Add note to use nightly when using expr in const generics

Author: mendess

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