Rollup merge of rust-lang#126552 - fee1-dead-contrib:rmfx, r=compiler-errors

Remove use of const traits (and `feature(effects)`) from stdlib

The current uses are already unsound because they are using non-const impls in const contexts. We can reintroduce them by reverting the commit in this PR, after rust-lang#120639 lands.

Also, make `effects` an incomplete feature.

cc `@rust-lang/project-const-traits`
r? `@compiler-errors`

Author: matthiaskrgr

alloc/src/lib.rs

@@ -175,7 +175,6 @@
 #![feature(const_mut_refs)]
 #![feature(const_precise_live_drops)]
 #![feature(const_ptr_write)]
-#![feature(const_trait_impl)]
 #![feature(const_try)]
 #![feature(decl_macro)]
 #![feature(dropck_eyepatch)]

core/src/cmp.rs

@@ -245,7 +245,6 @@ use self::Ordering::*;
     append_const_msg
 )]
 #[rustc_diagnostic_item = "PartialEq"]
-#[const_trait]
 pub trait PartialEq<Rhs: ?Sized = Self> {
     /// This method tests for `self` and `other` values to be equal, and is used
     /// by `==`.
@@ -1475,8 +1474,7 @@ mod impls {
     macro_rules! partial_eq_impl {
         ($($t:ty)*) => ($(
             #[stable(feature = "rust1", since = "1.0.0")]
-            #[rustc_const_unstable(feature = "const_cmp", issue = "92391")]
-            impl const PartialEq for $t {
+            impl PartialEq for $t {
                 #[inline]
                 fn eq(&self, other: &$t) -> bool { (*self) == (*other) }
                 #[inline]

core/src/escape.rs

@@ -60,7 +60,7 @@ const fn escape_ascii<const N: usize>(byte: u8) -> ([ascii::Char; N], Range<u8>)
 const fn escape_unicode<const N: usize>(c: char) -> ([ascii::Char; N], Range<u8>) {
     const { assert!(N >= 10 && N < u8::MAX as usize) };
 
-    let c = u32::from(c);
+    let c = c as u32;
 
     // OR-ing `1` ensures that for `c == 0` the code computes that
     // one digit should be printed.

core/src/ffi/c_str.rs

@@ -515,7 +515,10 @@ impl CStr {
     #[inline]
     #[must_use]
     const fn as_non_null_ptr(&self) -> NonNull<c_char> {
-        NonNull::from(&self.inner).as_non_null_ptr()
+        // FIXME(effects) replace with `NonNull::from`
+        // SAFETY: a reference is never null
+        unsafe { NonNull::new_unchecked(&self.inner as *const [c_char] as *mut [c_char]) }
+            .as_non_null_ptr()
     }
 
     /// Returns the length of `self`. Like C's `strlen`, this does not include the nul terminator.

core/src/lib.rs

@@ -200,6 +200,7 @@
 // Language features:
 // tidy-alphabetical-start
 #![cfg_attr(bootstrap, feature(c_unwind))]
+#![cfg_attr(bootstrap, feature(effects))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
 #![feature(allow_internal_unsafe)]
@@ -214,13 +215,11 @@
 #![feature(const_mut_refs)]
 #![feature(const_precise_live_drops)]
 #![feature(const_refs_to_cell)]
-#![feature(const_trait_impl)]
 #![feature(decl_macro)]
 #![feature(deprecated_suggestion)]
 #![feature(doc_cfg)]
 #![feature(doc_cfg_hide)]
 #![feature(doc_notable_trait)]
-#![feature(effects)]
 #![feature(extern_types)]
 #![feature(f128)]
 #![feature(f16)]

core/src/marker.rs

@@ -944,7 +944,6 @@ marker_impls! {
 #[lang = "destruct"]
 #[rustc_on_unimplemented(message = "can't drop `{Self}`", append_const_msg)]
 #[rustc_deny_explicit_impl(implement_via_object = false)]
-#[const_trait]
 pub trait Destruct {}
 
 /// A marker for tuple types.

core/src/num/nonzero.rs

@@ -33,7 +33,6 @@ use super::{IntErrorKind, ParseIntError};
     reason = "implementation detail which may disappear or be replaced at any time",
     issue = "none"
 )]
-#[const_trait]
 pub unsafe trait ZeroablePrimitive: Sized + Copy + private::Sealed {
     #[doc(hidden)]
     type NonZeroInner: Sized + Copy;
@@ -47,7 +46,6 @@ macro_rules! impl_zeroable_primitive {
                 reason = "implementation detail which may disappear or be replaced at any time",
                 issue = "none"
             )]
-            #[const_trait]
             pub trait Sealed {}
 
             $(
@@ -70,14 +68,14 @@ macro_rules! impl_zeroable_primitive {
                 reason = "implementation detail which may disappear or be replaced at any time",
                 issue = "none"
             )]
-            impl const private::Sealed for $primitive {}
+            impl private::Sealed for $primitive {}
 
             #[unstable(
                 feature = "nonzero_internals",
                 reason = "implementation detail which may disappear or be replaced at any time",
                 issue = "none"
             )]
-            unsafe impl const ZeroablePrimitive for $primitive {
+            unsafe impl ZeroablePrimitive for $primitive {
                 type NonZeroInner = private::$NonZeroInner;
             }
         )+

core/src/ops/arith.rs

@@ -73,7 +73,6 @@
     append_const_msg
 )]
 #[doc(alias = "+")]
-#[const_trait]
 pub trait Add<Rhs = Self> {
     /// The resulting type after applying the `+` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -95,8 +94,7 @@ pub trait Add<Rhs = Self> {
 macro_rules! add_impl {
     ($($t:ty)*) => ($(
         #[stable(feature = "rust1", since = "1.0.0")]
-        #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
-        impl const Add for $t {
+        impl Add for $t {
             type Output = $t;
 
             #[inline]

core/src/task/wake.rs

@@ -282,7 +282,7 @@ impl<'a> Context<'a> {
     pub const fn ext(&mut self) -> &mut dyn Any {
         // FIXME: this field makes Context extra-weird about unwind safety
         // can we justify AssertUnwindSafe if we stabilize this? do we care?
-        match &mut *self.ext {
+        match &mut self.ext.0 {
             ExtData::Some(data) => *data,
             ExtData::None(unit) => unit,
         }
@@ -356,7 +356,7 @@ impl<'a> ContextBuilder<'a> {
     #[rustc_const_unstable(feature = "const_waker", issue = "102012")]
     #[unstable(feature = "context_ext", issue = "123392")]
     pub const fn from(cx: &'a mut Context<'_>) -> Self {
-        let ext = match &mut *cx.ext {
+        let ext = match &mut cx.ext.0 {
             ExtData::Some(ext) => ExtData::Some(*ext),
             ExtData::None(()) => ExtData::None(()),
         };

std/src/lib.rs

@@ -284,7 +284,6 @@
 #![feature(cfi_encoding)]
 #![feature(concat_idents)]
 #![feature(const_mut_refs)]
-#![feature(const_trait_impl)]
 #![feature(decl_macro)]
 #![feature(deprecated_suggestion)]
 #![feature(doc_cfg)]