diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index 68e62c9789aed..c822237413c70 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -508,3 +508,6 @@ lint_opaque_hidden_inferred_bound = opaque type `{$ty}` does not satisfy its ass
.specifically = this associated type bound is unsatisfied for `{$proj_ty}`
lint_opaque_hidden_inferred_bound_sugg = add this bound
+
+lint_useless_anonymous_reexport = useless anonymous re-export
+ .note = only anonymous re-exports of traits are useful, this is {$article} `{$desc}`
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index b3578540516d0..c2cc2fcdf551a 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -74,6 +74,7 @@ mod opaque_hidden_inferred_bound;
mod pass_by_value;
mod passes;
mod redundant_semicolon;
+mod reexports;
mod traits;
mod types;
mod unused;
@@ -111,6 +112,7 @@ use noop_method_call::*;
use opaque_hidden_inferred_bound::*;
use pass_by_value::*;
use redundant_semicolon::*;
+use reexports::*;
use traits::*;
use types::*;
use unused::*;
@@ -242,6 +244,7 @@ late_lint_methods!(
OpaqueHiddenInferredBound: OpaqueHiddenInferredBound,
MultipleSupertraitUpcastable: MultipleSupertraitUpcastable,
MapUnitFn: MapUnitFn,
+ UselessAnonymousReexport: UselessAnonymousReexport,
]
]
);
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 20ab0af585651..8d058517118c4 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1530,3 +1530,11 @@ pub struct UnusedAllocationDiag;
#[derive(LintDiagnostic)]
#[diag(lint_unused_allocation_mut)]
pub struct UnusedAllocationMutDiag;
+
+#[derive(LintDiagnostic)]
+#[diag(lint_useless_anonymous_reexport)]
+#[note]
+pub struct UselessAnonymousReexportDiag {
+ pub article: &'static str,
+ pub desc: &'static str,
+}
diff --git a/compiler/rustc_lint/src/reexports.rs b/compiler/rustc_lint/src/reexports.rs
new file mode 100644
index 0000000000000..8737a57ea0264
--- /dev/null
+++ b/compiler/rustc_lint/src/reexports.rs
@@ -0,0 +1,82 @@
+use crate::lints::UselessAnonymousReexportDiag;
+use crate::{LateContext, LateLintPass, LintContext};
+use rustc_hir::def::DefKind;
+use rustc_hir::def_id::DefId;
+use rustc_hir::{Item, ItemKind, UseKind};
+use rustc_middle::ty::Visibility;
+use rustc_span::symbol::kw;
+use rustc_span::Span;
+
+declare_lint! {
+ /// The `useless_anonymous_reexport` lint checks if anonymous re-exports
+ /// are re-exports of traits.
+ ///
+ /// ### Example
+ ///
+ /// ```rust,compile_fail
+ /// #![deny(useless_anonymous_reexport)]
+ ///
+ /// mod sub {
+ /// pub struct Bar;
+ /// }
+ ///
+ /// pub use self::sub::Bar as _;
+ /// # fn main() {}
+ /// ```
+ ///
+ /// {{produces}}
+ ///
+ /// ### Explanation
+ ///
+ /// Anonymous re-exports are only useful if it's a re-export of a trait
+ /// in case you want to give access to it. If you re-export any other kind,
+ /// you won't be able to use it since its name won't be accessible.
+ pub USELESS_ANONYMOUS_REEXPORT,
+ Warn,
+ "useless anonymous re-export"
+}
+
+declare_lint_pass!(UselessAnonymousReexport => [USELESS_ANONYMOUS_REEXPORT]);
+
+fn emit_err(cx: &LateContext<'_>, span: Span, def_id: DefId) {
+ let article = cx.tcx.def_descr_article(def_id);
+ let desc = cx.tcx.def_descr(def_id);
+ cx.emit_spanned_lint(
+ USELESS_ANONYMOUS_REEXPORT,
+ span,
+ UselessAnonymousReexportDiag { article, desc },
+ );
+}
+
+impl<'tcx> LateLintPass<'tcx> for UselessAnonymousReexport {
+ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
+ if let ItemKind::Use(path, kind) = item.kind &&
+ !matches!(kind, UseKind::Glob) &&
+ item.ident.name == kw::Underscore &&
+ // We only want re-exports. If it's just a `use X;`, then we ignore it.
+ match cx.tcx.local_visibility(item.owner_id.def_id) {
+ Visibility::Public => true,
+ Visibility::Restricted(level) => {
+ level != cx.tcx.parent_module_from_def_id(item.owner_id.def_id)
+ }
+ }
+ {
+ for def_id in path.res.iter().filter_map(|r| r.opt_def_id()) {
+ match cx.tcx.def_kind(def_id) {
+ DefKind::Trait | DefKind::TraitAlias => {}
+ DefKind::TyAlias => {
+ let ty = cx.tcx.type_of(def_id);
+ if !ty.0.is_trait() {
+ emit_err(cx, item.span, def_id);
+ break;
+ }
+ }
+ _ => {
+ emit_err(cx, item.span, def_id);
+ break;
+ }
+ }
+ }
+ }
+ }
+}
diff --git a/tests/ui/imports/issue-99695-b.fixed b/tests/ui/imports/issue-99695-b.fixed
index 0e60c73b67a44..0f688fa282356 100644
--- a/tests/ui/imports/issue-99695-b.fixed
+++ b/tests/ui/imports/issue-99695-b.fixed
@@ -1,5 +1,5 @@
// run-rustfix
-#![allow(unused, nonstandard_style)]
+#![allow(unused, nonstandard_style, useless_anonymous_reexport)]
mod m {
mod p {
diff --git a/tests/ui/imports/issue-99695-b.rs b/tests/ui/imports/issue-99695-b.rs
index 031443a1f5df8..b433997e53f6a 100644
--- a/tests/ui/imports/issue-99695-b.rs
+++ b/tests/ui/imports/issue-99695-b.rs
@@ -1,5 +1,5 @@
// run-rustfix
-#![allow(unused, nonstandard_style)]
+#![allow(unused, nonstandard_style, useless_anonymous_reexport)]
mod m {
mod p {
diff --git a/tests/ui/imports/issue-99695.fixed b/tests/ui/imports/issue-99695.fixed
index 6bf228b23aad2..17ff409324e34 100644
--- a/tests/ui/imports/issue-99695.fixed
+++ b/tests/ui/imports/issue-99695.fixed
@@ -1,5 +1,5 @@
// run-rustfix
-#![allow(unused, nonstandard_style)]
+#![allow(unused, nonstandard_style, useless_anonymous_reexport)]
mod m {
#[macro_export]
macro_rules! nu {
diff --git a/tests/ui/imports/issue-99695.rs b/tests/ui/imports/issue-99695.rs
index f7199f1497ab0..b8979bcb7345c 100644
--- a/tests/ui/imports/issue-99695.rs
+++ b/tests/ui/imports/issue-99695.rs
@@ -1,5 +1,5 @@
// run-rustfix
-#![allow(unused, nonstandard_style)]
+#![allow(unused, nonstandard_style, useless_anonymous_reexport)]
mod m {
#[macro_export]
macro_rules! nu {
diff --git a/tests/ui/lint/anonymous-reexport.rs b/tests/ui/lint/anonymous-reexport.rs
new file mode 100644
index 0000000000000..5d56ae6f969b5
--- /dev/null
+++ b/tests/ui/lint/anonymous-reexport.rs
@@ -0,0 +1,21 @@
+#![deny(useless_anonymous_reexport)]
+#![crate_type = "rlib"]
+
+mod my_mod {
+ pub trait Foo {}
+ pub type TyFoo = dyn Foo;
+ pub struct Bar;
+ pub type TyBar = Bar;
+}
+
+pub use self::my_mod::Foo as _;
+pub use self::my_mod::TyFoo as _;
+pub use self::my_mod::Bar as _; //~ ERROR
+pub use self::my_mod::TyBar as _; //~ ERROR
+pub use self::my_mod::{Bar as _}; //~ ERROR
+pub use self::my_mod::{Bar as _, Foo as _}; //~ ERROR
+pub use self::my_mod::{Bar as _, TyBar as _};
+//~^ ERROR
+//~| ERROR
+#[allow(unused_imports)]
+use self::my_mod::TyBar as _;
diff --git a/tests/ui/lint/anonymous-reexport.stderr b/tests/ui/lint/anonymous-reexport.stderr
new file mode 100644
index 0000000000000..f4f8b41c417a4
--- /dev/null
+++ b/tests/ui/lint/anonymous-reexport.stderr
@@ -0,0 +1,55 @@
+error: useless anonymous re-export
+ --> $DIR/anonymous-reexport.rs:13:1
+ |
+LL | pub use self::my_mod::Bar as _;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: only anonymous re-exports of traits are useful, this is a `struct`
+note: the lint level is defined here
+ --> $DIR/anonymous-reexport.rs:1:9
+ |
+LL | #![deny(useless_anonymous_reexport)]
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: useless anonymous re-export
+ --> $DIR/anonymous-reexport.rs:14:1
+ |
+LL | pub use self::my_mod::TyBar as _;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: only anonymous re-exports of traits are useful, this is a `type alias`
+
+error: useless anonymous re-export
+ --> $DIR/anonymous-reexport.rs:15:24
+ |
+LL | pub use self::my_mod::{Bar as _};
+ | ^^^^^^^^
+ |
+ = note: only anonymous re-exports of traits are useful, this is a `struct`
+
+error: useless anonymous re-export
+ --> $DIR/anonymous-reexport.rs:16:24
+ |
+LL | pub use self::my_mod::{Bar as _, Foo as _};
+ | ^^^^^^^^
+ |
+ = note: only anonymous re-exports of traits are useful, this is a `struct`
+
+error: useless anonymous re-export
+ --> $DIR/anonymous-reexport.rs:17:24
+ |
+LL | pub use self::my_mod::{Bar as _, TyBar as _};
+ | ^^^^^^^^
+ |
+ = note: only anonymous re-exports of traits are useful, this is a `struct`
+
+error: useless anonymous re-export
+ --> $DIR/anonymous-reexport.rs:17:34
+ |
+LL | pub use self::my_mod::{Bar as _, TyBar as _};
+ | ^^^^^^^^^^
+ |
+ = note: only anonymous re-exports of traits are useful, this is a `type alias`
+
+error: aborting due to 6 previous errors
+