Rollup merge of #137617 - BoxyUwU:generic_const_parameter_types, r=lcnr

Introduce `feature(generic_const_parameter_types)`

Allows to define const generic parameters whose type depends on other generic parameters, e.g. `Foo<const N: usize, const ARR: [u8; N]>;`

Wasn't going to implement for this for a while until we could implement it with `bad_inference.rs` resolved but apparently the project simd folks would like to be able to use this for some intrinsics and the inference issue isn't really a huge problem there aiui. (cc ``@workingjubilee`` )

37 files changed, 271 insertions, 53 deletions

diff --git a/tests/ui/const-generics/const-param-type-depends-on-const-param.full.stderr b/tests/ui/const-generics/const-param-type-depends-on-const-param.full.stderr
index 539d840f0a8..f639e276f46 100644
--- a/tests/ui/const-generics/const-param-type-depends-on-const-param.full.stderr
+++ b/tests/ui/const-generics/const-param-type-depends-on-const-param.full.stderr
@@ -3,16 +3,12 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | pub struct Dependent<const N: usize, const X: [u8; N]>([(); N]);
    |                                                    ^ the type must not depend on the parameter `N`
-   |
-   = note: const parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
   --> $DIR/const-param-type-depends-on-const-param.rs:15:40
    |
 LL | pub struct SelfDependent<const N: [u8; N]>;
    |                                        ^ the type must not depend on the parameter `N`
-   |
-   = note: const parameters may not be used in the type of const parameters
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/const-generics/const-param-type-depends-on-const-param.min.stderr b/tests/ui/const-generics/const-param-type-depends-on-const-param.min.stderr
index 18b89963267..44fcf9a13b1 100644
--- a/tests/ui/const-generics/const-param-type-depends-on-const-param.min.stderr
+++ b/tests/ui/const-generics/const-param-type-depends-on-const-param.min.stderr
@@ -3,16 +3,12 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | pub struct Dependent<const N: usize, const X: [u8; N]>([(); N]);
    |                                                    ^ the type must not depend on the parameter `N`
-   |
-   = note: const parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
   --> $DIR/const-param-type-depends-on-const-param.rs:15:40
    |
 LL | pub struct SelfDependent<const N: [u8; N]>;
    |                                        ^ the type must not depend on the parameter `N`
-   |
-   = note: const parameters may not be used in the type of const parameters
 
 error: `[u8; N]` is forbidden as the type of a const generic parameter
   --> $DIR/const-param-type-depends-on-const-param.rs:11:47
diff --git a/tests/ui/const-generics/const-param-type-depends-on-type-param-ungated.stderr b/tests/ui/const-generics/const-param-type-depends-on-type-param-ungated.stderr
index 55bced29aff..3075597895b 100644
--- a/tests/ui/const-generics/const-param-type-depends-on-type-param-ungated.stderr
+++ b/tests/ui/const-generics/const-param-type-depends-on-type-param-ungated.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | struct B<T, const N: T>(PhantomData<[T; N]>);
    |                      ^ the type must not depend on the parameter `T`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/const-generics/const-param-type-depends-on-type-param.full.stderr b/tests/ui/const-generics/const-param-type-depends-on-type-param.full.stderr
index 49cf4281323..e8257ace692 100644
--- a/tests/ui/const-generics/const-param-type-depends-on-type-param.full.stderr
+++ b/tests/ui/const-generics/const-param-type-depends-on-type-param.full.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | pub struct Dependent<T, const X: T>([(); X]);
    |                                  ^ the type must not depend on the parameter `T`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error[E0392]: type parameter `T` is never used
   --> $DIR/const-param-type-depends-on-type-param.rs:11:22
diff --git a/tests/ui/const-generics/const-param-type-depends-on-type-param.min.stderr b/tests/ui/const-generics/const-param-type-depends-on-type-param.min.stderr
index 49cf4281323..e8257ace692 100644
--- a/tests/ui/const-generics/const-param-type-depends-on-type-param.min.stderr
+++ b/tests/ui/const-generics/const-param-type-depends-on-type-param.min.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | pub struct Dependent<T, const X: T>([(); X]);
    |                                  ^ the type must not depend on the parameter `T`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error[E0392]: type parameter `T` is never used
   --> $DIR/const-param-type-depends-on-type-param.rs:11:22
diff --git a/tests/ui/const-generics/generic_const_parameter_types/bad_inference.rs b/tests/ui/const-generics/generic_const_parameter_types/bad_inference.rs
new file mode 100644
index 00000000000..de2e687e870
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/bad_inference.rs
@@ -0,0 +1,23 @@
+#![feature(
+    adt_const_params,
+    unsized_const_params,
+    generic_const_parameter_types,
+    generic_arg_infer
+)]
+#![allow(incomplete_features)]
+
+use std::marker::ConstParamTy_;
+
+fn foo<T: ConstParamTy_, const N: usize, const M: [T; N]>() -> [T; N] {
+    loop {}
+}
+
+fn main() {
+    // Requires inferring `T`/`N` from `12_u8` and `2` respectively.
+    let a = foo::<_, _, { [12_u8; 2] }>();
+    //~^ ERROR: anonymous constants with inferred types are not yet supported
+
+    // Requires inferring `T`/`N`/`12_?i`/`_` from `[u8; 2]`
+    let b: [u8; 2] = foo::<_, _, { [12; _] }>();
+    //~^ ERROR: anonymous constants with inferred types are not yet supported
+}
diff --git a/tests/ui/const-generics/generic_const_parameter_types/bad_inference.stderr b/tests/ui/const-generics/generic_const_parameter_types/bad_inference.stderr
new file mode 100644
index 00000000000..1ac67fe622b
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/bad_inference.stderr
@@ -0,0 +1,14 @@
+error: anonymous constants with inferred types are not yet supported
+  --> $DIR/bad_inference.rs:17:25
+   |
+LL |     let a = foo::<_, _, { [12_u8; 2] }>();
+   |                         ^^^^^^^^^^^^^^
+
+error: anonymous constants with inferred types are not yet supported
+  --> $DIR/bad_inference.rs:21:34
+   |
+LL |     let b: [u8; 2] = foo::<_, _, { [12; _] }>();
+   |                                  ^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
diff --git a/tests/ui/const-generics/generic_const_parameter_types/evaluate_const_parameter_in_mir.rs b/tests/ui/const-generics/generic_const_parameter_types/evaluate_const_parameter_in_mir.rs
new file mode 100644
index 00000000000..910deb6632d
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/evaluate_const_parameter_in_mir.rs
@@ -0,0 +1,19 @@
+//@ check-pass
+
+#![feature(
+    adt_const_params,
+    unsized_const_params,
+    generic_const_parameter_types,
+    generic_arg_infer
+)]
+#![allow(incomplete_features)]
+
+use std::marker::ConstParamTy_;
+
+fn foo<T: ConstParamTy_, const N: usize, const M: [T; N]>() -> [T; N] {
+    M
+}
+
+fn main() {
+    let a: [u8; 2] = foo::<u8, 2, { [12; _] }>();
+}
diff --git a/tests/ui/const-generics/generic_const_parameter_types/forward_declared_type.rs b/tests/ui/const-generics/generic_const_parameter_types/forward_declared_type.rs
new file mode 100644
index 00000000000..91c1c80e07c
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/forward_declared_type.rs
@@ -0,0 +1,11 @@
+#![feature(adt_const_params, generic_const_parameter_types)]
+#![expect(incomplete_features)]
+
+use std::marker::PhantomData;
+
+struct UsesConst<const N: [u8; M], const M: usize>;
+//~^ ERROR: the type of const parameters must not depend on other generic parameters
+struct UsesType<const N: [T; 2], T>(PhantomData<T>);
+//~^ ERROR: the type of const parameters must not depend on other generic parameters
+
+fn main() {}
diff --git a/tests/ui/const-generics/generic_const_parameter_types/forward_declared_type.stderr b/tests/ui/const-generics/generic_const_parameter_types/forward_declared_type.stderr
new file mode 100644
index 00000000000..b0dbdff8413
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/forward_declared_type.stderr
@@ -0,0 +1,15 @@
+error[E0770]: the type of const parameters must not depend on other generic parameters
+  --> $DIR/forward_declared_type.rs:6:32
+   |
+LL | struct UsesConst<const N: [u8; M], const M: usize>;
+   |                                ^ the type must not depend on the parameter `M`
+
+error[E0770]: the type of const parameters must not depend on other generic parameters
+  --> $DIR/forward_declared_type.rs:8:27
+   |
+LL | struct UsesType<const N: [T; 2], T>(PhantomData<T>);
+   |                           ^ the type must not depend on the parameter `T`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0770`.
diff --git a/tests/ui/const-generics/generic_const_parameter_types/inferred_from_arg.rs b/tests/ui/const-generics/generic_const_parameter_types/inferred_from_arg.rs
new file mode 100644
index 00000000000..d655fc174ee
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/inferred_from_arg.rs
@@ -0,0 +1,13 @@
+//@ check-pass
+
+#![feature(adt_const_params, generic_arg_infer, generic_const_parameter_types)]
+#![expect(incomplete_features)]
+
+struct Bar<const N: usize, const M: [u8; N]>;
+
+fn foo<const N: usize, const M: [u8; N]>(_: Bar<N, M>) {}
+
+fn main() {
+    foo(Bar::<2, { [1; 2] }>);
+    foo::<_, _>(Bar::<2, { [1; 2] }>);
+}
diff --git a/tests/ui/const-generics/generic_const_parameter_types/lifetime_dependent_const_param.rs b/tests/ui/const-generics/generic_const_parameter_types/lifetime_dependent_const_param.rs
new file mode 100644
index 00000000000..6b81ca743aa
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/lifetime_dependent_const_param.rs
@@ -0,0 +1,20 @@
+#![feature(generic_const_parameter_types, adt_const_params, unsized_const_params)]
+#![expect(incomplete_features)]
+
+fn foo<'a, const N: &'a u32>() {}
+
+fn bar() {
+    foo::<'static, { &1_u32 }>();
+    //~^ ERROR: anonymous constants with lifetimes in their type are not yet supported
+    foo::<'_, { &1_u32 }>();
+    //~^ ERROR: anonymous constants with lifetimes in their type are not yet supported
+}
+
+fn borrowck<'a, const N: &'static u32, const M: &'a u32>() {
+    foo::<'a, M>();
+    foo::<'static, M>();
+    //~^ ERROR: lifetime may not live long enough
+    foo::<'static, N>();
+}
+
+fn main() {}
diff --git a/tests/ui/const-generics/generic_const_parameter_types/lifetime_dependent_const_param.stderr b/tests/ui/const-generics/generic_const_parameter_types/lifetime_dependent_const_param.stderr
new file mode 100644
index 00000000000..be5f27bcbc0
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/lifetime_dependent_const_param.stderr
@@ -0,0 +1,23 @@
+error: anonymous constants with lifetimes in their type are not yet supported
+  --> $DIR/lifetime_dependent_const_param.rs:7:20
+   |
+LL |     foo::<'static, { &1_u32 }>();
+   |                    ^^^^^^^^^^
+
+error: anonymous constants with lifetimes in their type are not yet supported
+  --> $DIR/lifetime_dependent_const_param.rs:9:15
+   |
+LL |     foo::<'_, { &1_u32 }>();
+   |               ^^^^^^^^^^
+
+error: lifetime may not live long enough
+  --> $DIR/lifetime_dependent_const_param.rs:15:5
+   |
+LL | fn borrowck<'a, const N: &'static u32, const M: &'a u32>() {
+   |             -- lifetime `'a` defined here
+LL |     foo::<'a, M>();
+LL |     foo::<'static, M>();
+   |     ^^^^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
+
+error: aborting due to 3 previous errors
+
diff --git a/tests/ui/const-generics/generic_const_parameter_types/mismatched_args_with_value.rs b/tests/ui/const-generics/generic_const_parameter_types/mismatched_args_with_value.rs
new file mode 100644
index 00000000000..df8a057b335
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/mismatched_args_with_value.rs
@@ -0,0 +1,15 @@
+#![feature(adt_const_params, unsized_const_params, generic_const_parameter_types)]
+#![allow(incomplete_features)]
+
+use std::marker::ConstParamTy_;
+
+fn foo<const N: usize, const M: [u8; N]>() {}
+fn bar<T: ConstParamTy_, const M: [T; 2]>() {}
+
+fn main() {
+    foo::<3, { [1; 2] }>();
+    //~^ ERROR: mismatched type
+
+    bar::<u8, { [2_u16; 2] }>();
+    //~^ ERROR: mismatched type
+}
diff --git a/tests/ui/const-generics/generic_const_parameter_types/mismatched_args_with_value.stderr b/tests/ui/const-generics/generic_const_parameter_types/mismatched_args_with_value.stderr
new file mode 100644
index 00000000000..2411d31b980
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/mismatched_args_with_value.stderr
@@ -0,0 +1,21 @@
+error[E0308]: mismatched types
+  --> $DIR/mismatched_args_with_value.rs:10:16
+   |
+LL |     foo::<3, { [1; 2] }>();
+   |                ^^^^^^ expected an array with a size of 3, found one with a size of 2
+
+error[E0308]: mismatched types
+  --> $DIR/mismatched_args_with_value.rs:13:18
+   |
+LL |     bar::<u8, { [2_u16; 2] }>();
+   |                  ^^^^^ expected `u8`, found `u16`
+   |
+help: change the type of the numeric literal from `u16` to `u8`
+   |
+LL -     bar::<u8, { [2_u16; 2] }>();
+LL +     bar::<u8, { [2_u8; 2] }>();
+   |
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/const-generics/generic_const_parameter_types/no_const_param_ty_bound.rs b/tests/ui/const-generics/generic_const_parameter_types/no_const_param_ty_bound.rs
new file mode 100644
index 00000000000..1a5ab46cda1
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/no_const_param_ty_bound.rs
@@ -0,0 +1,9 @@
+#![feature(adt_const_params, unsized_const_params, generic_const_parameter_types)]
+#![expect(incomplete_features)]
+
+use std::marker::{ConstParamTy_, PhantomData};
+
+struct UsesType<T, const N: usize, const M: [T; N]>(PhantomData<T>);
+//~^ ERROR: `[T; N]` can't be used as a const parameter type
+
+fn main() {}
diff --git a/tests/ui/const-generics/generic_const_parameter_types/no_const_param_ty_bound.stderr b/tests/ui/const-generics/generic_const_parameter_types/no_const_param_ty_bound.stderr
new file mode 100644
index 00000000000..4ea323f4a5c
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/no_const_param_ty_bound.stderr
@@ -0,0 +1,11 @@
+error[E0741]: `[T; N]` can't be used as a const parameter type
+  --> $DIR/no_const_param_ty_bound.rs:6:45
+   |
+LL | struct UsesType<T, const N: usize, const M: [T; N]>(PhantomData<T>);
+   |                                             ^^^^^^
+   |
+   = note: `T` must implement `UnsizedConstParamTy`, but it does not
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0741`.
diff --git a/tests/ui/const-generics/generic_const_parameter_types/unrelated_inferred_arg.rs b/tests/ui/const-generics/generic_const_parameter_types/unrelated_inferred_arg.rs
new file mode 100644
index 00000000000..b389e12884e
--- /dev/null
+++ b/tests/ui/const-generics/generic_const_parameter_types/unrelated_inferred_arg.rs
@@ -0,0 +1,21 @@
+//@ check-pass
+
+#![feature(
+    adt_const_params,
+    unsized_const_params,
+    generic_const_parameter_types,
+    generic_arg_infer
+)]
+#![allow(incomplete_features)]
+
+use std::marker::ConstParamTy_;
+
+fn foo<U, T: ConstParamTy_, const N: usize, const M: [T; N]>(_: U) -> [T; N] {
+    loop {}
+}
+
+fn main() {
+    // Check that `_` doesnt cause a "Type of const argument is uninferred" error
+    // as it is not actually used by the type of `M`.
+    let a = foo::<_, u8, 2, { [12; _] }>(true);
+}
diff --git a/tests/ui/const-generics/issues/issue-56445-1.full.stderr b/tests/ui/const-generics/issues/issue-56445-1.full.stderr
index 86eb57355bd..392a125de67 100644
--- a/tests/ui/const-generics/issues/issue-56445-1.full.stderr
+++ b/tests/ui/const-generics/issues/issue-56445-1.full.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | struct Bug<'a, const S: &'a str>(PhantomData<&'a ()>);
    |                          ^^ the type must not depend on the parameter `'a`
-   |
-   = note: lifetime parameters may not be used in the type of const parameters
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/const-generics/issues/issue-56445-1.min.stderr b/tests/ui/const-generics/issues/issue-56445-1.min.stderr
index 86eb57355bd..392a125de67 100644
--- a/tests/ui/const-generics/issues/issue-56445-1.min.stderr
+++ b/tests/ui/const-generics/issues/issue-56445-1.min.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | struct Bug<'a, const S: &'a str>(PhantomData<&'a ()>);
    |                          ^^ the type must not depend on the parameter `'a`
-   |
-   = note: lifetime parameters may not be used in the type of const parameters
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/const-generics/issues/issue-62878.full.stderr b/tests/ui/const-generics/issues/issue-62878.full.stderr
index 615bfeb65a5..5e6b3ad9f4c 100644
--- a/tests/ui/const-generics/issues/issue-62878.full.stderr
+++ b/tests/ui/const-generics/issues/issue-62878.full.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | fn foo<const N: usize, const A: [u8; N]>() {}
    |                                      ^ the type must not depend on the parameter `N`
-   |
-   = note: const parameters may not be used in the type of const parameters
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/const-generics/issues/issue-62878.min.stderr b/tests/ui/const-generics/issues/issue-62878.min.stderr
index 1bb111b188d..d3d4fa43871 100644
--- a/tests/ui/const-generics/issues/issue-62878.min.stderr
+++ b/tests/ui/const-generics/issues/issue-62878.min.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | fn foo<const N: usize, const A: [u8; N]>() {}
    |                                      ^ the type must not depend on the parameter `N`
-   |
-   = note: const parameters may not be used in the type of const parameters
 
 error: `[u8; N]` is forbidden as the type of a const generic parameter
   --> $DIR/issue-62878.rs:5:33
diff --git a/tests/ui/const-generics/issues/issue-71169.full.stderr b/tests/ui/const-generics/issues/issue-71169.full.stderr
index 9553be6fc07..f600ecdab74 100644
--- a/tests/ui/const-generics/issues/issue-71169.full.stderr
+++ b/tests/ui/const-generics/issues/issue-71169.full.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | fn foo<const LEN: usize, const DATA: [u8; LEN]>() {}
    |                                           ^^^ the type must not depend on the parameter `LEN`
-   |
-   = note: const parameters may not be used in the type of const parameters
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/const-generics/issues/issue-71169.min.stderr b/tests/ui/const-generics/issues/issue-71169.min.stderr
index 2ecbc337951..c04a710eee9 100644
--- a/tests/ui/const-generics/issues/issue-71169.min.stderr
+++ b/tests/ui/const-generics/issues/issue-71169.min.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | fn foo<const LEN: usize, const DATA: [u8; LEN]>() {}
    |                                           ^^^ the type must not depend on the parameter `LEN`
-   |
-   = note: const parameters may not be used in the type of const parameters
 
 error: `[u8; LEN]` is forbidden as the type of a const generic parameter
   --> $DIR/issue-71169.rs:5:38
diff --git a/tests/ui/const-generics/issues/issue-71381.full.stderr b/tests/ui/const-generics/issues/issue-71381.full.stderr
index b6460e0017f..01bbe55415d 100644
--- a/tests/ui/const-generics/issues/issue-71381.full.stderr
+++ b/tests/ui/const-generics/issues/issue-71381.full.stderr
@@ -3,16 +3,12 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL |     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "C" fn(Args)>(&self) {
    |                                                                                  ^^^^ the type must not depend on the parameter `Args`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
   --> $DIR/issue-71381.rs:23:40
    |
 LL |         const FN: unsafe extern "C" fn(Args),
    |                                        ^^^^ the type must not depend on the parameter `Args`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/const-generics/issues/issue-71381.min.stderr b/tests/ui/const-generics/issues/issue-71381.min.stderr
index 38d2cbe6368..2b0a671bc3f 100644
--- a/tests/ui/const-generics/issues/issue-71381.min.stderr
+++ b/tests/ui/const-generics/issues/issue-71381.min.stderr
@@ -3,16 +3,12 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL |     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "C" fn(Args)>(&self) {
    |                                                                                  ^^^^ the type must not depend on the parameter `Args`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
   --> $DIR/issue-71381.rs:23:40
    |
 LL |         const FN: unsafe extern "C" fn(Args),
    |                                        ^^^^ the type must not depend on the parameter `Args`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error: using function pointers as const generic parameters is forbidden
   --> $DIR/issue-71381.rs:14:61
diff --git a/tests/ui/const-generics/issues/issue-71611.full.stderr b/tests/ui/const-generics/issues/issue-71611.full.stderr
index 6f6a9fc21a6..e115630b64e 100644
--- a/tests/ui/const-generics/issues/issue-71611.full.stderr
+++ b/tests/ui/const-generics/issues/issue-71611.full.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | fn func<A, const F: fn(inner: A)>(outer: A) {
    |                               ^ the type must not depend on the parameter `A`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/const-generics/issues/issue-71611.min.stderr b/tests/ui/const-generics/issues/issue-71611.min.stderr
index 7252bfd1d6a..b2e2e5cb445 100644
--- a/tests/ui/const-generics/issues/issue-71611.min.stderr
+++ b/tests/ui/const-generics/issues/issue-71611.min.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | fn func<A, const F: fn(inner: A)>(outer: A) {
    |                               ^ the type must not depend on the parameter `A`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error: using function pointers as const generic parameters is forbidden
   --> $DIR/issue-71611.rs:5:21
diff --git a/tests/ui/const-generics/issues/issue-88997.stderr b/tests/ui/const-generics/issues/issue-88997.stderr
index b49d52dd0ba..505ba0da232 100644
--- a/tests/ui/const-generics/issues/issue-88997.stderr
+++ b/tests/ui/const-generics/issues/issue-88997.stderr
@@ -3,16 +3,12 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | struct Range<T: PartialOrd, const MIN: T, const MAX: T>(T)
    |                                        ^ the type must not depend on the parameter `T`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
   --> $DIR/issue-88997.rs:8:54
    |
 LL | struct Range<T: PartialOrd, const MIN: T, const MAX: T>(T)
    |                                                      ^ the type must not depend on the parameter `T`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/const-generics/issues/issue-90364.stderr b/tests/ui/const-generics/issues/issue-90364.stderr
index 6c00a654cde..384ce5da3e2 100644
--- a/tests/ui/const-generics/issues/issue-90364.stderr
+++ b/tests/ui/const-generics/issues/issue-90364.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | pub struct Foo<T, const H: T>(T)
    |                            ^ the type must not depend on the parameter `T`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/error-codes/E0771.stderr b/tests/ui/error-codes/E0771.stderr
index 5e829e6f6d2..dfeaa347941 100644
--- a/tests/ui/error-codes/E0771.stderr
+++ b/tests/ui/error-codes/E0771.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | fn function_with_str<'a, const STRING: &'a str>() {}
    |                                         ^^ the type must not depend on the parameter `'a`
-   |
-   = note: lifetime parameters may not be used in the type of const parameters
 
 warning: the feature `unsized_const_params` is incomplete and may not be safe to use and/or cause compiler crashes
   --> $DIR/E0771.rs:1:30
diff --git a/tests/ui/feature-gates/feature-gate-generic-const-parameter-types.normal.stderr b/tests/ui/feature-gates/feature-gate-generic-const-parameter-types.normal.stderr
new file mode 100644
index 00000000000..1377f845d16
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-generic-const-parameter-types.normal.stderr
@@ -0,0 +1,21 @@
+error[E0770]: the type of const parameters must not depend on other generic parameters
+  --> $DIR/feature-gate-generic-const-parameter-types.rs:7:50
+   |
+LL | struct MyADT<const LEN: usize, const ARRAY: [u8; LEN]>;
+   |                                                  ^^^ the type must not depend on the parameter `LEN`
+
+error: `[u8; LEN]` is forbidden as the type of a const generic parameter
+  --> $DIR/feature-gate-generic-const-parameter-types.rs:7:45
+   |
+LL | struct MyADT<const LEN: usize, const ARRAY: [u8; LEN]>;
+   |                                             ^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool`, and `char`
+help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
+   |
+LL + #![feature(adt_const_params)]
+   |
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0770`.
diff --git a/tests/ui/feature-gates/feature-gate-generic-const-parameter-types.rs b/tests/ui/feature-gates/feature-gate-generic-const-parameter-types.rs
new file mode 100644
index 00000000000..cc374ea3eb2
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-generic-const-parameter-types.rs
@@ -0,0 +1,11 @@
+//@ [feature] check-pass
+//@ revisions: normal feature
+
+#![cfg_attr(feature, feature(adt_const_params, generic_const_parameter_types))]
+#![cfg_attr(feature, expect(incomplete_features))]
+
+struct MyADT<const LEN: usize, const ARRAY: [u8; LEN]>;
+//[normal]~^ ERROR: the type of const parameters must not depend on other generic parameters
+//[normal]~| ERROR: `[u8; LEN]` is forbidden as the type of a const generic parameter
+
+fn main() {}
diff --git a/tests/ui/generic-const-items/wfcheck_err_leak_issue_118179.stderr b/tests/ui/generic-const-items/wfcheck_err_leak_issue_118179.stderr
index 654004571db..2b28e29421c 100644
--- a/tests/ui/generic-const-items/wfcheck_err_leak_issue_118179.stderr
+++ b/tests/ui/generic-const-items/wfcheck_err_leak_issue_118179.stderr
@@ -3,8 +3,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | struct G<T, const N: Vec<T>>(T);
    |                          ^ the type must not depend on the parameter `T`
-   |
-   = note: type parameters may not be used in the type of const parameters
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/lifetimes/unusual-rib-combinations.stderr b/tests/ui/lifetimes/unusual-rib-combinations.stderr
index b7effdc8d61..7373ca8cf84 100644
--- a/tests/ui/lifetimes/unusual-rib-combinations.stderr
+++ b/tests/ui/lifetimes/unusual-rib-combinations.stderr
@@ -9,8 +9,6 @@ error[E0770]: the type of const parameters must not depend on other generic para
    |
 LL | struct Bar<const N: &'a (dyn for<'a> Foo<'a>)>;
    |                      ^^ the type must not depend on the parameter `'a`
-   |
-   = note: lifetime parameters may not be used in the type of const parameters
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
   --> $DIR/unusual-rib-combinations.rs:11:15
diff --git a/tests/ui/wf/ice-hir-wf-check-anon-const-issue-122989.rs b/tests/ui/wf/ice-hir-wf-check-anon-const-issue-122989.rs
index 997bee1e600..89e4b77b6cd 100644
--- a/tests/ui/wf/ice-hir-wf-check-anon-const-issue-122989.rs
+++ b/tests/ui/wf/ice-hir-wf-check-anon-const-issue-122989.rs
@@ -3,6 +3,7 @@ trait Foo<const N: Bar<2>> {
     //~^ WARN trait objects without an explicit `dyn` are deprecated
     //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
     //~| ERROR cycle detected when computing type of `Foo::N`
+    //~| ERROR cycle detected when computing type of `Foo::N`
     fn func() {}
 }
 
diff --git a/tests/ui/wf/ice-hir-wf-check-anon-const-issue-122989.stderr b/tests/ui/wf/ice-hir-wf-check-anon-const-issue-122989.stderr
index 733b729faf0..a381f2acdce 100644
--- a/tests/ui/wf/ice-hir-wf-check-anon-const-issue-122989.stderr
+++ b/tests/ui/wf/ice-hir-wf-check-anon-const-issue-122989.stderr
@@ -13,7 +13,7 @@ LL | trait Foo<const N: dyn Bar<2>> {
    |                    +++
 
 warning: trait objects without an explicit `dyn` are deprecated
-  --> $DIR/ice-hir-wf-check-anon-const-issue-122989.rs:9:20
+  --> $DIR/ice-hir-wf-check-anon-const-issue-122989.rs:10:20
    |
 LL | trait Bar<const M: Foo<2>> {}
    |                    ^^^^^^
@@ -32,7 +32,7 @@ LL | trait Foo<const N: Bar<2>> {
    |           ^^^^^^^^^^^^^^^
    |
 note: ...which requires computing type of `Bar::M`...
-  --> $DIR/ice-hir-wf-check-anon-const-issue-122989.rs:9:11
+  --> $DIR/ice-hir-wf-check-anon-const-issue-122989.rs:10:11
    |
 LL | trait Bar<const M: Foo<2>> {}
    |           ^^^^^^^^^^^^^^^
@@ -44,6 +44,26 @@ LL | trait Foo<const N: Bar<2>> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
-error: aborting due to 1 previous error; 2 warnings emitted
+error[E0391]: cycle detected when computing type of `Foo::N`
+  --> $DIR/ice-hir-wf-check-anon-const-issue-122989.rs:2:11
+   |
+LL | trait Foo<const N: Bar<2>> {
+   |           ^^^^^^^^^^^^^^^
+   |
+note: ...which requires computing type of `Bar::M`...
+  --> $DIR/ice-hir-wf-check-anon-const-issue-122989.rs:10:11
+   |
+LL | trait Bar<const M: Foo<2>> {}
+   |           ^^^^^^^^^^^^^^^
+   = note: ...which again requires computing type of `Foo::N`, completing the cycle
+note: cycle used when computing explicit predicates of trait `Foo`
+  --> $DIR/ice-hir-wf-check-anon-const-issue-122989.rs:2:1
+   |
+LL | trait Foo<const N: Bar<2>> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 2 previous errors; 2 warnings emitted
 
 For more information about this error, try `rustc --explain E0391`.