Rollup merge of rust-lang#145095 - tiif:unstable_const_param, r=BoxyUwU

Migrate `UnsizedConstParamTy`  to unstable impl of `ConstParamTy_`

Now that we have ``#[unstable_feature_bound]``, we can remove ``UnsizedConstParamTy`` that was meant to be an unstable impl of stable type and ``ConstParamTy_`` trait.

r? `@BoxyUwU`

Author: Zalathar

core/src/marker.rs

@@ -1083,7 +1083,7 @@ pub trait Tuple {}
 // We name this differently than the derive macro so that the `adt_const_params` can
 // be used independently of `unsized_const_params` without requiring a full path
 // to the derive macro every time it is used. This should be renamed on stabilization.
-pub trait ConstParamTy_: UnsizedConstParamTy + StructuralPartialEq + Eq {}
+pub trait ConstParamTy_: StructuralPartialEq + Eq {}
 
 /// Derive macro generating an impl of the trait `ConstParamTy`.
 #[rustc_builtin_macro]
@@ -1093,23 +1093,6 @@ pub macro ConstParamTy($item:item) {
     /* compiler built-in */
 }
 
-#[lang = "unsized_const_param_ty"]
-#[unstable(feature = "unsized_const_params", issue = "95174")]
-#[diagnostic::on_unimplemented(message = "`{Self}` can't be used as a const parameter type")]
-/// A marker for types which can be used as types of `const` generic parameters.
-///
-/// Equivalent to [`ConstParamTy_`] except that this is used by
-/// the `unsized_const_params` to allow for fake unstable impls.
-pub trait UnsizedConstParamTy: StructuralPartialEq + Eq {}
-
-/// Derive macro generating an impl of the trait `ConstParamTy`.
-#[rustc_builtin_macro]
-#[allow_internal_unstable(unsized_const_params)]
-#[unstable(feature = "unsized_const_params", issue = "95174")]
-pub macro UnsizedConstParamTy($item:item) {
-    /* compiler built-in */
-}
-
 // FIXME(adt_const_params): handle `ty::FnDef`/`ty::Closure`
 marker_impls! {
     #[unstable(feature = "adt_const_params", issue = "95174")]
@@ -1124,17 +1107,11 @@ marker_impls! {
 
 marker_impls! {
     #[unstable(feature = "unsized_const_params", issue = "95174")]
-    UnsizedConstParamTy for
-        usize, u8, u16, u32, u64, u128,
-        isize, i8, i16, i32, i64, i128,
-        bool,
-        char,
-        (),
-        {T: UnsizedConstParamTy, const N: usize} [T; N],
-
+    #[unstable_feature_bound(unsized_const_params)]
+    ConstParamTy_ for
         str,
-        {T: UnsizedConstParamTy} [T],
-        {T: UnsizedConstParamTy + ?Sized} &T,
+        {T: ConstParamTy_} [T],
+        {T: ConstParamTy_ + ?Sized} &T,
 }
 
 /// A common trait implemented by all function pointers.

core/src/mem/transmutability.rs

@@ -1,4 +1,4 @@
-use crate::marker::{ConstParamTy_, UnsizedConstParamTy};
+use crate::marker::ConstParamTy_;
 
 /// Marks that `Src` is transmutable into `Self`.
 ///
@@ -83,6 +83,7 @@ use crate::marker::{ConstParamTy_, UnsizedConstParamTy};
 /// Furthermore, stability does not imply portability. For example, the size of
 /// `usize` is stable, but not portable.
 #[unstable(feature = "transmutability", issue = "99571")]
+#[unstable_feature_bound(transmutability)]
 #[lang = "transmute_trait"]
 #[rustc_deny_explicit_impl]
 #[rustc_do_not_implement_via_object]
@@ -288,9 +289,8 @@ pub struct Assume {
 }
 
 #[unstable(feature = "transmutability", issue = "99571")]
+#[unstable_feature_bound(transmutability)]
 impl ConstParamTy_ for Assume {}
-#[unstable(feature = "transmutability", issue = "99571")]
-impl UnsizedConstParamTy for Assume {}
 
 impl Assume {
     /// With this, [`TransmuteFrom`] does not assume you have ensured any safety

core/src/tuple.rs

@@ -1,7 +1,7 @@
 // See core/src/primitive_docs.rs for documentation.
 
 use crate::cmp::Ordering::{self, *};
-use crate::marker::{ConstParamTy_, StructuralPartialEq, UnsizedConstParamTy};
+use crate::marker::{ConstParamTy_, StructuralPartialEq};
 use crate::ops::ControlFlow::{self, Break, Continue};
 
 // Recursive macro for implementing n-ary tuple functions and operations
@@ -47,17 +47,11 @@ macro_rules! tuple_impls {
         maybe_tuple_doc! {
             $($T)+ @
             #[unstable(feature = "adt_const_params", issue = "95174")]
+            #[unstable_feature_bound(unsized_const_params)]
             impl<$($T: ConstParamTy_),+> ConstParamTy_ for ($($T,)+)
             {}
         }
 
-        maybe_tuple_doc! {
-            $($T)+ @
-            #[unstable(feature = "unsized_const_params", issue = "95174")]
-            impl<$($T: UnsizedConstParamTy),+> UnsizedConstParamTy for ($($T,)+)
-            {}
-        }
-
         maybe_tuple_doc! {
             $($T)+ @
             #[unstable(feature = "structural_match", issue = "31434")]