When encoutering a privacy error on an item through a re-export that is
accessible in an alternative path, provide a structured suggestion with
that path.
```
error[E0603]: module import `mem` is private
--> $DIR/private-std-reexport-suggest-public.rs:4:14
|
LL | use foo::mem;
| ^^^ private module import
|
note: the module import `mem` is defined here...
--> $DIR/private-std-reexport-suggest-public.rs:8:9
|
LL | use std::mem;
| ^^^^^^^^
note: ...and refers to the module `mem` which is defined here
--> $SRC_DIR/std/src/lib.rs:LL:COL
|
= note: you could import this
help: import `mem` through the re-export
|
LL | use std::mem;
| ~~~~~~~~
```
Fix#42909.
