diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index 1ea4ca375f1..dfc726efeb9 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -444,6 +444,9 @@ passes_macro_export_on_decl_macro =
passes_macro_use =
`#[{$name}]` only has an effect on `extern crate` and modules
+passes_may_dangle =
+ `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+
passes_maybe_string_interpolation = you might have meant to use string interpolation in this string literal
passes_missing_const_err =
attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
@@ -475,8 +478,8 @@ passes_multiple_start_functions =
.previous = previous `#[start]` function here
passes_must_not_suspend =
- `must_not_suspend` attribute should be applied to a struct, enum, or trait
- .label = is not a struct, enum, or trait
+ `must_not_suspend` attribute should be applied to a struct, enum, union, or trait
+ .label = is not a struct, enum, union, or trait
passes_must_use_async =
`must_use` attribute on `async` functions applies to the anonymous `Future` returned by the function, not the value within
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index a47add929eb..e3c2999142f 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -189,6 +189,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
[sym::collapse_debuginfo, ..] => self.check_collapse_debuginfo(attr, span, target),
[sym::must_not_suspend, ..] => self.check_must_not_suspend(attr, span, target),
[sym::must_use, ..] => self.check_must_use(hir_id, attr, target),
+ [sym::may_dangle, ..] => self.check_may_dangle(hir_id, attr),
[sym::rustc_pass_by_value, ..] => self.check_pass_by_value(attr, span, target),
[sym::rustc_allow_incoherent_impl, ..] => {
self.check_allow_incoherent_impl(attr, span, target)
@@ -255,7 +256,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
| sym::cfg_attr
// need to be fixed
| sym::cfi_encoding // FIXME(cfi_encoding)
- | sym::may_dangle // FIXME(dropck_eyepatch)
| sym::pointee // FIXME(derive_smart_pointer)
| sym::omit_gdb_pretty_printer_section // FIXME(omit_gdb_pretty_printer_section)
| sym::used // handled elsewhere to restrict to static items
@@ -1363,7 +1363,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
}
}
- /// Checks if `#[must_not_suspend]` is applied to a function.
+ /// Checks if `#[must_not_suspend]` is applied to a struct, enum, union, or trait.
fn check_must_not_suspend(&self, attr: &Attribute, span: Span, target: Target) {
match target {
Target::Struct | Target::Enum | Target::Union | Target::Trait => {}
@@ -1373,6 +1373,27 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
}
}
+ /// Checks if `#[may_dangle]` is applied to a lifetime or type generic parameter in `Drop` impl.
+ fn check_may_dangle(&self, hir_id: HirId, attr: &Attribute) {
+ if let hir::Node::GenericParam(param) = self.tcx.hir_node(hir_id)
+ && matches!(
+ param.kind,
+ hir::GenericParamKind::Lifetime { .. } | hir::GenericParamKind::Type { .. }
+ )
+ && matches!(param.source, hir::GenericParamSource::Generics)
+ && let parent_hir_id = self.tcx.parent_hir_id(hir_id)
+ && let hir::Node::Item(item) = self.tcx.hir_node(parent_hir_id)
+ && let hir::ItemKind::Impl(impl_) = item.kind
+ && let Some(trait_) = impl_.of_trait
+ && let Some(def_id) = trait_.trait_def_id()
+ && self.tcx.is_lang_item(def_id, hir::LangItem::Drop)
+ {
+ return;
+ }
+
+ self.dcx().emit_err(errors::InvalidMayDangle { attr_span: attr.span });
+ }
+
/// Checks if `#[cold]` is applied to a non-function.
fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
match target {
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 3a043e0e3c1..ee7d097e5d3 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -737,6 +737,13 @@ pub struct NonExportedMacroInvalidAttrs {
pub attr_span: Span,
}
+#[derive(Diagnostic)]
+#[diag(passes_may_dangle)]
+pub struct InvalidMayDangle {
+ #[primary_span]
+ pub attr_span: Span,
+}
+
#[derive(LintDiagnostic)]
#[diag(passes_unused_duplicate)]
pub struct UnusedDuplicate {
diff --git a/tests/ui/attributes/may_dangle.rs b/tests/ui/attributes/may_dangle.rs
new file mode 100644
index 00000000000..209ba0e88ad
--- /dev/null
+++ b/tests/ui/attributes/may_dangle.rs
@@ -0,0 +1,53 @@
+#![feature(dropck_eyepatch)]
+
+struct Implee1<'a, T, const N: usize>(&'a T);
+struct Implee2<'a, T, const N: usize>(&'a T);
+struct Implee3<'a, T, const N: usize>(&'a T);
+trait NotDrop {}
+
+unsafe impl<#[may_dangle] 'a, T, const N: usize> NotDrop for Implee1<'a, T, N> {}
+//~^ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl
+
+unsafe impl<'a, #[may_dangle] T, const N: usize> NotDrop for Implee2<'a, T, N> {}
+//~^ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl
+
+unsafe impl<'a, T, #[may_dangle] const N: usize> Drop for Implee1<'a, T, N> {
+ //~^ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl
+ fn drop(&mut self) {}
+}
+
+// Ok, lifetime param in a `Drop` impl.
+unsafe impl<#[may_dangle] 'a, T, const N: usize> Drop for Implee2<'a, T, N> {
+ fn drop(&mut self) {}
+}
+
+// Ok, type param in a `Drop` impl.
+unsafe impl<'a, #[may_dangle] T, const N: usize> Drop for Implee3<'a, T, N> {
+ fn drop(&mut self) {}
+}
+
+// Check that this check is not textual.
+mod fake {
+ trait Drop {
+ fn drop(&mut self);
+ }
+ struct Implee<T>(T);
+
+ unsafe impl<#[may_dangle] T> Drop for Implee<T> {
+ //~^ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl
+ fn drop(&mut self) {}
+ }
+}
+
+#[may_dangle] //~ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl
+struct Dangling;
+
+#[may_dangle] //~ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl
+impl NotDrop for () {
+}
+
+#[may_dangle] //~ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl
+fn main() {
+ #[may_dangle] //~ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl
+ let () = ();
+}
diff --git a/tests/ui/attributes/may_dangle.stderr b/tests/ui/attributes/may_dangle.stderr
new file mode 100644
index 00000000000..dc24f847f71
--- /dev/null
+++ b/tests/ui/attributes/may_dangle.stderr
@@ -0,0 +1,50 @@
+error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+ --> $DIR/may_dangle.rs:8:13
+ |
+LL | unsafe impl<#[may_dangle] 'a, T, const N: usize> NotDrop for Implee1<'a, T, N> {}
+ | ^^^^^^^^^^^^^
+
+error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+ --> $DIR/may_dangle.rs:11:17
+ |
+LL | unsafe impl<'a, #[may_dangle] T, const N: usize> NotDrop for Implee2<'a, T, N> {}
+ | ^^^^^^^^^^^^^
+
+error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+ --> $DIR/may_dangle.rs:14:20
+ |
+LL | unsafe impl<'a, T, #[may_dangle] const N: usize> Drop for Implee1<'a, T, N> {
+ | ^^^^^^^^^^^^^
+
+error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+ --> $DIR/may_dangle.rs:42:1
+ |
+LL | #[may_dangle]
+ | ^^^^^^^^^^^^^
+
+error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+ --> $DIR/may_dangle.rs:45:1
+ |
+LL | #[may_dangle]
+ | ^^^^^^^^^^^^^
+
+error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+ --> $DIR/may_dangle.rs:49:1
+ |
+LL | #[may_dangle]
+ | ^^^^^^^^^^^^^
+
+error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+ --> $DIR/may_dangle.rs:51:5
+ |
+LL | #[may_dangle]
+ | ^^^^^^^^^^^^^
+
+error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+ --> $DIR/may_dangle.rs:36:17
+ |
+LL | unsafe impl<#[may_dangle] T> Drop for Implee<T> {
+ | ^^^^^^^^^^^^^
+
+error: aborting due to 8 previous errors
+
diff --git a/tests/ui/lint/must_not_suspend/other_items.stderr b/tests/ui/lint/must_not_suspend/other_items.stderr
index e6c36b78951..dff5210b7e4 100644
--- a/tests/ui/lint/must_not_suspend/other_items.stderr
+++ b/tests/ui/lint/must_not_suspend/other_items.stderr
@@ -1,10 +1,10 @@
-error: `must_not_suspend` attribute should be applied to a struct, enum, or trait
+error: `must_not_suspend` attribute should be applied to a struct, enum, union, or trait
--> $DIR/other_items.rs:5:1
|
LL | #[must_not_suspend]
| ^^^^^^^^^^^^^^^^^^^
LL | mod inner {}
- | ------------ is not a struct, enum, or trait
+ | ------------ is not a struct, enum, union, or trait
error: aborting due to 1 previous error
diff --git a/tests/ui/lint/must_not_suspend/return.stderr b/tests/ui/lint/must_not_suspend/return.stderr
index 5a73064c787..440f8165686 100644
--- a/tests/ui/lint/must_not_suspend/return.stderr
+++ b/tests/ui/lint/must_not_suspend/return.stderr
@@ -1,4 +1,4 @@
-error: `must_not_suspend` attribute should be applied to a struct, enum, or trait
+error: `must_not_suspend` attribute should be applied to a struct, enum, union, or trait
--> $DIR/return.rs:5:1
|
LL | #[must_not_suspend]
@@ -6,7 +6,7 @@ LL | #[must_not_suspend]
LL | / fn foo() -> i32 {
LL | | 0
LL | | }
- | |_- is not a struct, enum, or trait
+ | |_- is not a struct, enum, union, or trait
error: aborting due to 1 previous error