Add note to use nightly when using expr in const generics

compiler/rustc_resolve/src/diagnostics.rs

@@ -480,6 +480,7 @@ impl<'a> Resolver<'a> {
                         "const parameters may only be used as standalone arguments, i.e. `{}`",
                         name
                     ));
+                    err.note("use feature(const_generics) and feature(const_evaluatable_checked) to enable this");
                 }
 
                 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 enable this
 
 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 enable this
 
 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

@@ -13,6 +13,7 @@ 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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:25:23
@@ -21,6 +22,7 @@ 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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:30:24
@@ -37,6 +39,7 @@ 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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/const-arg-in-const-arg.rs:36:27
@@ -53,6 +56,7 @@ 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 enable this
 
 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_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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 error: aborting due to 2 previous errors
 

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 enable this
 
 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 enable this
 
 error: aborting due to 2 previous errors
 

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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 error: aborting due to previous error
 

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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 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 enable this
 
 error: aborting due to previous error
 

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

@@ -13,6 +13,7 @@ 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 enable this
 
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/macro_rules-braces.min.stderr

@@ -27,6 +27,7 @@ LL |     let _: 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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/macro_rules-braces.rs:41:19
@@ -35,6 +36,7 @@ LL |     let _: 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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/macro_rules-braces.rs:46:20
@@ -43,6 +45,7 @@ LL |     let _: baz!({{ 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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/macro_rules-braces.rs:51:19
@@ -51,6 +54,7 @@ LL |     let _: biz!({ 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 enable this
 
 error: aborting due to 6 previous errors
 

src/test/ui/const-generics/min_const_generics/complex-expression.stderr

@@ -5,6 +5,7 @@ LL | struct Break0<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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/complex-expression.rs:14:40
@@ -13,6 +14,7 @@ LL | struct Break1<const N: usize>([u8; { { 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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/complex-expression.rs:18:17
@@ -21,6 +23,7 @@ LL |     let _: [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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/complex-expression.rs:23:17
@@ -29,6 +32,7 @@ LL |     let _ = [0; 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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/complex-expression.rs:27:45

src/test/ui/const-generics/wf-misc.min.stderr

@@ -5,6 +5,7 @@ LL |     let _: [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 enable this
 
 error: generic parameters may not be used in const operations
   --> $DIR/wf-misc.rs:17:21
@@ -13,6 +14,7 @@ LL |     let _: Const::<{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 enable this
 
 error: aborting due to 2 previous errors