Regression test for this particular change.

Author: pnkfelix

src/test/ui/nll/issue-52059-report-when-borrow-and-drop-conflict.rs

@@ -0,0 +1,33 @@
+// rust-lang/rust#52059: Regardless of whether you are moving out of a
+// Drop type or just introducing an inadvertant alias via a borrow of
+// one of its fields, it is useful to be reminded of the significance
+// of the fact that the type implements Drop.
+
+#![feature(nll)]
+#![allow(dead_code)]
+
+pub struct S<'a> { url: &'a mut String }
+
+impl<'a> Drop for S<'a> { fn drop(&mut self) { } }
+
+fn finish_1(s: S) -> &mut String {
+    s.url
+}
+//~^^ ERROR borrow may still be in use when destructor runs
+
+fn finish_2(s: S) -> &mut String {
+    let p = &mut *s.url; p
+}
+//~^^ ERROR borrow may still be in use when destructor runs
+
+fn finish_3(s: S) -> &mut String {
+    let p: &mut _ = s.url; p
+}
+//~^^ ERROR borrow may still be in use when destructor runs
+
+fn finish_4(s: S) -> &mut String {
+    let p = s.url; p
+}
+//~^^ ERROR cannot move out of type `S<'_>`, which implements the `Drop` trait
+
+fn main() {}

src/test/ui/nll/issue-52059-report-when-borrow-and-drop-conflict.stderr

@@ -0,0 +1,61 @@
+error[E0713]: borrow may still be in use when destructor runs
+  --> $DIR/issue-52059-report-when-borrow-and-drop-conflict.rs:14:5
+   |
+LL |     s.url
+   |     ^^^^^
+LL | }
+   | - here, drop of `s` needs exclusive access to `*s.url`, because the type `S<'_>` implements the `Drop` trait
+   |
+note: borrowed value must be valid for the anonymous lifetime #1 defined on the function body at 13:1...
+  --> $DIR/issue-52059-report-when-borrow-and-drop-conflict.rs:13:1
+   |
+LL | / fn finish_1(s: S) -> &mut String {
+LL | |     s.url
+LL | | }
+   | |_^
+
+error[E0713]: borrow may still be in use when destructor runs
+  --> $DIR/issue-52059-report-when-borrow-and-drop-conflict.rs:19:13
+   |
+LL |     let p = &mut *s.url; p
+   |             ^^^^^^^^^^^
+LL | }
+   | - here, drop of `s` needs exclusive access to `*s.url`, because the type `S<'_>` implements the `Drop` trait
+   |
+note: borrowed value must be valid for the anonymous lifetime #1 defined on the function body at 18:1...
+  --> $DIR/issue-52059-report-when-borrow-and-drop-conflict.rs:18:1
+   |
+LL | / fn finish_2(s: S) -> &mut String {
+LL | |     let p = &mut *s.url; p
+LL | | }
+   | |_^
+
+error[E0713]: borrow may still be in use when destructor runs
+  --> $DIR/issue-52059-report-when-borrow-and-drop-conflict.rs:24:21
+   |
+LL |     let p: &mut _ = s.url; p
+   |                     ^^^^^
+LL | }
+   | - here, drop of `s` needs exclusive access to `*s.url`, because the type `S<'_>` implements the `Drop` trait
+   |
+note: borrowed value must be valid for the anonymous lifetime #1 defined on the function body at 23:1...
+  --> $DIR/issue-52059-report-when-borrow-and-drop-conflict.rs:23:1
+   |
+LL | / fn finish_3(s: S) -> &mut String {
+LL | |     let p: &mut _ = s.url; p
+LL | | }
+   | |_^
+
+error[E0509]: cannot move out of type `S<'_>`, which implements the `Drop` trait
+  --> $DIR/issue-52059-report-when-borrow-and-drop-conflict.rs:29:13
+   |
+LL |     let p = s.url; p
+   |             ^^^^^
+   |             |
+   |             cannot move out of here
+   |             help: consider borrowing here: `&s.url`
+
+error: aborting due to 4 previous errors
+
+Some errors occurred: E0509, E0713.
+For more information about an error, try `rustc --explain E0509`.