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add new error code
1 parent 1f48465 commit 96031e2

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lines changed

‎src/librustc_error_codes/error_codes.rs

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@@ -444,6 +444,7 @@ E0760: include_str!("./error_codes/E0760.md"),
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E0761: include_str!("./error_codes/E0761.md"),
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E0762: include_str!("./error_codes/E0762.md"),
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E0763: include_str!("./error_codes/E0763.md"),
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E0764: include_str!("./error_codes/E0764.md"),
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;
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// E0006, // merged with E0005
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// E0008, // cannot bind by-move into a pattern guard

‎src/librustc_error_codes/error_codes/E0764.md

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Mutable references (`&mut`) can only be used in constant functions, not statics
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or constants. This limitation exists to prevent the creation of constants that
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have a mutable reference in their final value. If you had a constant of `&mut
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i32` type, you could modify the value through that reference, making the
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constant essentially mutable. While there could be a more fine-grained scheme
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in the future that allows mutable references if they are not "leaked" to the
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final value, a more conservative approach was chosen for now. `const fn` do not
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have this problem, as the borrow checker will prevent the `const fn` from
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returning new mutable references.
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Erroneous code example:
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```compile_fail,E0764
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#![feature(const_fn)]
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#![feature(const_mut_refs)]
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fn main() {
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const OH_NO: &'static mut usize = &mut 1; // error!
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}
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```
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Remember: you cannot use a function call inside a constant or static. However,
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you can totally use it in constant functions:
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```
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#![feature(const_fn)]
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#![feature(const_mut_refs)]
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const fn foo(x: usize) -> usize {
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let mut y = 1;
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let z = &mut y;
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*z += x;
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y
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}
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fn main() {
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const FOO: usize = foo(10); // ok!
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}
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```

‎src/librustc_mir/transform/check_consts/ops.rs

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@@ -227,7 +227,7 @@ impl NonConstOp for MutBorrow {
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struct_span_err!(
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ccx.tcx.sess,
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span,
230-
E0019,
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E0764,
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"mutable references are not allowed in {}s",
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ccx.const_kind(),
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)

‎src/test/ui/check-static-immutable-mut-slices.stderr

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@@ -1,9 +1,9 @@
1-
error[E0019]: mutable references are not allowed in statics
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error[E0764]: mutable references are not allowed in statics
22
--> $DIR/check-static-immutable-mut-slices.rs:3:37
33
|
44
LL | static TEST: &'static mut [isize] = &mut [];
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| ^^^^^^^ `&mut` is only allowed in `const fn`
66

77
error: aborting due to previous error
88

9-
For more information about this error, try `rustc --explain E0019`.
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For more information about this error, try `rustc --explain E0764`.

‎src/test/ui/consts/const-eval/issue-65394.stderr

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@@ -1,4 +1,4 @@
1-
error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/issue-65394.rs:8:13
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|
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LL | let r = &mut x;
@@ -12,5 +12,5 @@ LL | let mut x = Vec::<i32>::new();
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error: aborting due to 2 previous errors
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Some errors have detailed explanations: E0019, E0493.
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For more information about an error, try `rustc --explain E0019`.
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Some errors have detailed explanations: E0493, E0764.
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For more information about an error, try `rustc --explain E0493`.

‎src/test/ui/consts/const-multi-ref.stderr

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@@ -1,4 +1,4 @@
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error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/const-multi-ref.rs:6:13
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|
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LL | let p = &mut a;
@@ -12,5 +12,5 @@ LL | let p = &a;
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error: aborting due to 2 previous errors
1414

15-
Some errors have detailed explanations: E0019, E0492.
16-
For more information about an error, try `rustc --explain E0019`.
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Some errors have detailed explanations: E0492, E0764.
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For more information about an error, try `rustc --explain E0492`.

‎src/test/ui/consts/const-mut-refs/const_mut_address_of.stderr

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@@ -1,15 +1,15 @@
1-
error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/const_mut_address_of.rs:24:5
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|
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LL | foo().bar();
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| ^^^^^ `&mut` is only allowed in `const fn`
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error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/const_mut_address_of.rs:26:9
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|
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LL | baz(&mut foo());
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| ^^^^^^^^^^ `&mut` is only allowed in `const fn`
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1313
error: aborting due to 2 previous errors
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15-
For more information about this error, try `rustc --explain E0019`.
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For more information about this error, try `rustc --explain E0764`.

‎src/test/ui/consts/const-mut-refs/const_mut_refs.stderr

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@@ -1,21 +1,21 @@
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error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/const_mut_refs.rs:31:17
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|
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LL | let _: [(); foo().bar()] = [(); 1];
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| ^^^^^ `&mut` is only allowed in `const fn`
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error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/const_mut_refs.rs:33:21
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|
1010
LL | let _: [(); baz(&mut foo())] = [(); 2];
1111
| ^^^^^^^^^^ `&mut` is only allowed in `const fn`
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13-
error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/const_mut_refs.rs:35:22
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|
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LL | let _: [(); bazz(&mut foo())] = [(); 3];
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| ^^^^^^^^^^ `&mut` is only allowed in `const fn`
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error: aborting due to 3 previous errors
2020

21-
For more information about this error, try `rustc --explain E0019`.
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For more information about this error, try `rustc --explain E0764`.

‎src/test/ui/consts/const_let_assign3.stderr

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@@ -6,13 +6,13 @@ LL | self.state = x;
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|
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= help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
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9-
error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/const_let_assign3.rs:16:5
1111
|
1212
LL | s.foo(3);
1313
| ^ `&mut` is only allowed in `const fn`
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15-
error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/const_let_assign3.rs:22:13
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|
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LL | let y = &mut x;
@@ -28,4 +28,5 @@ LL | *y = 42;
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2929
error: aborting due to 4 previous errors
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31-
For more information about this error, try `rustc --explain E0019`.
31+
Some errors have detailed explanations: E0019, E0764.
32+
For more information about an error, try `rustc --explain E0019`.

‎src/test/ui/consts/projection_qualif.mut_refs.stderr

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@@ -1,4 +1,4 @@
1-
error[E0019]: mutable references are not allowed in constants
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error[E0764]: mutable references are not allowed in constants
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--> $DIR/projection_qualif.rs:10:27
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|
44
LL | let b: *mut u32 = &mut a;
@@ -15,5 +15,5 @@ LL | unsafe { *b = 5; }
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1616
error: aborting due to 2 previous errors
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18-
Some errors have detailed explanations: E0019, E0658.
19-
For more information about an error, try `rustc --explain E0019`.
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Some errors have detailed explanations: E0658, E0764.
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For more information about an error, try `rustc --explain E0658`.

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