Forbid Reborrow impls for types with destructors

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -115,7 +115,11 @@ fn visit_implementation_of_copy(checker: &Checker<'_>) -> Result<(), ErrorGuaran
         Err(CopyImplementationError::HasDestructor(did)) => {
             let span = tcx.hir_expect_item(impl_did).expect_impl().self_ty.span;
             let impl_ = tcx.def_span(did);
-            Err(tcx.dcx().emit_err(diagnostics::CopyImplOnTypeWithDtor { span, impl_ }))
+            Err(tcx.dcx().emit_err(diagnostics::TraitImplOnTypeWithDtor {
+                span,
+                impl_,
+                trait_name: sym::Copy,
+            }))
         }
         Err(CopyImplementationError::HasUnsafeFields) => {
             let span = tcx.hir_expect_item(impl_did).expect_impl().self_ty.span;
@@ -537,6 +541,15 @@ pub(crate) fn reborrow_info<'tcx>(
         assert_field_type_is_copy(tcx, &infcx, impl_did, param_env, field.ty, field.span)?;
     }
 
+    if let Some(did) = def.destructor(tcx).map(|dtor| dtor.did) {
+        let impl_ = tcx.def_span(did);
+        return Err(tcx.dcx().emit_err(diagnostics::TraitImplOnTypeWithDtor {
+            span,
+            impl_,
+            trait_name: sym::Reborrow,
+        }));
+    }
+
     Ok(())
 }
 

compiler/rustc_hir_analysis/src/diagnostics.rs

@@ -292,13 +292,14 @@ pub(crate) struct FieldAlreadyDeclaredNestedHelp {
 }
 
 #[derive(Diagnostic)]
-#[diag("the trait `Copy` cannot be implemented for this type; the type has a destructor", code = E0184)]
-pub(crate) struct CopyImplOnTypeWithDtor {
+#[diag("the trait `{$trait_name}` cannot be implemented for this type; the type has a destructor", code = E0184)]
+pub(crate) struct TraitImplOnTypeWithDtor {
     #[primary_span]
-    #[label("`Copy` not allowed on types with destructors")]
+    #[label("`{$trait_name}` not allowed on types with destructors")]
     pub span: Span,
     #[note("destructor declared here")]
     pub impl_: Span,
+    pub trait_name: Symbol,
 }
 
 #[derive(Diagnostic)]

tests/ui/reborrow/reborrow-drop.rs

@@ -0,0 +1,14 @@
+//@ compile-flags: --crate-type=lib
+
+#![feature(reborrow)]
+
+use std::marker::Reborrow;
+
+struct MyMut<'a>(&'a mut ());
+
+impl Reborrow for MyMut<'_> {}
+//~^ ERROR the trait `Reborrow` cannot be implemented for this type; the type has a destructor [E0184]
+
+impl Drop for MyMut<'_> {
+    fn drop(&mut self) {}
+}

tests/ui/reborrow/reborrow-drop.stderr

@@ -0,0 +1,15 @@
+error[E0184]: the trait `Reborrow` cannot be implemented for this type; the type has a destructor
+  --> $DIR/reborrow-drop.rs:9:1
+   |
+LL | impl Reborrow for MyMut<'_> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Reborrow` not allowed on types with destructors
+   |
+note: destructor declared here
+  --> $DIR/reborrow-drop.rs:13:5
+   |
+LL |     fn drop(&mut self) {}
+   |     ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0184`.