Introduce basic Reborrow tests

tests/ui/reborrow/custom_mut.rs

@@ -0,0 +1,13 @@
+#![feature(reborrow)]
+use std::marker::Reborrow;
+
+struct CustomMut<'a, T>(&'a mut T);
+impl<'a, T> Reborrow for CustomMut<'a, T> {}
+
+fn method(a: CustomMut<'_, ()>) {}
+
+fn main() {
+    let a = CustomMut(&mut ());
+    let _ = method(a);
+    let _ = method(a); //~ERROR use of moved value: `a`
+}

tests/ui/reborrow/custom_mut.stderr

@@ -0,0 +1,29 @@
+error[E0382]: use of moved value: `a`
+  --> $DIR/custom_mut.rs:12:20
+   |
+LL |     let a = CustomMut(&mut ());
+   |         - move occurs because `a` has type `CustomMut<'_, ()>`, which does not implement the `Copy` trait
+LL |     let _ = method(a);
+   |                    - value moved here
+LL |     let _ = method(a);
+   |                    ^ value used here after move
+   |
+note: consider changing this parameter type in function `method` to borrow instead if owning the value isn't necessary
+  --> $DIR/custom_mut.rs:7:14
+   |
+LL | fn method(a: CustomMut<'_, ()>) {}
+   |    ------    ^^^^^^^^^^^^^^^^^ this parameter takes ownership of the value
+   |    |
+   |    in this function
+note: if `CustomMut<'_, ()>` implemented `Clone`, you could clone the value
+  --> $DIR/custom_mut.rs:4:1
+   |
+LL | struct CustomMut<'a, T>(&'a mut T);
+   | ^^^^^^^^^^^^^^^^^^^^^^^ consider implementing `Clone` for this type
+...
+LL |     let _ = method(a);
+   |                    - you could clone this value
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0382`.

tests/ui/reborrow/custom_mut_coerce_shared.rs

@@ -0,0 +1,28 @@
+#![feature(reborrow)]
+use std::marker::{Reborrow, CoerceShared};
+
+struct CustomMut<'a, T>(&'a mut T);
+impl<'a, T> Reborrow for CustomMut<'a, T> {}
+impl<'a, T> CoerceShared for CustomMut<'a, T> {
+    type Target = CustomRef<'a, T>;
+}
+
+struct CustomRef<'a, T>(&'a T);
+
+impl<'a, T> Clone for CustomRef<'a, T> {
+    fn clone(&self) -> Self {
+        Self(self.0)
+    }
+}
+impl<'a, T> Copy for CustomRef<'a, T> {}
+
+fn method(a: CustomRef<'_, ()>) {}  //~NOTE function defined here
+
+fn main() {
+    let a = CustomMut(&mut ());
+    method(a);
+    //~^ ERROR mismatched types
+    //~| NOTE expected `CustomRef<'_, ()>`, found `CustomMut<'_, ()>`
+    //~| NOTE arguments to this function are incorrect
+    //~| NOTE expected struct `CustomRef<'_, ()>`
+}

tests/ui/reborrow/custom_mut_coerce_shared.stderr

@@ -0,0 +1,19 @@
+error[E0308]: mismatched types
+  --> $DIR/custom_mut_coerce_shared.rs:23:12
+   |
+LL |     method(a);
+   |     ------ ^ expected `CustomRef<'_, ()>`, found `CustomMut<'_, ()>`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `CustomRef<'_, ()>`
+              found struct `CustomMut<'_, ()>`
+note: function defined here
+  --> $DIR/custom_mut_coerce_shared.rs:19:4
+   |
+LL | fn method(a: CustomRef<'_, ()>) {}
+   |    ^^^^^^ --------------------
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/reborrow/option_mut.rs

@@ -0,0 +1,7 @@
+fn method(a: Option<& mut ()>) {}
+
+fn main() {
+    let a = Some(&mut ());
+    let _ = method(a);
+    let _ = method(a); //~ERROR use of moved value: `a`
+}

tests/ui/reborrow/option_mut.stderr

@@ -0,0 +1,21 @@
+error[E0382]: use of moved value: `a`
+  --> $DIR/option_mut.rs:6:20
+   |
+LL |     let a = Some(&mut ());
+   |         - move occurs because `a` has type `Option<&mut ()>`, which does not implement the `Copy` trait
+LL |     let _ = method(a);
+   |                    - value moved here
+LL |     let _ = method(a);
+   |                    ^ value used here after move
+   |
+note: consider changing this parameter type in function `method` to borrow instead if owning the value isn't necessary
+  --> $DIR/option_mut.rs:1:14
+   |
+LL | fn method(a: Option<& mut ()>) {}
+   |    ------    ^^^^^^^^^^^^^^^^ this parameter takes ownership of the value
+   |    |
+   |    in this function
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0382`.

tests/ui/reborrow/option_mut_coerce_shared.rs

@@ -0,0 +1,11 @@
+fn method(a: Option<&()>) {}  //~NOTE function defined here
+
+fn main() {
+    let a = Some(&mut ());
+    method(a);
+    //~^ ERROR mismatched types
+    //~| NOTE arguments to this function are incorrect
+    //~| NOTE types differ in mutability
+    //~| NOTE expected enum `Option<&()>`
+    //~| NOTE    found enum `Option<&mut ()>`
+}

tests/ui/reborrow/option_mut_coerce_shared.stderr

@@ -0,0 +1,23 @@
+error[E0308]: mismatched types
+  --> $DIR/option_mut_coerce_shared.rs:5:12
+   |
+LL |     method(a);
+   |     ------ ^ types differ in mutability
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected enum `Option<&()>`
+              found enum `Option<&mut ()>`
+note: function defined here
+  --> $DIR/option_mut_coerce_shared.rs:1:4
+   |
+LL | fn method(a: Option<&()>) {}
+   |    ^^^^^^ --------------
+help: try using `.as_deref()` to convert `Option<&mut ()>` to `Option<&()>`
+   |
+LL |     method(a.as_deref());
+   |             +++++++++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/reborrow/pin_mut.rs

@@ -0,0 +1,10 @@
+use std::pin::Pin;
+
+fn method(a: Pin<& mut ()>) {}
+
+fn main() {
+    let a = &mut ();
+    let a = Pin::new(a);
+    let _ = method(a);
+    let _ = method(a); //~ERROR use of moved value: `a`
+}

tests/ui/reborrow/pin_mut.stderr

@@ -0,0 +1,21 @@
+error[E0382]: use of moved value: `a`
+  --> $DIR/pin_mut.rs:9:20
+   |
+LL |     let a = Pin::new(a);
+   |         - move occurs because `a` has type `Pin<&mut ()>`, which does not implement the `Copy` trait
+LL |     let _ = method(a);
+   |                    - value moved here
+LL |     let _ = method(a);
+   |                    ^ value used here after move
+   |
+note: consider changing this parameter type in function `method` to borrow instead if owning the value isn't necessary
+  --> $DIR/pin_mut.rs:3:14
+   |
+LL | fn method(a: Pin<& mut ()>) {}
+   |    ------    ^^^^^^^^^^^^^ this parameter takes ownership of the value
+   |    |
+   |    in this function
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0382`.

tests/ui/reborrow/pin_mut_coerce_shared.rs

@@ -0,0 +1,14 @@
+use std::pin::Pin;
+
+fn method(a: Pin<&()>) {}  //~NOTE function defined here
+
+fn main() {
+    let a = &mut ();
+    let a = Pin::new(a);
+    method(a);
+    //~^ ERROR mismatched types
+    //~| NOTE arguments to this function are incorrect
+    //~| NOTE types differ in mutability
+    //~| NOTE expected struct `Pin<&()>`
+    //~| NOTE    found struct `Pin<&mut ()>`
+}

tests/ui/reborrow/pin_mut_coerce_shared.stderr

@@ -0,0 +1,19 @@
+error[E0308]: mismatched types
+  --> $DIR/pin_mut_coerce_shared.rs:8:12
+   |
+LL |     method(a);
+   |     ------ ^ types differ in mutability
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `Pin<&()>`
+              found struct `Pin<&mut ()>`
+note: function defined here
+  --> $DIR/pin_mut_coerce_shared.rs:3:4
+   |
+LL | fn method(a: Pin<&()>) {}
+   |    ^^^^^^ -----------
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.