False positive for inherent_to_string_shadow_display?

I think I found a false positive or at least questionable case of inherent_to_string_shadow_display rule triggering.

The place this rule is (or rather "was", since I disabled it) triggered:
https://github.com/huxi/rusty_ulid/blob/72ac82736311981d12c339b78756049f48406179/src/lib.rs#L557

The place where the method in question is used to actually implement Display:
https://github.com/huxi/rusty_ulid/blob/72ac82736311981d12c339b78756049f48406179/src/lib.rs#L571

This boils down to a situation where a type has an efficient implementation of fn to_string(&self) -> String that is used to implement fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> of fmt::Display.

I think this case (method is used to implement trait) shouldn't trigger the rule.

Start by examining the linked rusty_ulid implementation at src/lib.rs lines 557 and 571, then locate the Clippy implementation and tests for inherent_to_string_shadow_display. Reproduce the lint with a type whose efficient to_string method is used by its Display implementation. Done means this valid trait-implementation pattern no longer triggers the lint while ordinary shadowing cases remain covered.