Rollup merge of #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 #120639 lands.

Also, make `effects` an incomplete feature.

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

Author: matthiaskrgr

compiler/rustc_feature/src/unstable.rs

@@ -449,7 +449,7 @@ declare_features! (
     /// Allows `dyn* Trait` objects.
     (incomplete, dyn_star, "1.65.0", Some(102425)),
     /// Uses generic effect parameters for ~const bounds
-    (unstable, effects, "1.72.0", Some(102090)),
+    (incomplete, effects, "1.72.0", Some(102090)),
     /// Allows exhaustive pattern matching on types that contain uninhabited types.
     (unstable, exhaustive_patterns, "1.13.0", Some(51085)),
     /// Allows explicit tail calls via `become` expression.

compiler/rustc_hir_analysis/src/check/intrinsic.rs

@@ -429,17 +429,17 @@ pub fn check_intrinsic_type(
 
             sym::ptr_guaranteed_cmp => (
                 1,
-                1,
+                0,
                 vec![Ty::new_imm_ptr(tcx, param(0)), Ty::new_imm_ptr(tcx, param(0))],
                 tcx.types.u8,
             ),
 
             sym::const_allocate => {
-                (0, 1, vec![tcx.types.usize, tcx.types.usize], Ty::new_mut_ptr(tcx, tcx.types.u8))
+                (0, 0, vec![tcx.types.usize, tcx.types.usize], Ty::new_mut_ptr(tcx, tcx.types.u8))
             }
             sym::const_deallocate => (
                 0,
-                1,
+                0,
                 vec![Ty::new_mut_ptr(tcx, tcx.types.u8), tcx.types.usize, tcx.types.usize],
                 tcx.types.unit,
             ),
@@ -478,16 +478,16 @@ pub fn check_intrinsic_type(
             | sym::frem_algebraic => (1, 0, vec![param(0), param(0)], param(0)),
             sym::float_to_int_unchecked => (2, 0, vec![param(0)], param(1)),
 
-            sym::assume => (0, 1, vec![tcx.types.bool], tcx.types.unit),
-            sym::likely => (0, 1, vec![tcx.types.bool], tcx.types.bool),
-            sym::unlikely => (0, 1, vec![tcx.types.bool], tcx.types.bool),
+            sym::assume => (0, 0, vec![tcx.types.bool], tcx.types.unit),
+            sym::likely => (0, 0, vec![tcx.types.bool], tcx.types.bool),
+            sym::unlikely => (0, 0, vec![tcx.types.bool], tcx.types.bool),
 
             sym::read_via_copy => (1, 0, vec![Ty::new_imm_ptr(tcx, param(0))], param(0)),
             sym::write_via_move => {
                 (1, 0, vec![Ty::new_mut_ptr(tcx, param(0)), param(0)], tcx.types.unit)
             }
 
-            sym::typed_swap => (1, 1, vec![Ty::new_mut_ptr(tcx, param(0)); 2], tcx.types.unit),
+            sym::typed_swap => (1, 0, vec![Ty::new_mut_ptr(tcx, param(0)); 2], tcx.types.unit),
 
             sym::discriminant_value => {
                 let assoc_items = tcx.associated_item_def_ids(
@@ -566,20 +566,20 @@ pub fn check_intrinsic_type(
 
             sym::black_box => (1, 0, vec![param(0)], param(0)),
 
-            sym::is_val_statically_known => (1, 1, vec![param(0)], tcx.types.bool),
+            sym::is_val_statically_known => (1, 0, vec![param(0)], tcx.types.bool),
 
-            sym::const_eval_select => (4, 1, vec![param(0), param(1), param(2)], param(3)),
+            sym::const_eval_select => (4, 0, vec![param(0), param(1), param(2)], param(3)),
 
             sym::vtable_size | sym::vtable_align => {
                 (0, 0, vec![Ty::new_imm_ptr(tcx, tcx.types.unit)], tcx.types.usize)
             }
 
             // This type check is not particularly useful, but the `where` bounds
             // on the definition in `core` do the heavy lifting for checking it.
-            sym::aggregate_raw_ptr => (3, 1, vec![param(1), param(2)], param(0)),
-            sym::ptr_metadata => (2, 1, vec![Ty::new_imm_ptr(tcx, param(0))], param(1)),
+            sym::aggregate_raw_ptr => (3, 0, vec![param(1), param(2)], param(0)),
+            sym::ptr_metadata => (2, 0, vec![Ty::new_imm_ptr(tcx, param(0))], param(1)),
 
-            sym::ub_checks => (0, 1, Vec::new(), tcx.types.bool),
+            sym::ub_checks => (0, 0, Vec::new(), tcx.types.bool),
 
             sym::simd_eq
             | sym::simd_ne

library/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)]

library/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]

library/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.

library/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.

library/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)]

library/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.

library/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;
             }
         )+

library/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]

library/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(()),
         };

library/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)]

src/doc/unstable-book/src/language-features/intrinsics.md

@@ -18,7 +18,7 @@ All intrinsic fallback bodies are automatically made cross-crate inlineable (lik
 by the codegen backend, but not the MIR inliner.
 
 ```rust
-#![feature(rustc_attrs, effects)]
+#![feature(rustc_attrs)]
 #![allow(internal_features)]
 
 #[rustc_intrinsic]
@@ -28,7 +28,7 @@ const unsafe fn const_deallocate(_ptr: *mut u8, _size: usize, _align: usize) {}
 Since these are just regular functions, it is perfectly ok to create the intrinsic twice:
 
 ```rust
-#![feature(rustc_attrs, effects)]
+#![feature(rustc_attrs)]
 #![allow(internal_features)]
 
 #[rustc_intrinsic]

src/tools/miri/tests/fail/intrinsic_fallback_is_spec.rs

@@ -1,4 +1,4 @@
-#![feature(rustc_attrs, effects)]
+#![feature(rustc_attrs)]
 
 #[rustc_intrinsic]
 #[rustc_nounwind]

tests/crashes/120503.rs

@@ -2,6 +2,7 @@
 
 #![crate_name = "foo"]
 #![feature(effects, const_trait_impl)]
+#![allow(incomplete_features)]
 
 #[const_trait]
 pub trait Tr {

tests/crashes/121536.rs

@@ -1,5 +1,6 @@
 #![crate_name = "foo"]
 #![feature(effects)]
+#![allow(incomplete_features)]
 
 // @has foo/fn.bar.html
 // @has - '//pre[@class="rust item-decl"]' 'pub const fn bar() -> '

tests/rustdoc/const-effect-param.rs

@@ -7,6 +7,7 @@
 // not remove this test.
 //
 // FIXME(effects) add `const_trait` to `Fn` so we use `~const`
+// FIXME(effects) restore `const_trait` to `Destruct`
 #![feature(const_trait_impl)]
 #![crate_name = "foo"]
 
@@ -24,9 +25,9 @@ pub trait Tr<T> {
     // @has - '//section[@id="method.a"]/h4[@class="code-header"]/a[@class="trait"]' 'Fn'
     // @!has - '//section[@id="method.a"]/h4[@class="code-header"]/span[@class="where"]' '~const'
     // @has - '//section[@id="method.a"]/h4[@class="code-header"]/div[@class="where"]' ': Fn'
-    fn a<A: /* ~const */ Fn() + ~const Destruct>()
+    fn a<A: /* ~const */ Fn() /* + ~const Destruct */>()
     where
-        Option<A>: /* ~const */ Fn() + ~const Destruct,
+        Option<A>: /* ~const */ Fn() /* + ~const Destruct */,
     {
     }
 }
@@ -36,13 +37,13 @@ pub trait Tr<T> {
 // @has - '//section[@id="impl-Tr%3CT%3E-for-T"]/h3[@class="code-header"]/a[@class="trait"]' 'Fn'
 // @!has - '//section[@id="impl-Tr%3CT%3E-for-T"]/h3[@class="code-header"]/span[@class="where"]' '~const'
 // @has - '//section[@id="impl-Tr%3CT%3E-for-T"]/h3[@class="code-header"]/div[@class="where"]' ': Fn'
-impl<T: /* ~const */ Fn() + ~const Destruct> const Tr<T> for T
+impl<T: /* ~const */ Fn() /* + ~const Destruct */> const Tr<T> for T
 where
-    Option<T>: /* ~const */ Fn() + ~const Destruct,
+    Option<T>: /* ~const */ Fn() /* + ~const Destruct */,
 {
-    fn a<A: /* ~const */ Fn() + ~const Destruct>()
+    fn a<A: /* ~const */ Fn() /* + ~const Destruct */>()
     where
-        Option<A>: /* ~const */ Fn() + ~const Destruct,
+        Option<A>: /* ~const */ Fn() /* + ~const Destruct */,
     {
     }
 }
@@ -51,9 +52,9 @@ where
 // @has - '//pre[@class="rust item-decl"]/code/a[@class="trait"]' 'Fn'
 // @!has - '//pre[@class="rust item-decl"]/code/div[@class="where"]' '~const'
 // @has - '//pre[@class="rust item-decl"]/code/div[@class="where"]' ': Fn'
-pub const fn foo<F: /* ~const */ Fn() + ~const Destruct>()
+pub const fn foo<F: /* ~const */ Fn() /* + ~const Destruct */>()
 where
-    Option<F>: /* ~const */ Fn() + ~const Destruct,
+    Option<F>: /* ~const */ Fn() /* + ~const Destruct */,
 {
     F::a()
 }
@@ -63,9 +64,9 @@ impl<T> S<T> {
     // @has - '//section[@id="method.foo"]/h4[@class="code-header"]/a[@class="trait"]' 'Fn'
     // @!has - '//section[@id="method.foo"]/h4[@class="code-header"]/span[@class="where"]' '~const'
     // @has - '//section[@id="method.foo"]/h4[@class="code-header"]/div[@class="where"]' ': Fn'
-    pub const fn foo<B, C: /* ~const */ Fn() + ~const Destruct>()
+    pub const fn foo<B, C: /* ~const */ Fn() /* + ~const Destruct */>()
     where
-        B: /* ~const */ Fn() + ~const Destruct,
+        B: /* ~const */ Fn() /* + ~const Destruct */,
     {
         B::a()
     }

tests/rustdoc/const-fn-effects.rs

@@ -1,6 +1,6 @@
 //@ build-pass
 
-#![feature(const_trait_impl, effects)]
+#![feature(const_trait_impl, effects)] //~ WARN the feature `effects` is incomplete
 
 #[const_trait]
 trait Func<T> {

tests/rustdoc/rfc-2632-const-trait-impl.rs

@@ -0,0 +1,11 @@
+warning: the feature `effects` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/const_trait_fn-issue-88433.rs:3:30
+   |
+LL | #![feature(const_trait_impl, effects)]
+   |                              ^^^^^^^
+   |
+   = note: see issue #102090 <https://github.com/rust-lang/rust/issues/102090> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+

tests/ui/const-generics/const_trait_fn-issue-88433.rs

@@ -1,5 +1,5 @@
 #![crate_type = "lib"]
-#![feature(const_closures, const_trait_impl, effects)]
+#![feature(const_closures, const_trait_impl, effects)] //~ WARN the feature `effects` is incomplete
 
 pub const fn test() {
     let cl = const || {};