Revert "Make the Step implementations const."

This reverts commit 7bc67ef.

Author: fee1-dead

library/core/src/iter/range.rs

@@ -21,8 +21,7 @@ unsafe_impl_trusted_step![char i8 i16 i32 i64 i128 isize u8 u16 u32 u64 u128 usi
 /// The *successor* operation moves towards values that compare greater.
 /// The *predecessor* operation moves towards values that compare lesser.
 #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
-#[const_trait]
-pub trait Step: ~const Clone + ~const PartialOrd + Sized {
+pub trait Step: Clone + PartialOrd + Sized {
     /// Returns the number of *successor* steps required to get from `start` to `end`.
     ///
     /// Returns `None` if the number of steps would overflow `usize`
@@ -236,8 +235,7 @@ macro_rules! step_integer_impls {
         $(
             #[allow(unreachable_patterns)]
             #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
-            #[rustc_const_unstable(feature = "const_iter", issue = "92476")]
-            impl const Step for $u_narrower {
+            impl Step for $u_narrower {
                 step_identical_methods!();
 
                 #[inline]
@@ -269,8 +267,7 @@ macro_rules! step_integer_impls {
 
             #[allow(unreachable_patterns)]
             #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
-            #[rustc_const_unstable(feature = "const_iter", issue = "92476")]
-            impl const Step for $i_narrower {
+            impl Step for $i_narrower {
                 step_identical_methods!();
 
                 #[inline]
@@ -334,8 +331,7 @@ macro_rules! step_integer_impls {
         $(
             #[allow(unreachable_patterns)]
             #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
-            #[rustc_const_unstable(feature = "const_iter", issue = "92476")]
-            impl const Step for $u_wider {
+            impl Step for $u_wider {
                 step_identical_methods!();
 
                 #[inline]
@@ -360,8 +356,7 @@ macro_rules! step_integer_impls {
 
             #[allow(unreachable_patterns)]
             #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
-            #[rustc_const_unstable(feature = "const_iter", issue = "92476")]
-            impl const Step for $i_wider {
+            impl Step for $i_wider {
                 step_identical_methods!();
 
                 #[inline]
@@ -411,8 +406,7 @@ step_integer_impls! {
 }
 
 #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
-#[rustc_const_unstable(feature = "const_iter", issue = "92476")]
-impl const Step for char {
+impl Step for char {
     #[inline]
     fn steps_between(&start: &char, &end: &char) -> Option<usize> {
         let start = start as u32;
@@ -430,7 +424,6 @@ impl const Step for char {
     }
 
     #[inline]
-    #[rustc_allow_const_fn_unstable(const_try)]
     fn forward_checked(start: char, count: usize) -> Option<char> {
         let start = start as u32;
         let mut res = Step::forward_checked(start, count)?;
@@ -447,7 +440,6 @@ impl const Step for char {
     }
 
     #[inline]
-    #[rustc_allow_const_fn_unstable(const_try)]
     fn backward_checked(start: char, count: usize) -> Option<char> {
         let start = start as u32;
         let mut res = Step::backward_checked(start, count)?;

library/core/src/iter/traits/marker.rs

@@ -86,5 +86,4 @@ pub unsafe trait InPlaceIterable: Iterator {}
 /// for details. Consumers are free to rely on the invariants in unsafe code.
 #[unstable(feature = "trusted_step", issue = "85731")]
 #[rustc_specialization_trait]
-#[const_trait]
-pub unsafe trait TrustedStep: ~const Step {}
+pub unsafe trait TrustedStep: Step {}

library/core/src/lib.rs

@@ -126,7 +126,6 @@
 #![feature(const_intrinsic_forget)]
 #![feature(const_ipv4)]
 #![feature(const_ipv6)]
-#![feature(const_iter)]
 #![feature(const_likely)]
 #![feature(const_maybe_uninit_uninit_array)]
 #![feature(const_maybe_uninit_as_mut_ptr)]