.