Suggest publicly accessible paths for items in private mod:
When encountering a path in non-import situations that are not reachable
due to privacy constraints, search for any public re-exports that the
user could use instead.
Track whether an import suggestion is offering a re-export.
When encountering a path with private segments, mention if the item at
the final path segment is not publicly accessible at all.
Add item visibility metadata to privacy errors from imports:
On unreachable imports, record the item that was being imported in order
to suggest publicly available re-exports or to be explicit that the item
is not available publicly from any path.
In order to allow this, we add a mode to `resolve_path` that will not
add new privacy errors, nor return early if it encounters one. This way
we can get the `Res` corresponding to the final item in the import,
which is used in the privacy error machinery.
When implementing a public trait with a private super-trait, we now emit
a note that the missing bound is not going to be able to be satisfied,
and we explain the concept of a sealed trait.
This commit reverts a change made in #111425.
It was believed that this change was necessary for implementing type privacy lints, but #111801 showed that it was not necessary.
Quite opposite, the revert fixes some issues.
This fixes#111220 by checking the privacy of tuple constructors using `Self`, so the following code now errors
```rust
mod my {
pub struct Foo(&'static str);
}
impl AsRef<str> for my::Foo {
fn as_ref(&self) -> &str {
let Self(s) = self; // previously compiled, now errors correctly
s
}
}
```
Update `error [E0449]: unnecessary visibility qualifier` to be more clear
This updates the error message `error[E0449]: unnecessary visibility qualifier` by clearly indicating that visibility qualifiers already inherit their visibility from a parent item. The error message previously implied that the qualifiers were permitted, which is not the case anymore.
Resolves#109822.
Something similar was previously removed as a part of #104602, but after this PR all table changes should also be "locally correct" after every update.
