Add note to use nightly when using expr in const generics

compiler/rustc_resolve/src/diagnostics.rs

@@ -481,6 +481,7 @@ impl<'a> Resolver<'a> {
                         name
                     ));
                 }
+                err.note("use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions");
 
                 err
             }

src/test/ui/const-generics/array-size-in-generic-struct-param.min.stderr

@@ -5,6 +5,7 @@ LL | struct ArithArrayLen<const N: usize>([u32; 0 + N]);
    |                                                ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/array-size-in-generic-struct-param.rs:20:15
@@ -13,6 +14,7 @@ LL |     arr: [u8; CFG.arr_size],
    |               ^^^ cannot perform const operation using `CFG`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `CFG`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: `Config` is forbidden as the type of a const generic parameter
   --> $DIR/array-size-in-generic-struct-param.rs:18:21

src/test/ui/const-generics/const-arg-in-const-arg.min.stderr

@@ -5,6 +5,7 @@ LL |     let _: [u8; foo::<T>()];
    |                       ^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:15:23
@@ -13,6 +14,7 @@ LL |     let _: [u8; bar::<N>()];
    |                       ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:25:23
@@ -21,6 +23,7 @@ LL |     let _ = [0; bar::<N>()];
    |                       ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:30:24
@@ -29,6 +32,7 @@ LL |     let _: Foo<{ foo::<T>() }>;
    |                        ^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:31:24
@@ -37,6 +41,7 @@ LL |     let _: Foo<{ bar::<N>() }>;
    |                        ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:36:27
@@ -45,6 +50,7 @@ LL |     let _ = Foo::<{ foo::<T>() }>;
    |                           ^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:37:27
@@ -53,6 +59,7 @@ LL |     let _ = Foo::<{ bar::<N>() }>;
    |                           ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error[E0658]: a non-static lifetime is not allowed in a `const`
   --> $DIR/const-arg-in-const-arg.rs:16:23

src/test/ui/const-generics/const-argument-if-length.min.stderr

@@ -5,6 +5,7 @@ LL |     pad: [u8; is_zst::<T>()],
    |                        ^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error[E0277]: the size for values of type `T` cannot be known at compilation time
   --> $DIR/const-argument-if-length.rs:17:12

src/test/ui/const-generics/const_evaluatable_checked/feature-gate-const_evaluatable_checked.min.stderr

@@ -5,6 +5,7 @@ LL | type Arr<const N: usize> = [u8; N - 1];
    |                                 ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to previous error
 

src/test/ui/const-generics/const_evaluatable_checked/simple.min.stderr

@@ -5,6 +5,7 @@ LL | fn test<const N: usize>() -> [u8; N - 1] where [u8; N - 1]: Default {
    |                                                     ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/simple.rs:8:35
@@ -13,6 +14,7 @@ LL | fn test<const N: usize>() -> [u8; N - 1] where [u8; N - 1]: Default {
    |                                   ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/const_evaluatable_checked/simple_fail.min.stderr

@@ -5,6 +5,7 @@ LL | type Arr<const N: usize> = [u8; N - 1];
    |                                 ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to previous error
 

src/test/ui/const-generics/generic-function-call-in-array-length.min.stderr

@@ -5,6 +5,7 @@ LL | fn bar<const N: usize>() -> [u32; foo(N)] {
    |                                       ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/generic-function-call-in-array-length.rs:12:13
@@ -13,6 +14,7 @@ LL |     [0; foo(N)]
    |             ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/generic-sum-in-array-length.min.stderr

@@ -5,6 +5,7 @@ LL | fn foo<const A: usize, const B: usize>(bar: [usize; A + B]) {}
    |                                                     ^ cannot perform const operation using `A`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `A`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/generic-sum-in-array-length.rs:7:57
@@ -13,6 +14,7 @@ LL | fn foo<const A: usize, const B: usize>(bar: [usize; A + B]) {}
    |                                                         ^ cannot perform const operation using `B`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `B`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/intrinsics-type_name-as-const-argument.min.stderr

@@ -5,6 +5,7 @@ LL |     T: Trait<{std::intrinsics::type_name::<T>()}>
    |                                            ^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: `&'static str` is forbidden as the type of a const generic parameter
   --> $DIR/intrinsics-type_name-as-const-argument.rs:10:22

src/test/ui/const-generics/issue-61522-array-len-succ.min.stderr

@@ -5,6 +5,7 @@ LL | pub struct MyArray<const COUNT: usize>([u8; COUNT + 1]);
    |                                             ^^^^^ cannot perform const operation using `COUNT`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `COUNT`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-61522-array-len-succ.rs:12:30
@@ -13,6 +14,7 @@ LL |     fn inner(&self) -> &[u8; COUNT + 1] {
    |                              ^^^^^ cannot perform const operation using `COUNT`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `COUNT`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/issue-67375.min.stderr

@@ -5,6 +5,7 @@ LL |     inner: [(); { [|_: &T| {}; 0].len() }],
    |                         ^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error[E0392]: parameter `T` is never used
   --> $DIR/issue-67375.rs:7:12

src/test/ui/const-generics/issue-67945-1.min.stderr

@@ -5,6 +5,7 @@ LL |         let x: S = MaybeUninit::uninit();
    |                ^ cannot perform const operation using `S`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-67945-1.rs:17:45
@@ -13,6 +14,7 @@ LL |         let b = &*(&x as *const _ as *const S);
    |                                             ^ cannot perform const operation using `S`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error[E0392]: parameter `S` is never used
   --> $DIR/issue-67945-1.rs:11:12

src/test/ui/const-generics/issue-67945-2.min.stderr

@@ -5,6 +5,7 @@ LL |         let x: S = MaybeUninit::uninit();
    |                ^ cannot perform const operation using `S`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-67945-2.rs:15:45
@@ -13,6 +14,7 @@ LL |         let b = &*(&x as *const _ as *const S);
    |                                             ^ cannot perform const operation using `S`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error[E0392]: parameter `S` is never used
   --> $DIR/issue-67945-2.rs:9:12

src/test/ui/const-generics/issues/issue-61747.min.stderr

@@ -5,6 +5,7 @@ LL |     fn successor() -> Const<{C + 1}> {
    |                              ^ cannot perform const operation using `C`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `C`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to previous error
 

src/test/ui/const-generics/issues/issue-61935.min.stderr

@@ -5,6 +5,7 @@ LL |         Self:FooImpl<{N==0}>
    |                       ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to previous error
 

src/test/ui/const-generics/issues/issue-62220.min.stderr

@@ -5,6 +5,7 @@ LL | pub type TruncatedVector<T, const N: usize> = Vector<T, { N - 1 }>;
    |                                                           ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to previous error
 

src/test/ui/const-generics/issues/issue-62456.min.stderr

@@ -5,6 +5,7 @@ LL |     let _ = [0u64; N + 1];
    |                    ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to previous error
 

src/test/ui/const-generics/issues/issue-64494.min.stderr

@@ -5,6 +5,7 @@ LL | impl<T: Foo> MyTrait for T where Is<{T::VAL == 5}>: True {}
    |                                      ^^^^^^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-64494.rs:19:38
@@ -13,6 +14,7 @@ LL | impl<T: Foo> MyTrait for T where Is<{T::VAL == 6}>: True {}
    |                                      ^^^^^^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error[E0119]: conflicting implementations of trait `MyTrait`:
   --> $DIR/issue-64494.rs:19:1

src/test/ui/const-generics/issues/issue-66205.min.stderr

@@ -5,6 +5,7 @@ LL |     fact::<{ N - 1 }>();
    |              ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to previous error
 

src/test/ui/const-generics/issues/issue-68366.min.stderr

@@ -5,6 +5,7 @@ LL | impl <const N: usize> Collatz<{Some(N)}> {}
    |                                     ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
   --> $DIR/issue-68366.rs:12:13

src/test/ui/const-generics/issues/issue-68977.min.stderr

@@ -5,6 +5,7 @@ LL |     PhantomU8<{(INT_BITS + FRAC_BITS + 7) / 8}>;
    |                 ^^^^^^^^ cannot perform const operation using `INT_BITS`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `INT_BITS`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-68977.rs:29:28
@@ -13,6 +14,7 @@ LL |     PhantomU8<{(INT_BITS + FRAC_BITS + 7) / 8}>;
    |                            ^^^^^^^^^ cannot perform const operation using `FRAC_BITS`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `FRAC_BITS`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/issues/issue-72787.min.stderr

@@ -5,6 +5,7 @@ LL |     Condition<{ LHS <= RHS }>: True
    |                 ^^^ cannot perform const operation using `LHS`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `LHS`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-72787.rs:11:24
@@ -13,6 +14,7 @@ LL |     Condition<{ LHS <= RHS }>: True
    |                        ^^^ cannot perform const operation using `RHS`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `RHS`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-72787.rs:26:25
@@ -21,6 +23,7 @@ LL |     IsLessOrEqual<{ 8 - I }, { 8 - J }>: True,
    |                         ^ cannot perform const operation using `I`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `I`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-72787.rs:26:36
@@ -29,6 +32,7 @@ LL |     IsLessOrEqual<{ 8 - I }, { 8 - J }>: True,
    |                                    ^ cannot perform const operation using `J`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `J`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error[E0283]: type annotations needed
   --> $DIR/issue-72787.rs:22:26

src/test/ui/const-generics/issues/issue-72819-generic-in-const-eval.min.stderr

@@ -5,6 +5,7 @@ LL | where Assert::<{N < usize::max_value() / 2}>: IsTrue,
    |                 ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to previous error
 

src/test/ui/const-generics/issues/issue-76701-ty-param-in-const.min.stderr

@@ -5,6 +5,7 @@ LL | fn ty_param<T>() -> [u8; std::mem::size_of::<T>()] {
    |                                              ^ cannot perform const operation using `T`
    |
    = note: type parameters may not be used in const expressions
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: generic parameters may not be used in const operations
   --> $DIR/issue-76701-ty-param-in-const.rs:12:42
@@ -13,6 +14,7 @@ LL | fn const_param<const N: usize>() -> [u8; N + 1] {
    |                                          ^ cannot perform const operation using `N`
    |
    = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = note: use #![feature(const_generics)] and #![feature(const_evaluatable_checked)] to allow generic const expressions
 
 error: aborting due to 2 previous errors