As discussed below, we cannot make breaking changes to the standard library via the edition system.

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.

I think it's important to draw a distinction between what is true today, and what could be in the future. Today, the RFC text says:

> More generally, breaking changes to the standard library are not possible.

Could we amend this RFC to introduce a system like this? Sure. Have we? No.