Detect unconstructable re-exported tuple structs

When a tuple-struct is re-exported that has inaccessible fields at the `use` scope, the type's constructor cannot be accessed through that re-export. We now account for this case and extend the resulting resolution error. We also check if the constructor would be accessible directly, not through the re-export, and if so, we suggest using the full path instead.

```
error[E0423]: cannot initialize a tuple struct which contains private fields
  --> $DIR/ctor-not-accessible-due-to-inaccessible-field-in-reexport.rs:12:33
   |
LL |             let crate::Foo(x) = crate::Foo(42);
   |                                 ^^^^^^^^^^
   |
note: the type is accessed through this re-export, but the type's constructor is not visible in this import's scope due to private fields
  --> $DIR/ctor-not-accessible-due-to-inaccessible-field-in-reexport.rs:3:9
   |
LL | pub use my_mod::Foo;
   |         ^^^^^^^^^^^
help: the type can be constructed directly, because its fields are available from the current scope
   |
LL |             let crate::Foo(x) = crate::my_mod::Foo(42);
   |                                 ~~~~~~~~~~~~~~~~~~
```

Fix #133343.

1 files changed, 6 insertions, 0 deletions

diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 8959068b2a6..b44b1c966a4 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -1167,6 +1167,11 @@ pub struct Resolver<'ra, 'tcx> {
     /// Crate-local macro expanded `macro_export` referred to by a module-relative path.
     macro_expanded_macro_export_errors: BTreeSet<(Span, Span)> = BTreeSet::new(),
 
+    /// When a type is re-exported that has an inaccessible constructor because it has fields that
+    /// are inaccessible from the import's scope, we mark that as the type won't be able to be built
+    /// through the re-export. We use this information to extend the existing diagnostic.
+    inaccessible_ctor_reexport: FxHashMap<Span, Span>,
+
     arenas: &'ra ResolverArenas<'ra>,
     dummy_binding: NameBinding<'ra>,
     builtin_types_bindings: FxHashMap<Symbol, NameBinding<'ra>>,
@@ -1595,6 +1600,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             glob_map: Default::default(),
             used_imports: FxHashSet::default(),
             maybe_unused_trait_imports: Default::default(),
+            inaccessible_ctor_reexport: Default::default(),
 
             arenas,
             dummy_binding: arenas.new_pub_res_binding(Res::Err, DUMMY_SP, LocalExpnId::ROOT),