Add test for E0796 error

Add test for `static_mut_ref` lint

tests/ui/borrowck/borrowck-unsafe-static-mutable-borrows.rs

@@ -2,17 +2,22 @@
 
 // Test file taken from issue 45129 (https://github.com/rust-lang/rust/issues/45129)
 
-struct Foo { x: [usize; 2] }
+struct Foo {
+    x: [usize; 2],
+}
 
 static mut SFOO: Foo = Foo { x: [23, 32] };
 
 impl Foo {
-    fn x(&mut self) -> &mut usize { &mut self.x[0] }
+    fn x(&mut self) -> &mut usize {
+        &mut self.x[0]
+    }
 }
 
 fn main() {
     unsafe {
         let sfoo: *mut Foo = &mut SFOO;
+        //~^ WARN use of mutable static is discouraged [static_mut_ref]
         let x = (*sfoo).x();
         (*sfoo).x[1] += 1;
         *x += 1;

tests/ui/borrowck/borrowck-unsafe-static-mutable-borrows.stderr

@@ -0,0 +1,16 @@
+warning: use of mutable static is discouraged
+  --> $DIR/borrowck-unsafe-static-mutable-borrows.rs:19:30
+   |
+LL |         let sfoo: *mut Foo = &mut SFOO;
+   |                              ^^^^^^^^^ use of mutable static
+   |
+   = note: use of mutable static is a hard error from 2024 edition
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+   = note: `#[warn(static_mut_ref)]` on by default
+help: use `addr_of_mut!` macro
+   |
+LL |         let sfoo: *mut Foo = addr_of_mut!(SFOO);
+   |                              ~~~~~~~~~~~~~~~~~~
+
+warning: 1 warning emitted
+

tests/ui/static/use_of_mutable_static_unsafe_block.e2015.stderr

@@ -0,0 +1,20 @@
+error: use of mutable static is discouraged
+  --> $DIR/use_of_mutable_static_unsafe_block.rs:18:18
+   |
+LL |         let _y = &X;
+   |                  ^^ use of mutable static
+   |
+   = note: use of mutable static is a hard error from 2024 edition
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+note: the lint level is defined here
+  --> $DIR/use_of_mutable_static_unsafe_block.rs:8:9
+   |
+LL | #![deny(static_mut_ref)]
+   |         ^^^^^^^^^^^^^^
+help: use `addr_of_mut!` macro
+   |
+LL |         let _y = addr_of_mut!(X);
+   |                  ~~~~~~~~~~~~~~~
+
+error: aborting due to previous error
+

tests/ui/static/use_of_mutable_static_unsafe_block.e2018.stderr

@@ -0,0 +1,20 @@
+error: use of mutable static is discouraged
+  --> $DIR/use_of_mutable_static_unsafe_block.rs:18:18
+   |
+LL |         let _y = &X;
+   |                  ^^ use of mutable static
+   |
+   = note: use of mutable static is a hard error from 2024 edition
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+note: the lint level is defined here
+  --> $DIR/use_of_mutable_static_unsafe_block.rs:8:9
+   |
+LL | #![deny(static_mut_ref)]
+   |         ^^^^^^^^^^^^^^
+help: use `addr_of_mut!` macro
+   |
+LL |         let _y = addr_of_mut!(X);
+   |                  ~~~~~~~~~~~~~~~
+
+error: aborting due to previous error
+

tests/ui/static/use_of_mutable_static_unsafe_block.e2021.stderr

@@ -0,0 +1,20 @@
+error: use of mutable static is discouraged
+  --> $DIR/use_of_mutable_static_unsafe_block.rs:18:18
+   |
+LL |         let _y = &X;
+   |                  ^^ use of mutable static
+   |
+   = note: use of mutable static is a hard error from 2024 edition
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+note: the lint level is defined here
+  --> $DIR/use_of_mutable_static_unsafe_block.rs:8:9
+   |
+LL | #![deny(static_mut_ref)]
+   |         ^^^^^^^^^^^^^^
+help: use `addr_of_mut!` macro
+   |
+LL |         let _y = addr_of_mut!(X);
+   |                  ~~~~~~~~~~~~~~~
+
+error: aborting due to previous error
+

tests/ui/static/use_of_mutable_static_unsafe_block.e2024.stderr

@@ -0,0 +1,15 @@
+error[E0796]: use of mutable static is disallowed
+  --> $DIR/use_of_mutable_static_unsafe_block.rs:18:18
+   |
+LL |         let _y = &X;
+   |                  ^^ use of mutable static
+   |
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+help: use `addr_of_mut!` macro
+   |
+LL |         let _y = addr_of_mut!(X);
+   |                  ~~~~~~~~~~~~~~~
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0796`.

tests/ui/static/use_of_mutable_static_unsafe_block.rs

@@ -0,0 +1,28 @@
+// revisions: e2015 e2018 e2021 e2024
+
+// [e2015] edition:2015
+// [e2018] edition:2018
+// [e2021] edition:2021
+// [e2024] compile-flags: --edition 2024 -Zunstable-options
+
+#![deny(static_mut_ref)]
+
+use std::ptr::addr_of_mut;
+
+fn main() {
+    static mut X: i32 = 1;
+
+    static mut FOO: [u8; 3] = [1, 2, 3];
+
+    unsafe {
+        let _y = &X;
+        //[e2024]~^ ERROR use of mutable static is disallowed
+        //[e2021]~^^ ERROR use of mutable static is discouraged [static_mut_ref]
+        //[e2018]~^^^ ERROR use of mutable static is discouraged [static_mut_ref]
+        //[e2015]~^^^^ ERROR use of mutable static is discouraged [static_mut_ref]
+
+        let _z = addr_of_mut!(X);
+
+        let _ = FOO.len();
+    }
+}

tests/ui/static/use_of_mutable_static_unsafe_fn.e2015.stderr

@@ -0,0 +1,20 @@
+error: use of mutable static is discouraged
+  --> $DIR/use_of_mutable_static_unsafe_fn.rs:14:14
+   |
+LL |     let _y = &X;
+   |              ^^ use of mutable static
+   |
+   = note: use of mutable static is a hard error from 2024 edition
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+note: the lint level is defined here
+  --> $DIR/use_of_mutable_static_unsafe_fn.rs:8:9
+   |
+LL | #![deny(static_mut_ref)]
+   |         ^^^^^^^^^^^^^^
+help: use `addr_of_mut!` macro
+   |
+LL |     let _y = addr_of_mut!(X);
+   |              ~~~~~~~~~~~~~~~
+
+error: aborting due to previous error
+

tests/ui/static/use_of_mutable_static_unsafe_fn.e2018.stderr

@@ -0,0 +1,20 @@
+error: use of mutable static is discouraged
+  --> $DIR/use_of_mutable_static_unsafe_fn.rs:14:14
+   |
+LL |     let _y = &X;
+   |              ^^ use of mutable static
+   |
+   = note: use of mutable static is a hard error from 2024 edition
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+note: the lint level is defined here
+  --> $DIR/use_of_mutable_static_unsafe_fn.rs:8:9
+   |
+LL | #![deny(static_mut_ref)]
+   |         ^^^^^^^^^^^^^^
+help: use `addr_of_mut!` macro
+   |
+LL |     let _y = addr_of_mut!(X);
+   |              ~~~~~~~~~~~~~~~
+
+error: aborting due to previous error
+

tests/ui/static/use_of_mutable_static_unsafe_fn.e2021.stderr

@@ -0,0 +1,20 @@
+error: use of mutable static is discouraged
+  --> $DIR/use_of_mutable_static_unsafe_fn.rs:14:14
+   |
+LL |     let _y = &X;
+   |              ^^ use of mutable static
+   |
+   = note: use of mutable static is a hard error from 2024 edition
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+note: the lint level is defined here
+  --> $DIR/use_of_mutable_static_unsafe_fn.rs:8:9
+   |
+LL | #![deny(static_mut_ref)]
+   |         ^^^^^^^^^^^^^^
+help: use `addr_of_mut!` macro
+   |
+LL |     let _y = addr_of_mut!(X);
+   |              ~~~~~~~~~~~~~~~
+
+error: aborting due to previous error
+

tests/ui/static/use_of_mutable_static_unsafe_fn.e2024.stderr

@@ -0,0 +1,15 @@
+error[E0796]: use of mutable static is disallowed
+  --> $DIR/use_of_mutable_static_unsafe_fn.rs:14:14
+   |
+LL |     let _y = &X;
+   |              ^^ use of mutable static
+   |
+   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior
+help: use `addr_of_mut!` macro
+   |
+LL |     let _y = addr_of_mut!(X);
+   |              ~~~~~~~~~~~~~~~
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0796`.

tests/ui/static/use_of_mutable_static_unsafe_fn.rs

@@ -0,0 +1,19 @@
+// revisions: e2015 e2018 e2021 e2024
+
+// [e2015] edition:2015
+// [e2018] edition:2018
+// [e2021] edition:2021
+// [e2024] compile-flags: --edition 2024 -Zunstable-options
+
+#![deny(static_mut_ref)]
+
+fn main() {}
+
+unsafe fn _foo() {
+    static mut X: i32 = 1;
+    let _y = &X;
+    //[e2024]~^ ERROR use of mutable static is disallowed
+    //[e2021]~^^ ERROR use of mutable static is discouraged [static_mut_ref]
+    //[e2018]~^^^ ERROR use of mutable static is discouraged [static_mut_ref]
+    //[e2015]~^^^^ ERROR use of mutable static is discouraged [static_mut_ref]
+}