Point at shadowed name binding in `you might have meant to refer to` suggestion

[cjgillot]

    Makes sense, I just would rather we pointed at the ident for the item and not the whole thing.

Originally posted by @estebank in #103111 (comment)

The suggestion was introduced by #103111. The suggestion point to the definition of the suggested item. Pointing to the shadowed identifier would be more precise:

• the ident of the item in case of direct reference;
• the import in case of indirect reference.

[fee1-dead]

For this to work, either we would try to look at the DefKind of the Res as according to the docs, and then make the span point to the item name using the SourceMap if we know how the item looks. Alternatively, we could use guess_head_span to make it a bit more precise. Am I missing something here? Would there be a better way to get the span of the ident of the item?

[cjgillot]

There is probably a simpler way, by storing the Span of the Ident that introduced the name in TypoSuggestion, and use that span instead of trying to get one from the Res.

[zbyrn]

I would like to work on this! Let me know if this is work in progress for someone else!
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