Auto merge of #110393 - fee1-dead-contrib:rm-const-traits, r=oli-obk

Rm const traits in libcore

See [zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/146212-t-compiler.2Fconst-eval/topic/.60const.20Trait.60.20removal.20or.20rework)

* [x] Bless ui tests
* [ ] Re constify some unstable functions with workarounds if they are needed

Author: bors

compiler/rustc_ast/src/lib.rs

@@ -10,7 +10,6 @@
 )]
 #![feature(associated_type_bounds)]
 #![feature(box_patterns)]
-#![feature(const_default_impls)]
 #![feature(const_trait_impl)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]

compiler/rustc_ast/src/ptr.rs

@@ -126,7 +126,8 @@ impl<S: Encoder, T: Encodable<S>> Encodable<S> for P<T> {
 }
 
 impl<T> P<[T]> {
-    pub const fn new() -> P<[T]> {
+    // FIXME(const-hack) make this const again
+    pub fn new() -> P<[T]> {
         P { ptr: Box::default() }
     }
 

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -610,10 +610,11 @@ pub struct RawPtrComparison;
 impl<'tcx> NonConstOp<'tcx> for RawPtrComparison {
     fn build_error(
         &self,
-        _: &ConstCx<'_, 'tcx>,
+        ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        span_bug!(span, "raw ptr comparison should already be caught in the trait system");
+        // FIXME(const_trait_impl): revert to span_bug?
+        ccx.tcx.sess.create_err(errors::RawPtrComparisonErr { span })
     }
 }
 

library/alloc/src/boxed.rs

@@ -576,8 +576,7 @@ impl<T, A: Allocator> Box<T, A> {
     ///
     /// This conversion does not allocate on the heap and happens in place.
     #[unstable(feature = "box_into_boxed_slice", issue = "71582")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
-    pub const fn into_boxed_slice(boxed: Self) -> Box<[T], A> {
+    pub fn into_boxed_slice(boxed: Self) -> Box<[T], A> {
         let (raw, alloc) = Box::into_raw_with_allocator(boxed);
         unsafe { Box::from_raw_in(raw as *mut [T; 1], alloc) }
     }
@@ -809,9 +808,8 @@ impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> {
     /// assert_eq!(*five, 5)
     /// ```
     #[unstable(feature = "new_uninit", issue = "63291")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const unsafe fn assume_init(self) -> Box<T, A> {
+    pub unsafe fn assume_init(self) -> Box<T, A> {
         let (raw, alloc) = Box::into_raw_with_allocator(self);
         unsafe { Box::from_raw_in(raw as *mut T, alloc) }
     }
@@ -844,9 +842,8 @@ impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> {
     /// }
     /// ```
     #[unstable(feature = "new_uninit", issue = "63291")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const fn write(mut boxed: Self, value: T) -> Box<T, A> {
+    pub fn write(mut boxed: Self, value: T) -> Box<T, A> {
         unsafe {
             (*boxed).write(value);
             boxed.assume_init()
@@ -1090,9 +1087,8 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
     ///
     /// [memory layout]: self#memory-layout
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const fn into_raw_with_allocator(b: Self) -> (*mut T, A) {
+    pub fn into_raw_with_allocator(b: Self) -> (*mut T, A) {
         let (leaked, alloc) = Box::into_unique(b);
         (leaked.as_ptr(), alloc)
     }
@@ -1102,10 +1098,9 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
         issue = "none",
         reason = "use `Box::leak(b).into()` or `Unique::from(Box::leak(b))` instead"
     )]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
     #[doc(hidden)]
-    pub const fn into_unique(b: Self) -> (Unique<T>, A) {
+    pub fn into_unique(b: Self) -> (Unique<T>, A) {
         // Box is recognized as a "unique pointer" by Stacked Borrows, but internally it is a
         // raw pointer for the type system. Turning it directly into a raw pointer would not be
         // recognized as "releasing" the unique pointer to permit aliased raw accesses,
@@ -1163,9 +1158,8 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
     /// assert_eq!(*static_ref, [4, 2, 3]);
     /// ```
     #[stable(feature = "box_leak", since = "1.26.0")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const fn leak<'a>(b: Self) -> &'a mut T
+    pub fn leak<'a>(b: Self) -> &'a mut T
     where
         A: 'a,
     {
@@ -1234,8 +1228,7 @@ impl<T: Default> Default for Box<T> {
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
-impl<T> const Default for Box<[T]> {
+impl<T> Default for Box<[T]> {
     #[inline]
     fn default() -> Self {
         let ptr: Unique<[T]> = Unique::<[T; 0]>::dangling();
@@ -1245,8 +1238,7 @@ impl<T> const Default for Box<[T]> {
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "default_box_extra", since = "1.17.0")]
-#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
-impl const Default for Box<str> {
+impl Default for Box<str> {
     #[inline]
     fn default() -> Self {
         // SAFETY: This is the same as `Unique::cast<U>` but with an unsized `U = str`.
@@ -1443,8 +1435,7 @@ impl<T> From<T> for Box<T> {
 }
 
 #[stable(feature = "pin", since = "1.33.0")]
-#[rustc_const_unstable(feature = "const_box", issue = "92521")]
-impl<T: ?Sized, A: Allocator> const From<Box<T, A>> for Pin<Box<T, A>>
+impl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>>
 where
     A: 'static,
 {
@@ -1880,8 +1871,7 @@ impl<T: ?Sized, A: Allocator> fmt::Pointer for Box<T, A> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_box", issue = "92521")]
-impl<T: ?Sized, A: Allocator> const Deref for Box<T, A> {
+impl<T: ?Sized, A: Allocator> Deref for Box<T, A> {
     type Target = T;
 
     fn deref(&self) -> &T {
@@ -1890,8 +1880,7 @@ impl<T: ?Sized, A: Allocator> const Deref for Box<T, A> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_box", issue = "92521")]
-impl<T: ?Sized, A: Allocator> const DerefMut for Box<T, A> {
+impl<T: ?Sized, A: Allocator> DerefMut for Box<T, A> {
     fn deref_mut(&mut self) -> &mut T {
         &mut **self
     }

library/alloc/src/lib.rs

@@ -106,7 +106,6 @@
 #![feature(coerce_unsized)]
 #![feature(const_align_of_val)]
 #![feature(const_box)]
-#![feature(const_convert)]
 #![feature(const_cow_is_borrowed)]
 #![feature(const_eval_select)]
 #![feature(const_maybe_uninit_as_mut_ptr)]
@@ -174,7 +173,6 @@
 #![feature(associated_type_bounds)]
 #![feature(c_unwind)]
 #![feature(cfg_sanitize)]
-#![feature(const_deref)]
 #![feature(const_mut_refs)]
 #![feature(const_precise_live_drops)]
 #![feature(const_ptr_write)]

library/alloc/src/string.rs

@@ -2247,8 +2247,7 @@ impl_eq! { Cow<'a, str>, &'b str }
 impl_eq! { Cow<'a, str>, String }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
-impl const Default for String {
+impl Default for String {
     /// Creates an empty `String`.
     #[inline]
     fn default() -> String {

library/alloc/src/vec/mod.rs

@@ -3022,8 +3022,7 @@ unsafe impl<#[may_dangle] T, A: Allocator> Drop for Vec<T, A> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
-impl<T> const Default for Vec<T> {
+impl<T> Default for Vec<T> {
     /// Creates an empty `Vec<T>`.
     ///
     /// The vector will not allocate until elements are pushed onto it.

library/alloc/tests/boxed.rs

@@ -61,7 +61,7 @@ fn box_deref_lval() {
 
 pub struct ConstAllocator;
 
-unsafe impl const Allocator for ConstAllocator {
+unsafe impl Allocator for ConstAllocator {
     fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
         match layout.size() {
             0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),

library/alloc/tests/const_fns.rs

@@ -1,13 +1,16 @@
 // Test const functions in the library
 
 pub const MY_VEC: Vec<usize> = Vec::new();
-pub const MY_VEC2: Vec<usize> = Default::default();
+
+// FIXME(#110395)
+// pub const MY_VEC2: Vec<usize> = Default::default();
 
 pub const MY_STRING: String = String::new();
-pub const MY_STRING2: String = Default::default();
 
-pub const MY_BOXED_SLICE: Box<[usize]> = Default::default();
-pub const MY_BOXED_STR: Box<str> = Default::default();
+// pub const MY_STRING2: String = Default::default();
+
+// pub const MY_BOXED_SLICE: Box<[usize]> = Default::default();
+// pub const MY_BOXED_STR: Box<str> = Default::default();
 
 use std::collections::{BTreeMap, BTreeSet};
 
@@ -23,11 +26,11 @@ pub const SET_IS_EMPTY: bool = SET.is_empty();
 
 #[test]
 fn test_const() {
-    assert_eq!(MY_VEC, MY_VEC2);
-    assert_eq!(MY_STRING, MY_STRING2);
+    assert_eq!(MY_VEC, /* MY_VEC */ vec![]);
+    assert_eq!(MY_STRING, /* MY_STRING2 */ String::default());
 
-    assert_eq!(MY_VEC, *MY_BOXED_SLICE);
-    assert_eq!(MY_STRING, *MY_BOXED_STR);
+    // assert_eq!(MY_VEC, *MY_BOXED_SLICE);
+    // assert_eq!(MY_STRING, *MY_BOXED_STR);
 
     assert_eq!(MAP_LEN, 0);
     assert_eq!(SET_LEN, 0);

library/alloc/tests/lib.rs

@@ -3,7 +3,6 @@
 #![feature(assert_matches)]
 #![feature(btree_drain_filter)]
 #![feature(cow_is_borrowed)]
-#![feature(const_convert)]
 #![feature(const_cow_is_borrowed)]
 #![feature(const_heap)]
 #![feature(const_mut_refs)]
@@ -33,7 +32,6 @@
 #![feature(slice_partition_dedup)]
 #![feature(string_remove_matches)]
 #![feature(const_btree_len)]
-#![feature(const_default_impls)]
 #![feature(const_trait_impl)]
 #![feature(const_str_from_utf8)]
 #![feature(panic_update_hook)]