Error code E0785
An inherent impl
was written on a dyn auto trait.
Erroneous code example:
ⓘ
Dyn objects allow any number of auto traits, plus at most one non-auto trait. The non-auto trait becomes the "principal trait".
When checking if an impl on a dyn trait is coherent, the principal trait is normally the only one considered. Since the erroneous code has no principal trait, it cannot be implemented at all.
Working example: