incorrect visitor use

[estebank]

No description provided.

[rust-highfive]

r? @jackh726

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[petrochenkov]

This is not what I was talking about in #90519, all the marks are already added in the TraitDef::span span (self.span in fn create_derived_impl).

This visitor only needs to replace the visited span's context with the TraitDef::span context while keeping the location.

fn visit_span(&mut self, span: &mut Span) {
    *span = span.with_ctxt(self.self_span_from_TraitDef);
}

[estebank]

When doing that I get failures during bootstrap when computing derives, so I assumed I was doing something wrong:

error[E0412]: cannot find type `Range` in this scope
   --> library/core/src/ops/range.rs:78:37
    |
78  |   #[derive(Clone, Default, PartialEq, Eq, Hash)] // not Copy -- see #27186
    |                                       ^^
    |                                       |
    |                                       not found in this scope
    |                                       in this derive macro expansion
    |
   ::: library/core/src/cmp.rs:293:1
    |
293 | / pub macro Eq($item:item) {
294 | |     /* compiler built-in */
295 | | }
    | |_- in this expansion of `#[derive(Eq)]`
    |
help: consider importing this struct
    |
1   | use crate::ops::Range;

With the apply_mark approach on the other hand I could get through bootstrap consistently.

[petrochenkov]

Ah, of course, some parts of the output should not be visited, after all.

The Foo parts, specifically, i.e. references to the type for which we are deriving the impl.

#[derive(Default)]
struct Foo;

#[automatically_derived]
#[allow(unused_qualifications)]
impl ::core::default::Default for Foo {
    #[inline]
    fn default() -> Foo { Foo{} }
}

[petrochenkov]

Let's just land #90519 with all the pre-existing issues left in place, and no MutVisitor.
I'll look how to fix this in a more centralized way.