add more sensible mut-ref-to-immutable test

Author: RalfJung

tests/ui/consts/const-mut-refs/mut_ref_in_final.rs

@@ -26,6 +26,8 @@ const B4: Option<&mut i32> = helper(&mut 42); //~ ERROR temporary value dropped
 // Not ok, since it points to read-only memory.
 const IMMUT_MUT_REF: &mut u16 = unsafe { mem::transmute(&13) };
 //~^ ERROR pointing to read-only memory
+static IMMUT_MUT_REF_STATIC: &mut u16 = unsafe { mem::transmute(&13) };
+//~^ ERROR pointing to read-only memory
 
 // Ok, because no references to mutable data exist here, since the `{}` moves
 // its value and then takes a reference to that.

tests/ui/consts/const-mut-refs/mut_ref_in_final.stderr

@@ -31,8 +31,19 @@ LL | const IMMUT_MUT_REF: &mut u16 = unsafe { mem::transmute(&13) };
                HEX_DUMP
            }
 
+error[E0080]: constructing invalid value: encountered mutable reference or box pointing to read-only memory
+  --> $DIR/mut_ref_in_final.rs:29:1
+   |
+LL | static IMMUT_MUT_REF_STATIC: &mut u16 = unsafe { mem::transmute(&13) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ it is undefined behavior to use this value
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: $SIZE, align: $ALIGN) {
+               HEX_DUMP
+           }
+
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/mut_ref_in_final.rs:50:65
+  --> $DIR/mut_ref_in_final.rs:52:65
    |
 LL | const FOO: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
    |                                  -------------------------------^^--
@@ -42,7 +53,7 @@ LL | const FOO: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
    |                                  using this value as a constant requires that borrow lasts for `'static`
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/mut_ref_in_final.rs:53:67
+  --> $DIR/mut_ref_in_final.rs:55:67
    |
 LL | static FOO2: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
    |                                    -------------------------------^^--
@@ -52,7 +63,7 @@ LL | static FOO2: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
    |                                    using this value as a static requires that borrow lasts for `'static`
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/mut_ref_in_final.rs:56:71
+  --> $DIR/mut_ref_in_final.rs:58:71
    |
 LL | static mut FOO3: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
    |                                        -------------------------------^^--
@@ -62,30 +73,30 @@ LL | static mut FOO3: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
    |                                        using this value as a static requires that borrow lasts for `'static`
 
 error[E0764]: mutable references are not allowed in the final value of statics
-  --> $DIR/mut_ref_in_final.rs:69:53
+  --> $DIR/mut_ref_in_final.rs:71:53
    |
 LL | static RAW_MUT_CAST_S: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
    |                                                     ^^^^^^^
 
 error[E0764]: mutable references are not allowed in the final value of statics
-  --> $DIR/mut_ref_in_final.rs:71:54
+  --> $DIR/mut_ref_in_final.rs:73:54
    |
 LL | static RAW_MUT_COERCE_S: SyncPtr<i32> = SyncPtr { x: &mut 0 };
    |                                                      ^^^^^^
 
 error[E0764]: mutable references are not allowed in the final value of constants
-  --> $DIR/mut_ref_in_final.rs:73:52
+  --> $DIR/mut_ref_in_final.rs:75:52
    |
 LL | const RAW_MUT_CAST_C: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
    |                                                    ^^^^^^^
 
 error[E0764]: mutable references are not allowed in the final value of constants
-  --> $DIR/mut_ref_in_final.rs:75:53
+  --> $DIR/mut_ref_in_final.rs:77:53
    |
 LL | const RAW_MUT_COERCE_C: SyncPtr<i32> = SyncPtr { x: &mut 0 };
    |                                                     ^^^^^^
 
-error: aborting due to 11 previous errors
+error: aborting due to 12 previous errors
 
 Some errors have detailed explanations: E0080, E0716, E0764.
 For more information about an error, try `rustc --explain E0080`.