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rust/tests/ui/borrowck/mutability-errors.stderr
Esteban Küber 71b0755a98 Provide more context when mutably borrowing an imutable borrow 
Point at statics and consts being mutable borrowed or written to:

```
error[E0594]: cannot assign to immutable static item `NUM`
  --> $DIR/E0594.rs:4:5
   |
LL | static NUM: i32 = 18;
   | --------------- this `static` cannot be written to
...
LL |     NUM = 20;
   |     ^^^^^^^^ cannot assign
```

Point at the expression that couldn't be mutably borrowed from a pattern:

```
error[E0596]: cannot borrow data in a `&` reference as mutable
  --> $DIR/mut-pattern-of-immutable-borrow.rs:19:14
   |
LL |     match &arg.field {
   |           ---------- this cannot be borrowed as mutable
LL |         Some(ref mut s) => s.push('a'),
   |              ^^^^^^^^^ cannot borrow as mutable
```
2025-11-09 22:14:48 +00:00

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error[E0594]: cannot assign to `*x`, which is behind a `&` reference
--> $DIR/mutability-errors.rs:9:5
|
LL | *x = (1,);
| ^^^^^^^^^ `x` is a `&` reference, so it cannot be written to
|
help: consider changing this to be a mutable reference
|
LL | fn named_ref(x: &mut (i32,)) {
| +++
error[E0594]: cannot assign to `x.0`, which is behind a `&` reference
--> $DIR/mutability-errors.rs:10:5
|
LL | x.0 = 1;
| ^^^^^^^ `x` is a `&` reference, so it cannot be written to
|
help: consider changing this to be a mutable reference
|
LL | fn named_ref(x: &mut (i32,)) {
| +++
error[E0596]: cannot borrow `*x` as mutable, as it is behind a `&` reference
--> $DIR/mutability-errors.rs:11:5
|
LL | &mut *x;
| ^^^^^^^ `x` is a `&` reference, so it cannot be borrowed as mutable
|
help: consider changing this to be a mutable reference
|
LL | fn named_ref(x: &mut (i32,)) {
| +++
error[E0596]: cannot borrow `x.0` as mutable, as it is behind a `&` reference
--> $DIR/mutability-errors.rs:12:5
|
LL | &mut x.0;
| ^^^^^^^^ `x` is a `&` reference, so it cannot be borrowed as mutable
|
help: consider changing this to be a mutable reference
|
LL | fn named_ref(x: &mut (i32,)) {
| +++
error[E0594]: cannot assign to data in a `&` reference
--> $DIR/mutability-errors.rs:16:5
|
LL | *f() = (1,);
| ^^^^^^^^^^^ cannot assign
error[E0594]: cannot assign to data in a `&` reference
--> $DIR/mutability-errors.rs:17:5
|
LL | f().0 = 1;
| ^^^^^^^^^ cannot assign
error[E0596]: cannot borrow data in a `&` reference as mutable
--> $DIR/mutability-errors.rs:18:5
|
LL | &mut *f();
| ^^^^^^^^^ cannot borrow as mutable
error[E0596]: cannot borrow data in a `&` reference as mutable
--> $DIR/mutability-errors.rs:19:5
|
LL | &mut f().0;
| ^^^^^^^^^^ cannot borrow as mutable
error[E0594]: cannot assign to `*x`, which is behind a `*const` pointer
--> $DIR/mutability-errors.rs:23:5
|
LL | *x = (1,);
| ^^^^^^^^^ `x` is a `*const` pointer, so it cannot be written to
|
help: consider changing this to be a mutable pointer
|
LL | unsafe fn named_ptr(x: *mut const (i32,)) {
| +++
error[E0594]: cannot assign to `x.0`, which is behind a `*const` pointer
--> $DIR/mutability-errors.rs:24:5
|
LL | (*x).0 = 1;
| ^^^^^^^^^^ `x` is a `*const` pointer, so it cannot be written to
|
help: consider changing this to be a mutable pointer
|
LL | unsafe fn named_ptr(x: *mut const (i32,)) {
| +++
error[E0596]: cannot borrow `*x` as mutable, as it is behind a `*const` pointer
--> $DIR/mutability-errors.rs:25:5
|
LL | &mut *x;
| ^^^^^^^ `x` is a `*const` pointer, so it cannot be borrowed as mutable
|
help: consider changing this to be a mutable pointer
|
LL | unsafe fn named_ptr(x: *mut const (i32,)) {
| +++
error[E0596]: cannot borrow `x.0` as mutable, as it is behind a `*const` pointer
--> $DIR/mutability-errors.rs:26:5
|
LL | &mut (*x).0;
| ^^^^^^^^^^^ `x` is a `*const` pointer, so it cannot be borrowed as mutable
|
help: consider changing this to be a mutable pointer
|
LL | unsafe fn named_ptr(x: *mut const (i32,)) {
| +++
error[E0594]: cannot assign to data in a `*const` pointer
--> $DIR/mutability-errors.rs:30:5
|
LL | *f() = (1,);
| ^^^^^^^^^^^ cannot assign
error[E0594]: cannot assign to data in a `*const` pointer
--> $DIR/mutability-errors.rs:31:5
|
LL | (*f()).0 = 1;
| ^^^^^^^^^^^^ cannot assign
error[E0596]: cannot borrow data in a `*const` pointer as mutable
--> $DIR/mutability-errors.rs:32:5
|
LL | &mut *f();
| ^^^^^^^^^ cannot borrow as mutable
error[E0596]: cannot borrow data in a `*const` pointer as mutable
--> $DIR/mutability-errors.rs:33:5
|
LL | &mut (*f()).0;
| ^^^^^^^^^^^^^ cannot borrow as mutable
error[E0594]: cannot assign to `x`, as it is a captured variable in a `Fn` closure
--> $DIR/mutability-errors.rs:40:9
|
LL | fn fn_ref<F: Fn()>(f: F) -> F { f }
| - change this to accept `FnMut` instead of `Fn`
LL |
LL | fn ref_closure(mut x: (i32,)) {
| ----- `x` declared here, outside the closure
LL | fn_ref(|| {
| ------ -- in this closure
| |
| expects `Fn` instead of `FnMut`
LL | x = (1,);
| ^^^^^^^^ cannot assign
error[E0594]: cannot assign to `x.0`, as `Fn` closures cannot mutate their captured variables
--> $DIR/mutability-errors.rs:41:9
|
LL | fn fn_ref<F: Fn()>(f: F) -> F { f }
| - change this to accept `FnMut` instead of `Fn`
LL |
LL | fn ref_closure(mut x: (i32,)) {
| ----- `x` declared here, outside the closure
LL | fn_ref(|| {
| ------ -- in this closure
| |
| expects `Fn` instead of `FnMut`
LL | x = (1,);
LL | x.0 = 1;
| ^^^^^^^ cannot assign
error[E0596]: cannot borrow `x` as mutable, as it is a captured variable in a `Fn` closure
--> $DIR/mutability-errors.rs:42:9
|
LL | fn fn_ref<F: Fn()>(f: F) -> F { f }
| - change this to accept `FnMut` instead of `Fn`
LL |
LL | fn ref_closure(mut x: (i32,)) {
| ----- `x` declared here, outside the closure
LL | fn_ref(|| {
| ------ -- in this closure
| |
| expects `Fn` instead of `FnMut`
...
LL | &mut x;
| ^^^^^^ cannot borrow as mutable
error[E0596]: cannot borrow `x.0` as mutable, as `Fn` closures cannot mutate their captured variables
--> $DIR/mutability-errors.rs:43:9
|
LL | fn fn_ref<F: Fn()>(f: F) -> F { f }
| - change this to accept `FnMut` instead of `Fn`
LL |
LL | fn ref_closure(mut x: (i32,)) {
| ----- `x` declared here, outside the closure
LL | fn_ref(|| {
| ------ -- in this closure
| |
| expects `Fn` instead of `FnMut`
...
LL | &mut x.0;
| ^^^^^^^^ cannot borrow as mutable
error[E0594]: cannot assign to `x`, as it is a captured variable in a `Fn` closure
--> $DIR/mutability-errors.rs:46:9
|
LL | fn fn_ref<F: Fn()>(f: F) -> F { f }
| - change this to accept `FnMut` instead of `Fn`
...
LL | fn_ref(move || {
| ------ ------- in this closure
| |
| expects `Fn` instead of `FnMut`
LL | x = (1,);
| ^^^^^^^^ cannot assign
error[E0594]: cannot assign to `x.0`, as `Fn` closures cannot mutate their captured variables
--> $DIR/mutability-errors.rs:47:9
|
LL | fn fn_ref<F: Fn()>(f: F) -> F { f }
| - change this to accept `FnMut` instead of `Fn`
...
LL | fn_ref(move || {
| ------ ------- in this closure
| |
| expects `Fn` instead of `FnMut`
LL | x = (1,);
LL | x.0 = 1;
| ^^^^^^^ cannot assign
error[E0596]: cannot borrow `x` as mutable, as it is a captured variable in a `Fn` closure
--> $DIR/mutability-errors.rs:48:9
|
LL | fn fn_ref<F: Fn()>(f: F) -> F { f }
| - change this to accept `FnMut` instead of `Fn`
...
LL | fn_ref(move || {
| ------ ------- in this closure
| |
| expects `Fn` instead of `FnMut`
...
LL | &mut x;
| ^^^^^^ cannot borrow as mutable
error[E0596]: cannot borrow `x.0` as mutable, as `Fn` closures cannot mutate their captured variables
--> $DIR/mutability-errors.rs:49:9
|
LL | fn fn_ref<F: Fn()>(f: F) -> F { f }
| - change this to accept `FnMut` instead of `Fn`
...
LL | fn_ref(move || {
| ------ ------- in this closure
| |
| expects `Fn` instead of `FnMut`
...
LL | &mut x.0;
| ^^^^^^^^ cannot borrow as mutable
error[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
--> $DIR/mutability-errors.rs:53:14
|
LL | fn imm_local(x: (i32,)) {
| ^ not mutable
LL | &mut x;
| ------ cannot borrow as mutable
LL | &mut x.0;
| -------- cannot borrow as mutable
|
help: consider changing this to be mutable
|
LL | fn imm_local(mut x: (i32,)) {
| +++
error[E0594]: cannot assign to `x`, as it is not declared as mutable
--> $DIR/mutability-errors.rs:60:9
|
LL | x = (1,);
| ^^^^^^^^ cannot assign
|
help: consider changing this to be mutable
|
LL | fn imm_capture(mut x: (i32,)) {
| +++
error[E0594]: cannot assign to `x.0`, as `x` is not declared as mutable
--> $DIR/mutability-errors.rs:61:9
|
LL | x.0 = 1;
| ^^^^^^^ cannot assign
|
help: consider changing this to be mutable
|
LL | fn imm_capture(mut x: (i32,)) {
| +++
error[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
--> $DIR/mutability-errors.rs:62:9
|
LL | &mut x;
| ^^^^^^ cannot borrow as mutable
|
help: consider changing this to be mutable
|
LL | fn imm_capture(mut x: (i32,)) {
| +++
error[E0596]: cannot borrow `x.0` as mutable, as `x` is not declared as mutable
--> $DIR/mutability-errors.rs:63:9
|
LL | &mut x.0;
| ^^^^^^^^ cannot borrow as mutable
|
help: consider changing this to be mutable
|
LL | fn imm_capture(mut x: (i32,)) {
| +++
error[E0594]: cannot assign to `x`, as it is not declared as mutable
--> $DIR/mutability-errors.rs:66:9
|
LL | x = (1,);
| ^^^^^^^^ cannot assign
|
help: consider changing this to be mutable
|
LL | fn imm_capture(mut x: (i32,)) {
| +++
error[E0594]: cannot assign to `x.0`, as `x` is not declared as mutable
--> $DIR/mutability-errors.rs:67:9
|
LL | x.0 = 1;
| ^^^^^^^ cannot assign
|
help: consider changing this to be mutable
|
LL | fn imm_capture(mut x: (i32,)) {
| +++
error[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
--> $DIR/mutability-errors.rs:68:9
|
LL | &mut x;
| ^^^^^^ cannot borrow as mutable
|
help: consider changing this to be mutable
|
LL | fn imm_capture(mut x: (i32,)) {
| +++
error[E0596]: cannot borrow `x.0` as mutable, as `x` is not declared as mutable
--> $DIR/mutability-errors.rs:69:9
|
LL | &mut x.0;
| ^^^^^^^^ cannot borrow as mutable
|
help: consider changing this to be mutable
|
LL | fn imm_capture(mut x: (i32,)) {
| +++
error[E0594]: cannot assign to immutable static item `X`
--> $DIR/mutability-errors.rs:76:5
|
LL | static X: (i32,) = (0,);
| ---------------- this `static` cannot be written to
...
LL | X = (1,);
| ^^^^^^^^ cannot assign
error[E0594]: cannot assign to `X.0`, as `X` is an immutable static item
--> $DIR/mutability-errors.rs:77:5
|
LL | static X: (i32,) = (0,);
| ---------------- this `static` cannot be written to
...
LL | X.0 = 1;
| ^^^^^^^ cannot assign
error[E0596]: cannot borrow immutable static item `X` as mutable
--> $DIR/mutability-errors.rs:78:5
|
LL | static X: (i32,) = (0,);
| ---------------- this `static` cannot be borrowed as mutable
...
LL | &mut X;
| ^^^^^^ cannot borrow as mutable
error[E0596]: cannot borrow `X.0` as mutable, as `X` is an immutable static item
--> $DIR/mutability-errors.rs:79:5
|
LL | static X: (i32,) = (0,);
| ---------------- this `static` cannot be borrowed as mutable
...
LL | &mut X.0;
| ^^^^^^^^ cannot borrow as mutable
error: aborting due to 37 previous errors
Some errors have detailed explanations: E0594, E0596.
For more information about an error, try `rustc --explain E0594`.
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