[a1369209993]

> rustc will never rely on whitespace for proper tokenization

Huh? That seems clearly untrue, eg `fnfoo` vs `fn foo` or `x && y` vs `x & &y` or `x<<shift_or_type > ::foo` vs `x < <shift_or_type>::foo`? Presumably for some or all of those, one version ends up being a error (eg bitwise and with a pointer from `x & &y` probably doesn't work), but that's not at the level of tokenization.

[ChrisSD]

Given the context, I think they simply mean that a-b is interpreted the same as a - b.

It can't be interpreted as a single identifier.