Add question about inference & method lookup

[ChayimFriedman2]

This came up on Zulip.

This is a very hard question, and depends on non-specified inner workings of the inference algorithm, so you may not want to add it.

[peterjoel]

This is a great one!

[dtolnay]

depends on non-specified inner workings of the inference algorithm, so you may not want to add it.

This is my impression as well. I think whatever is learned from this question is not as useful to know as what is learned from most others, so adding it would dilute the value overall.

Thanks anyway for the PR!

[peterjoel]

I thought the purpose of this quiz was to highlight quirks in the Rust language as well as the minutiae of how things really work. Stuff like this is especially useful to macro authors, who need to take care of exactly these sorts of edge cases.

I don't think it's more esoteric than #8 or #24, and probably a few others too.

[dtolnay]

I think it is significantly more esoteric than either of those.