Temporarily switch invalid_reference_casting lint to allow-by-default

compiler/rustc_lint/src/reference_casting.rs

@@ -12,6 +12,7 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust,compile_fail
+    /// # #![deny(invalid_reference_casting)]
     /// fn x(r: &i32) {
     ///     unsafe {
     ///         *(r as *const i32 as *mut i32) += 1;
@@ -29,7 +30,7 @@ declare_lint! {
     /// `UnsafeCell` is the only way to obtain aliasable data that is considered
     /// mutable.
     INVALID_REFERENCE_CASTING,
-    Deny,
+    Allow,
     "casts of `&T` to `&mut T` without interior mutability"
 }
 

tests/ui/const-generics/issues/issue-100313.rs

@@ -9,7 +9,6 @@ impl <const B: &'static bool> T<B> {
         unsafe {
             *(B as *const bool as *mut bool) = false;
             //~^ ERROR evaluation of constant value failed [E0080]
-            //~| ERROR casting `&T` to `&mut T` is undefined behavior
         }
     }
 }

tests/ui/const-generics/issues/issue-100313.stderr

@@ -1,11 +1,3 @@
-error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/issue-100313.rs:10:13
-   |
-LL |             *(B as *const bool as *mut bool) = false;
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `#[deny(invalid_reference_casting)]` on by default
-
 error[E0080]: evaluation of constant value failed
   --> $DIR/issue-100313.rs:10:13
    |
@@ -18,11 +10,11 @@ note: inside `T::<&true>::set_false`
 LL |             *(B as *const bool as *mut bool) = false;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 note: inside `_`
-  --> $DIR/issue-100313.rs:19:5
+  --> $DIR/issue-100313.rs:18:5
    |
 LL |     x.set_false();
    |     ^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/lint/reference_casting.rs

@@ -1,6 +1,7 @@
 // check-fail
 
 #![feature(ptr_from_ref)]
+#![deny(invalid_reference_casting)]
 
 extern "C" {
     // N.B., mutability can be easily incorrect in FFI calls -- as

tests/ui/lint/reference_casting.stderr

@@ -1,61 +1,65 @@
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:19:9
+  --> $DIR/reference_casting.rs:20:9
    |
 LL |         (*(a as *const _ as *mut String)).push_str(" world");
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: `#[deny(invalid_reference_casting)]` on by default
+note: the lint level is defined here
+  --> $DIR/reference_casting.rs:4:9
+   |
+LL | #![deny(invalid_reference_casting)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:21:9
+  --> $DIR/reference_casting.rs:22:9
    |
 LL |         *(a as *const _ as *mut _) = String::from("Replaced");
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:23:9
+  --> $DIR/reference_casting.rs:24:9
    |
 LL |         *(a as *const _ as *mut String) += " world";
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:25:25
+  --> $DIR/reference_casting.rs:26:25
    |
 LL |         let _num = &mut *(num as *const i32 as *mut i32);
    |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:27:25
+  --> $DIR/reference_casting.rs:28:25
    |
 LL |         let _num = &mut *(num as *const i32).cast_mut();
    |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:29:20
+  --> $DIR/reference_casting.rs:30:20
    |
 LL |         let _num = *{ num as *const i32 }.cast_mut();
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:31:9
+  --> $DIR/reference_casting.rs:32:9
    |
 LL |         *std::ptr::from_ref(num).cast_mut() += 1;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:33:9
+  --> $DIR/reference_casting.rs:34:9
    |
 LL |         *std::ptr::from_ref({ num }).cast_mut() += 1;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:35:9
+  --> $DIR/reference_casting.rs:36:9
    |
 LL |         *{ std::ptr::from_ref(num) }.cast_mut() += 1;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:37:9
+  --> $DIR/reference_casting.rs:38:9
    |
 LL |         *(std::ptr::from_ref({ num }) as *mut i32) += 1;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^