Add warn-by-default lint for local binding shadowing exported glob re-export item

compiler/rustc_lint_defs/src/builtin.rs

@@ -3272,6 +3272,43 @@ declare_lint! {
     "ambiguous glob re-exports",
 }
 
+declare_lint! {
+    /// The `hidden_glob_reexports` lint detects cases where glob re-export items are shadowed by
+    /// private items.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(hidden_glob_reexports)]
+    ///
+    /// pub mod upstream {
+    ///     mod inner { pub struct Foo {}; pub struct Bar {}; }
+    ///     pub use self::inner::*;
+    ///     struct Foo {} // private item shadows `inner::Foo`
+    /// }
+    ///
+    /// // mod downstream {
+    /// //     fn test() {
+    /// //         let _ = crate::upstream::Foo; // inaccessible
+    /// //     }
+    /// // }
+    ///
+    /// pub fn main() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This was previously accepted without any errors or warnings but it could silently break a
+    /// crate's downstream user code. If the `struct Foo` was added, `dep::inner::Foo` would
+    /// silently become inaccessible and trigger a "`struct `Foo` is private`" visibility error at
+    /// the downstream use site.
+    pub HIDDEN_GLOB_REEXPORTS,
+    Warn,
+    "name introduced by a private item shadows a name introduced by a public glob re-export",
+}
+
 declare_lint_pass! {
     /// Does nothing as a lint pass, but registers some `Lint`s
     /// that are used by other parts of the compiler.
@@ -3304,6 +3341,7 @@ declare_lint_pass! {
         FORBIDDEN_LINT_GROUPS,
         FUNCTION_ITEM_REFERENCES,
         FUZZY_PROVENANCE_CASTS,
+        HIDDEN_GLOB_REEXPORTS,
         ILL_FORMED_ATTRIBUTE_INPUT,
         ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
         IMPLIED_BOUNDS_ENTAILMENT,