Update compare-mode=nll stderr files to reflect the fix to #55492.

src/test/ui/borrowck/borrowck-closures-unique.nll.stderr

@@ -40,19 +40,15 @@ LL |     let c2 = || set(x); //~ ERROR two closures require unique access to `x`
 LL |     c1;
    |     -- first borrow later used here
 
-warning[E0594]: cannot assign to `x`, as it is not declared as mutable
+error[E0594]: cannot assign to `x`, as it is not declared as mutable
   --> $DIR/borrowck-closures-unique.rs:57:38
    |
 LL | fn e(x: &'static mut isize) {
    |      - help: consider changing this to be mutable: `mut x`
 LL |     let c1 = |y: &'static mut isize| x = y; //~ ERROR closure cannot assign to immutable argument
    |                                      ^^^^^ cannot assign
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 Some errors occurred: E0500, E0524, E0594.
 For more information about an error, try `rustc --explain E0500`.

src/test/ui/borrowck/borrowck-describe-lvalue.ast.nll.stderr

@@ -20,7 +20,7 @@ LL |                    //[mir]~^ ERROR cannot borrow `x` as mutable more than o
 LL |                    *y = 1;
    |                    ------ first borrow later used here
 
-warning: captured variable cannot escape `FnMut` closure body
+error: captured variable cannot escape `FnMut` closure body
   --> $DIR/borrowck-describe-lvalue.rs:305:16
    |
 LL |              || {
@@ -36,9 +36,6 @@ LL | |                 }
    |
    = note: `FnMut` closures only have access to their captured variables while they are executing...
    = note: ...therefore, they cannot allow references to captured variables to escape
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
 error[E0503]: cannot use `f.x` because it was mutably borrowed
   --> $DIR/borrowck-describe-lvalue.rs:53:9
@@ -382,7 +379,7 @@ LL |                 drop(x); //[ast]~ ERROR use of moved value: `x`
    |
    = note: move occurs because `x` has type `std::vec::Vec<i32>`, which does not implement the `Copy` trait
 
-error: aborting due to 29 previous errors
+error: aborting due to 30 previous errors
 
 Some errors occurred: E0382, E0499, E0502, E0503.
 For more information about an error, try `rustc --explain E0382`.

src/test/ui/borrowck/mutability-errors.nll.stderr

@@ -277,7 +277,7 @@ LL |     &mut x; //~ ERROR
 LL |     &mut x.0; //~ ERROR
    |     ^^^^^^^^ cannot borrow as mutable
 
-warning[E0594]: cannot assign to `x`, as it is not declared as mutable
+error[E0594]: cannot assign to `x`, as it is not declared as mutable
   --> $DIR/mutability-errors.rs:70:9
    |
 LL | fn imm_capture(x: (i32,)) {
@@ -285,12 +285,8 @@ LL | fn imm_capture(x: (i32,)) {
 LL |     || { //~ ERROR
 LL |         x = (1,);
    |         ^^^^^^^^ cannot assign
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
-warning[E0594]: cannot assign to `x.0`, as `x` is not declared as mutable
+error[E0594]: cannot assign to `x.0`, as `x` is not declared as mutable
   --> $DIR/mutability-errors.rs:71:9
    |
 LL | fn imm_capture(x: (i32,)) {
@@ -298,12 +294,8 @@ LL | fn imm_capture(x: (i32,)) {
 ...
 LL |         x.0 = 1;
    |         ^^^^^^^ cannot assign
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
-warning[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
+error[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
   --> $DIR/mutability-errors.rs:72:9
    |
 LL | fn imm_capture(x: (i32,)) {
@@ -311,12 +303,8 @@ LL | fn imm_capture(x: (i32,)) {
 ...
 LL |         &mut x;
    |         ^^^^^^ cannot borrow as mutable
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
-warning[E0596]: cannot borrow `x.0` as mutable, as `x` is not declared as mutable
+error[E0596]: cannot borrow `x.0` as mutable, as `x` is not declared as mutable
   --> $DIR/mutability-errors.rs:73:9
    |
 LL | fn imm_capture(x: (i32,)) {
@@ -324,10 +312,6 @@ LL | fn imm_capture(x: (i32,)) {
 ...
 LL |         &mut x.0;
    |         ^^^^^^^^ cannot borrow as mutable
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
 error[E0594]: cannot assign to `x`, as it is not declared as mutable
   --> $DIR/mutability-errors.rs:76:9
@@ -389,7 +373,7 @@ error[E0596]: cannot borrow `X.0` as mutable, as `X` is an immutable static item
 LL |     &mut X.0; //~ ERROR
    |     ^^^^^^^^ cannot borrow as mutable
 
-error: aborting due to 34 previous errors
+error: aborting due to 38 previous errors
 
 Some errors occurred: E0594, E0596.
 For more information about an error, try `rustc --explain E0594`.

src/test/ui/unboxed-closures/unboxed-closure-immutable-capture.nll.stderr

@@ -33,7 +33,7 @@ LL |     let x = 0;
 LL |     move || set(&mut x); //~ ERROR cannot borrow
    |                 ^^^^^^ cannot borrow as mutable
 
-warning[E0594]: cannot assign to `x`, as it is not declared as mutable
+error[E0594]: cannot assign to `x`, as it is not declared as mutable
   --> $DIR/unboxed-closure-immutable-capture.rs:23:8
    |
 LL |     let x = 0;
@@ -41,12 +41,8 @@ LL |     let x = 0;
 ...
 LL |     || x = 1; //~ ERROR cannot assign
    |        ^^^^^ cannot assign
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
-warning[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
+error[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
   --> $DIR/unboxed-closure-immutable-capture.rs:25:12
    |
 LL |     let x = 0;
@@ -54,12 +50,8 @@ LL |     let x = 0;
 ...
 LL |     || set(&mut x); //~ ERROR cannot assign
    |            ^^^^^^ cannot borrow as mutable
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
-warning[E0594]: cannot assign to `x`, as it is not declared as mutable
+error[E0594]: cannot assign to `x`, as it is not declared as mutable
   --> $DIR/unboxed-closure-immutable-capture.rs:26:8
    |
 LL |     let x = 0;
@@ -67,12 +59,8 @@ LL |     let x = 0;
 ...
 LL |     || x = 1; //~ ERROR cannot assign
    |        ^^^^^ cannot assign
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
-warning[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
+error[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
   --> $DIR/unboxed-closure-immutable-capture.rs:28:12
    |
 LL |     let x = 0;
@@ -80,12 +68,8 @@ LL |     let x = 0;
 ...
 LL |     || set(&mut x); //~ ERROR cannot assign
    |            ^^^^^^ cannot borrow as mutable
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
-error: aborting due to 4 previous errors
+error: aborting due to 8 previous errors
 
 Some errors occurred: E0594, E0596.
 For more information about an error, try `rustc --explain E0594`.

src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-calling-fnmut-no-mut.nll.stderr

@@ -1,4 +1,4 @@
-warning[E0596]: cannot borrow `tick1` as mutable, as it is not declared as mutable
+error[E0596]: cannot borrow `tick1` as mutable, as it is not declared as mutable
   --> $DIR/unboxed-closures-infer-fnmut-calling-fnmut-no-mut.rs:27:9
    |
 LL |     let tick1 = || {
@@ -6,10 +6,6 @@ LL |     let tick1 = || {
 ...
 LL |         tick1();
    |         ^^^^^ cannot borrow as mutable
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
 error[E0596]: cannot borrow `tick2` as mutable, as it is not declared as mutable
   --> $DIR/unboxed-closures-infer-fnmut-calling-fnmut-no-mut.rs:30:5
@@ -20,6 +16,6 @@ LL |     let tick2 = || { //~ ERROR closure cannot assign to immutable local var
 LL |     tick2(); //~ ERROR cannot borrow
    |     ^^^^^ cannot borrow as mutable
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0596`.

src/test/ui/unboxed-closures/unboxed-closures-mutate-upvar.nll.stderr

@@ -1,4 +1,4 @@
-warning[E0594]: cannot assign to `n`, as it is not declared as mutable
+error[E0594]: cannot assign to `n`, as it is not declared as mutable
   --> $DIR/unboxed-closures-mutate-upvar.rs:25:9
    |
 LL |     let n = 0;
@@ -6,10 +6,6 @@ LL |     let n = 0;
 LL |     let mut f = to_fn_mut(|| { //~ ERROR closure cannot assign
 LL |         n += 1;
    |         ^^^^^^ cannot assign
-   |
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
 
 error[E0594]: cannot assign to `n`, as it is not declared as mutable
   --> $DIR/unboxed-closures-mutate-upvar.rs:42:9
@@ -44,6 +40,6 @@ LL | |         n += 1; //~ ERROR cannot assign
 LL | |     });
    | |_____^
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0594`.