From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 src/test/ui/drop/dropck-eyepatch.rs | 102 ++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 src/test/ui/drop/dropck-eyepatch.rs

(limited to 'src/test/ui/drop/dropck-eyepatch.rs')

diff --git a/src/test/ui/drop/dropck-eyepatch.rs b/src/test/ui/drop/dropck-eyepatch.rs
new file mode 100644
index 000000000..3c4840d5c
--- /dev/null
+++ b/src/test/ui/drop/dropck-eyepatch.rs
@@ -0,0 +1,102 @@
+// run-pass
+#![feature(dropck_eyepatch)]
+
+// The point of this test is to illustrate that the `#[may_dangle]`
+// attribute specifically allows, in the context of a type
+// implementing `Drop`, a generic parameter to be instantiated with a
+// lifetime that does not strictly outlive the owning type itself.
+//
+// Here we test that a model use of `#[may_dangle]` will compile and run.
+//
+// The illustration is made concrete by comparison with two variations
+// on the type with `#[may_dangle]`:
+//
+//   1. an analogous type that does not implement `Drop` (and thus
+//      should exhibit maximal flexibility with respect to dropck), and
+//
+//   2. an analogous type that does not use `#[may_dangle]` (and thus
+//      should exhibit the standard limitations imposed by dropck.
+//
+// The types in this file follow a pattern, {D,P,S}{t,r}, where:
+//
+// - D means "I implement Drop"
+//
+// - P means "I implement Drop but guarantee my (first) parameter is
+//     pure, i.e., not accessed from the destructor"; no other parameters
+//     are pure.
+//
+// - S means "I do not implement Drop"
+//
+// - t suffix is used when the first generic is a type
+//
+// - r suffix is used when the first generic is a lifetime.
+
+trait Foo { fn foo(&self, _: &str); }
+
+struct Dt<A: Foo>(&'static str, A);
+struct Dr<'a, B:'a+Foo>(&'static str, &'a B);
+struct Pt<A,B: Foo>(&'static str, #[allow(unused_tuple_struct_fields)] A, B);
+struct Pr<'a, 'b, B:'a+'b+Foo>(&'static str, #[allow(unused_tuple_struct_fields)] &'a B, &'b B);
+struct St<A: Foo>(&'static str, #[allow(unused_tuple_struct_fields)] A);
+struct Sr<'a, B:'a+Foo>(&'static str, #[allow(unused_tuple_struct_fields)] &'a B);
+
+impl<A: Foo> Drop for Dt<A> {
+    fn drop(&mut self) { println!("drop {}", self.0); self.1.foo(self.0); }
+}
+impl<'a, B: Foo> Drop for Dr<'a, B> {
+    fn drop(&mut self) { println!("drop {}", self.0); self.1.foo(self.0); }
+}
+unsafe impl<#[may_dangle] A, B: Foo> Drop for Pt<A, B> {
+    // (unsafe to access self.1  due to #[may_dangle] on A)
+    fn drop(&mut self) { println!("drop {}", self.0); self.2.foo(self.0); }
+}
+unsafe impl<#[may_dangle] 'a, 'b, B: Foo> Drop for Pr<'a, 'b, B> {
+    // (unsafe to access self.1 due to #[may_dangle] on 'a)
+    fn drop(&mut self) { println!("drop {}", self.0); self.2.foo(self.0); }
+}
+
+fn main() {
+    use std::cell::RefCell;
+
+    impl Foo for RefCell<String> {
+        fn foo(&self, s: &str) {
+            let s2 = format!("{}|{}", *self.borrow(), s);
+            *self.borrow_mut() = s2;
+        }
+    }
+
+    impl<'a, T:Foo> Foo for &'a T {
+        fn foo(&self, s: &str) {
+            (*self).foo(s);
+        }
+    }
+
+    struct CheckOnDrop(RefCell<String>, &'static str);
+    impl Drop for CheckOnDrop {
+        fn drop(&mut self) { assert_eq!(*self.0.borrow(), self.1); }
+    }
+
+    let c_long;
+    let (c, dt, dr, pt, pr, st, sr)
+        : (CheckOnDrop, Dt<_>, Dr<_>, Pt<_, _>, Pr<_>, St<_>, Sr<_>);
+    c_long = CheckOnDrop(RefCell::new("c_long".to_string()),
+                         "c_long|pr|pt|dr|dt");
+    c = CheckOnDrop(RefCell::new("c".to_string()),
+                    "c");
+
+    // No error: sufficiently long-lived state can be referenced in dtors
+    dt = Dt("dt", &c_long.0);
+    dr = Dr("dr", &c_long.0);
+
+    // No error: Drop impl asserts .1 (A and &'a _) are not accessed
+    pt = Pt("pt", &c.0, &c_long.0);
+    pr = Pr("pr", &c.0, &c_long.0);
+
+    // No error: St and Sr have no destructor.
+    st = St("st", &c.0);
+    sr = Sr("sr", &c.0);
+
+    println!("{:?}", (dt.0, dr.0, pt.0, pr.0, st.0, sr.0));
+    assert_eq!(*c_long.0.borrow(), "c_long");
+    assert_eq!(*c.0.borrow(), "c");
+}
-- 
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