Add tests

src/test/ui/borrowck/issue-81365-1.stderr

@@ -1,5 +1,5 @@
 error[E0506]: cannot assign to `self.container_field` because it is borrowed
-  --> $DIR/issue-81365.rs:21:9
+  --> $DIR/issue-81365-1.rs:21:9
    |
 LL |         let first = &self.target_field;
    |                      ---- borrow of `self.container_field` occurs here

src/test/ui/borrowck/issue-81365-10.rs

@@ -0,0 +1,26 @@
+use std::ops::Deref;
+
+struct DerefTarget {
+    target_field: bool,
+}
+struct Container {
+    target: DerefTarget,
+    container_field: bool,
+}
+
+impl Deref for Container {
+    type Target = DerefTarget;
+    fn deref(&self) -> &Self::Target {
+        &self.target
+    }
+}
+
+impl Container {
+    fn bad_borrow(&mut self) {
+        let first = &self.deref().target_field;
+        self.container_field = true; //~ ERROR E0506
+        first;
+    }
+}
+
+fn main() {}

src/test/ui/borrowck/issue-81365-10.stderr

@@ -0,0 +1,13 @@
+error[E0506]: cannot assign to `self.container_field` because it is borrowed
+  --> $DIR/issue-81365-10.rs:21:9
+   |
+LL |         let first = &self.deref().target_field;
+   |                      ---- borrow of `self.container_field` occurs here
+LL |         self.container_field = true;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to borrowed `self.container_field` occurs here
+LL |         first;
+   |         ----- borrow later used here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0506`.

src/test/ui/borrowck/issue-81365-11.rs

@@ -0,0 +1,32 @@
+use std::ops::{Deref, DerefMut};
+
+struct DerefTarget {
+    target_field: bool,
+}
+struct Container {
+    target: DerefTarget,
+    container_field: bool,
+}
+
+impl Deref for Container {
+    type Target = DerefTarget;
+    fn deref(&self) -> &Self::Target {
+        &self.target
+    }
+}
+
+impl DerefMut for Container {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.target
+    }
+}
+
+impl Container {
+    fn bad_borrow(&mut self) {
+        let first = &mut self.target_field;
+        self.container_field = true; //~ ERROR E0506
+        first;
+    }
+}
+
+fn main() {}

src/test/ui/borrowck/issue-81365-11.stderr

@@ -0,0 +1,13 @@
+error[E0506]: cannot assign to `self.container_field` because it is borrowed
+  --> $DIR/issue-81365-11.rs:27:9
+   |
+LL |         let first = &mut self.target_field;
+   |                          ---- borrow of `self.container_field` occurs here
+LL |         self.container_field = true;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to borrowed `self.container_field` occurs here
+LL |         first;
+   |         ----- borrow later used here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0506`.

src/test/ui/borrowck/issue-81365-8.stderr

@@ -0,0 +1,15 @@
+error[E0506]: cannot assign to `self.container_field` because it is borrowed
+  --> $DIR/issue-81365-8.rs:21:9
+   |
+LL |         let first = &(*self).target_field;
+   |                      ------- borrow of `self.container_field` occurs here
+LL |         self.container_field = true;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to borrowed `self.container_field` occurs here
+LL |         first;
+   |         ----- borrow later used here
+   |
+   = note: borrow occurs due to deref coercion to `DerefTarget`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0506`.

src/test/ui/borrowck/issue-81365-9.rs

@@ -0,0 +1,26 @@
+use std::ops::Deref;
+
+struct DerefTarget {
+    target_field: bool,
+}
+struct Container {
+    target: DerefTarget,
+    container_field: bool,
+}
+
+impl Deref for Container {
+    type Target = DerefTarget;
+    fn deref(&self) -> &Self::Target {
+        &self.target
+    }
+}
+
+impl Container {
+    fn bad_borrow(&mut self) {
+        let first = &Deref::deref(self).target_field;
+        self.container_field = true; //~ ERROR E0506
+        first;
+    }
+}
+
+fn main() {}

src/test/ui/borrowck/issue-81365-9.stderr

@@ -0,0 +1,13 @@
+error[E0506]: cannot assign to `self.container_field` because it is borrowed
+  --> $DIR/issue-81365-9.rs:21:9
+   |
+LL |         let first = &Deref::deref(self).target_field;
+   |                                   ---- borrow of `self.container_field` occurs here
+LL |         self.container_field = true;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to borrowed `self.container_field` occurs here
+LL |         first;
+   |         ----- borrow later used here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0506`.