Rollup merge of rust-lang#129759 - dingxiangfei2009:stabilize-const-r…

…efs-to-static, r=petrochenkov

Stabilize `const_refs_to_static`

Close rust-lang#128183
Tracked by rust-lang#119618
cc `@nikomatsakis`

Meanwhile, I am cooking a sub-section in the language reference.

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -355,7 +355,6 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         {
             self.error_emitted = Some(guar);
         }
-        self.check_op_spanned(ops::StaticAccess, span)
     }
 
     fn check_local_or_return_ty(&mut self, ty: Ty<'tcx>, local: Local) {

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -553,33 +553,6 @@ impl<'tcx> NonConstOp<'tcx> for RawPtrToIntCast {
     }
 }
 
-/// An access to a (non-thread-local) `static`.
-#[derive(Debug)]
-pub(crate) struct StaticAccess;
-impl<'tcx> NonConstOp<'tcx> for StaticAccess {
-    fn status_in_item(&self, ccx: &ConstCx<'_, 'tcx>) -> Status {
-        if let hir::ConstContext::Static(_) = ccx.const_kind() {
-            Status::Allowed
-        } else {
-            Status::Unstable(sym::const_refs_to_static)
-        }
-    }
-
-    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
-    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        let mut err = feature_err(
-            &ccx.tcx.sess,
-            sym::const_refs_to_static,
-            span,
-            format!("referencing statics in {}s is unstable", ccx.const_kind(),),
-        );
-        err
-            .note("`static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.")
-            .help("to fix this, the value can be extracted to a `const` and then used.");
-        err
-    }
-}
-
 /// An access to a thread-local `static`.
 #[derive(Debug)]
 pub(crate) struct ThreadLocalAccess;

compiler/rustc_error_codes/src/error_codes/E0013.md

@@ -5,7 +5,7 @@ variable cannot refer to a static variable.
 
 Erroneous code example:
 
-```compile_fail,E0658
+```
 static X: i32 = 42;
 const Y: i32 = X;
 ```

compiler/rustc_feature/src/accepted.rs

@@ -145,6 +145,8 @@ declare_features! (
     (accepted, const_panic, "1.57.0", Some(51999)),
     /// Allows dereferencing raw pointers during const eval.
     (accepted, const_raw_ptr_deref, "1.58.0", Some(51911)),
+    /// Allows creating pointers and references to `static` items in constants.
+    (accepted, const_refs_to_static, "CURRENT_RUSTC_VERSION", Some(119618)),
     /// Allows implementing `Copy` for closures where possible (RFC 2132).
     (accepted, copy_closures, "1.26.0", Some(44490)),
     /// Allows `crate` in paths.

compiler/rustc_feature/src/unstable.rs

@@ -413,8 +413,6 @@ declare_features! (
     (unstable, const_precise_live_drops, "1.46.0", Some(73255)),
     /// Allows references to types with interior mutability within constants
     (unstable, const_refs_to_cell, "1.51.0", Some(80384)),
-    /// Allows creating pointers and references to `static` items in constants.
-    (unstable, const_refs_to_static, "1.78.0", Some(119618)),
     /// Allows `impl const Trait for T` syntax.
     (unstable, const_trait_impl, "1.42.0", Some(67792)),
     /// Allows the `?` operator in const contexts.

tests/ui/asm/const-refs-to-static.rs

@@ -2,8 +2,6 @@
 //@ ignore-nvptx64
 //@ ignore-spirv
 
-#![feature(const_refs_to_static)]
-
 use std::arch::{asm, global_asm};
 use std::ptr::addr_of;
 

tests/ui/asm/const-refs-to-static.stderr

@@ -1,5 +1,5 @@
 error: invalid type for `const` operand
-  --> $DIR/const-refs-to-static.rs:12:19
+  --> $DIR/const-refs-to-static.rs:10:19
    |
 LL | global_asm!("{}", const addr_of!(FOO));
    |                   ^^^^^^-------------
@@ -9,7 +9,7 @@ LL | global_asm!("{}", const addr_of!(FOO));
    = help: `const` operands must be of an integer type
 
 error: invalid type for `const` operand
-  --> $DIR/const-refs-to-static.rs:17:25
+  --> $DIR/const-refs-to-static.rs:15:25
    |
 LL |     unsafe { asm!("{}", const addr_of!(FOO)) };
    |                         ^^^^^^-------------

tests/ui/asm/x86_64/type-check-4.rs

@@ -1,14 +1,12 @@
 //@ only-x86_64
 //@ compile-flags: -C target-feature=+avx512f
-
-use std::arch::{asm, global_asm};
+//@ check-pass
 
 use std::arch::x86_64::{_mm256_setzero_ps, _mm_setzero_ps};
+use std::arch::{asm, global_asm};
 
 fn main() {}
 
-// Constants must be... constant
-
 static S: i32 = 1;
 const fn const_foo(x: i32) -> i32 {
     x
@@ -17,10 +15,7 @@ const fn const_bar<T>(x: T) -> T {
     x
 }
 global_asm!("{}", const S);
-//~^ ERROR referencing statics
 global_asm!("{}", const const_foo(0));
 global_asm!("{}", const const_foo(S));
-//~^ ERROR referencing statics
 global_asm!("{}", const const_bar(0));
 global_asm!("{}", const const_bar(S));
-//~^ ERROR referencing statics

tests/ui/asm/x86_64/type-check-4.stderr

@@ -1,39 +1,6 @@
-error[E0658]: referencing statics in constants is unstable
-  --> $DIR/type-check-4.rs:19:25
+warning: unstable feature specified for `-Ctarget-feature`: `avx512f`
    |
-LL | global_asm!("{}", const S);
-   |                         ^
-   |
-   = note: see issue #119618 <https://github.com/rust-lang/rust/issues/119618> for more information
-   = help: add `#![feature(const_refs_to_static)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-   = note: `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
-   = help: to fix this, the value can be extracted to a `const` and then used.
-
-error[E0658]: referencing statics in constants is unstable
-  --> $DIR/type-check-4.rs:22:35
-   |
-LL | global_asm!("{}", const const_foo(S));
-   |                                   ^
-   |
-   = note: see issue #119618 <https://github.com/rust-lang/rust/issues/119618> for more information
-   = help: add `#![feature(const_refs_to_static)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-   = note: `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
-   = help: to fix this, the value can be extracted to a `const` and then used.
-
-error[E0658]: referencing statics in constants is unstable
-  --> $DIR/type-check-4.rs:25:35
-   |
-LL | global_asm!("{}", const const_bar(S));
-   |                                   ^
-   |
-   = note: see issue #119618 <https://github.com/rust-lang/rust/issues/119618> for more information
-   = help: add `#![feature(const_refs_to_static)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-   = note: `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
-   = help: to fix this, the value can be extracted to a `const` and then used.
+   = note: this feature is not stably supported; its behavior can change in the future
 
-error: aborting due to 3 previous errors
+warning: 1 warning emitted
 
-For more information about this error, try `rustc --explain E0658`.

tests/ui/consts/const-fn-not-safe-for-const.rs

@@ -18,12 +18,10 @@ static Y: u32 = 0;
 
 const fn get_Y() -> u32 {
     Y
-    //~^ ERROR referencing statics in constant functions
 }
 
 const fn get_Y_addr() -> &'static u32 {
     &Y
-    //~^ ERROR referencing statics in constant functions
 }
 
 const fn get() -> u32 {

tests/ui/consts/const-fn-not-safe-for-const.stderr

@@ -6,31 +6,6 @@ LL |     random()
    |
    = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
-error[E0658]: referencing statics in constant functions is unstable
-  --> $DIR/const-fn-not-safe-for-const.rs:20:5
-   |
-LL |     Y
-   |     ^
-   |
-   = note: see issue #119618 <https://github.com/rust-lang/rust/issues/119618> for more information
-   = help: add `#![feature(const_refs_to_static)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-   = note: `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
-   = help: to fix this, the value can be extracted to a `const` and then used.
-
-error[E0658]: referencing statics in constant functions is unstable
-  --> $DIR/const-fn-not-safe-for-const.rs:25:6
-   |
-LL |     &Y
-   |      ^
-   |
-   = note: see issue #119618 <https://github.com/rust-lang/rust/issues/119618> for more information
-   = help: add `#![feature(const_refs_to_static)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-   = note: `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
-   = help: to fix this, the value can be extracted to a `const` and then used.
-
-error: aborting due to 3 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0015, E0658.
-For more information about an error, try `rustc --explain E0015`.
+For more information about this error, try `rustc --explain E0015`.

tests/ui/consts/const-mut-refs/mut_ref_in_final_dynamic_check.rs

@@ -1,7 +1,7 @@
 //@ normalize-stderr-test: "(the raw bytes of the constant) \(size: [0-9]*, align: [0-9]*\)" -> "$1 (size: $$SIZE, align: $$ALIGN)"
 //@ normalize-stderr-test: "( 0x[0-9a-f][0-9a-f] │)? ([0-9a-f][0-9a-f] |__ |╾─*ALLOC[0-9]+(\+[a-z0-9]+)?(<imm>)?─*╼ )+ *│.*" -> " HEX_DUMP"
 //@ normalize-stderr-test: "HEX_DUMP\s*\n\s*HEX_DUMP" -> "HEX_DUMP"
-#![feature(const_mut_refs, const_refs_to_static)]
+#![feature(const_mut_refs)]
 
 use std::sync::Mutex;
 

tests/ui/consts/const-ref-to-static-linux-vtable.rs

@@ -1,6 +1,6 @@
-//@check-pass
+//@ check-pass
 //! This is the reduced version of the "Linux kernel vtable" use-case.
-#![feature(const_mut_refs, const_refs_to_static)]
+#![feature(const_mut_refs)]
 use std::ptr::addr_of_mut;
 
 #[repr(C)]

tests/ui/consts/const_refs_to_static-ice-121413.rs

@@ -3,7 +3,6 @@
 // issue: rust-lang/rust#121413
 //@ compile-flags: -Zextra-const-ub-checks
 // ignore-tidy-linelength
-#![feature(const_refs_to_static)]
 const REF_INTERIOR_MUT: &usize = {
     //~^ HELP consider importing this struct
     static FOO: Sync = AtomicUsize::new(0);

tests/ui/consts/const_refs_to_static-ice-121413.stderr

@@ -1,5 +1,5 @@
 error[E0433]: failed to resolve: use of undeclared type `AtomicUsize`
-  --> $DIR/const_refs_to_static-ice-121413.rs:9:24
+  --> $DIR/const_refs_to_static-ice-121413.rs:8:24
    |
 LL |     static FOO: Sync = AtomicUsize::new(0);
    |                        ^^^^^^^^^^^ use of undeclared type `AtomicUsize`
@@ -10,7 +10,7 @@ LL + use std::sync::atomic::AtomicUsize;
    |
 
 warning: trait objects without an explicit `dyn` are deprecated
-  --> $DIR/const_refs_to_static-ice-121413.rs:9:17
+  --> $DIR/const_refs_to_static-ice-121413.rs:8:17
    |
 LL |     static FOO: Sync = AtomicUsize::new(0);
    |                 ^^^^
@@ -24,15 +24,15 @@ LL |     static FOO: dyn Sync = AtomicUsize::new(0);
    |                 +++
 
 error[E0277]: the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
-  --> $DIR/const_refs_to_static-ice-121413.rs:9:17
+  --> $DIR/const_refs_to_static-ice-121413.rs:8:17
    |
 LL |     static FOO: Sync = AtomicUsize::new(0);
    |                 ^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `(dyn Sync + 'static)`
 
 error[E0277]: the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
-  --> $DIR/const_refs_to_static-ice-121413.rs:9:24
+  --> $DIR/const_refs_to_static-ice-121413.rs:8:24
    |
 LL |     static FOO: Sync = AtomicUsize::new(0);
    |                        ^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time

tests/ui/consts/const_refs_to_static.rs

@@ -1,5 +1,4 @@
 //@ run-pass
-#![feature(const_refs_to_static)]
 
 static S: i32 = 0;
 static mut S_MUT: i32 = 0;

tests/ui/consts/const_refs_to_static_fail.rs

@@ -1,6 +1,6 @@
 //@ normalize-stderr-test: "(the raw bytes of the constant) \(size: [0-9]*, align: [0-9]*\)" -> "$1 (size: $$SIZE, align: $$ALIGN)"
 //@ normalize-stderr-test: "([0-9a-f][0-9a-f] |╾─*ALLOC[0-9]+(\+[a-z0-9]+)?(<imm>)?─*╼ )+ *│.*" -> "HEX_DUMP"
-#![feature(const_refs_to_static, const_mut_refs, sync_unsafe_cell)]
+#![feature(const_mut_refs, sync_unsafe_cell)]
 use std::cell::SyncUnsafeCell;
 
 static S: SyncUnsafeCell<i32> = SyncUnsafeCell::new(0);

tests/ui/consts/const_refs_to_static_fail_invalid.rs

@@ -1,6 +1,5 @@
 //@ normalize-stderr-test: "(the raw bytes of the constant) \(size: [0-9]*, align: [0-9]*\)" -> "$1 (size: $$SIZE, align: $$ALIGN)"
 //@ normalize-stderr-test: "([0-9a-f][0-9a-f] |╾─*ALLOC[0-9]+(\+[a-z0-9]+)?(<imm>)?─*╼ )+ *│.*" -> "HEX_DUMP"
-#![feature(const_refs_to_static)]
 #![allow(static_mut_refs)]
 
 fn invalid() {

tests/ui/consts/const_refs_to_static_fail_invalid.stderr

@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/const_refs_to_static_fail_invalid.rs:9:5
+  --> $DIR/const_refs_to_static_fail_invalid.rs:8:5
    |
 LL |     const C: &bool = unsafe { std::mem::transmute(&S) };
    |     ^^^^^^^^^^^^^^ constructing invalid value at .<deref>: encountered 0x0a, but expected a boolean
@@ -10,7 +10,7 @@ LL |     const C: &bool = unsafe { std::mem::transmute(&S) };
            }
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/const_refs_to_static_fail_invalid.rs:25:5
+  --> $DIR/const_refs_to_static_fail_invalid.rs:24:5
    |
 LL |     const C: &i8 = unsafe { &S };
    |     ^^^^^^^^^^^^ constructing invalid value: encountered reference to `extern` static in `const`
@@ -21,7 +21,7 @@ LL |     const C: &i8 = unsafe { &S };
            }
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/const_refs_to_static_fail_invalid.rs:39:5
+  --> $DIR/const_refs_to_static_fail_invalid.rs:38:5
    |
 LL |     const C: &i32 = unsafe { &S_MUT };
    |     ^^^^^^^^^^^^^ constructing invalid value: encountered reference to mutable memory in `const`
@@ -32,19 +32,19 @@ LL |     const C: &i32 = unsafe { &S_MUT };
            }
 
 error: could not evaluate constant pattern
-  --> $DIR/const_refs_to_static_fail_invalid.rs:15:9
+  --> $DIR/const_refs_to_static_fail_invalid.rs:14:9
    |
 LL |         C => {}
    |         ^
 
 error: could not evaluate constant pattern
-  --> $DIR/const_refs_to_static_fail_invalid.rs:31:9
+  --> $DIR/const_refs_to_static_fail_invalid.rs:30:9
    |
 LL |         C => {}
    |         ^
 
 error: could not evaluate constant pattern
-  --> $DIR/const_refs_to_static_fail_invalid.rs:46:9
+  --> $DIR/const_refs_to_static_fail_invalid.rs:45:9
    |
 LL |         C => {}
    |         ^

tests/ui/consts/issue-17718-const-bad-values.rs

@@ -5,7 +5,6 @@ const C1: &'static mut [usize] = &mut [];
 
 static mut S: usize = 3;
 const C2: &'static mut usize = unsafe { &mut S };
-//~^ ERROR: referencing statics in constants
-//~| ERROR: mutable references are not allowed
+//~^ ERROR: mutable references are not allowed in constants
 
 fn main() {}

tests/ui/consts/issue-17718-const-bad-values.stderr

@@ -4,18 +4,6 @@ error[E0764]: mutable references are not allowed in the final value of constants
 LL | const C1: &'static mut [usize] = &mut [];
    |                                  ^^^^^^^
 
-error[E0658]: referencing statics in constants is unstable
-  --> $DIR/issue-17718-const-bad-values.rs:7:46
-   |
-LL | const C2: &'static mut usize = unsafe { &mut S };
-   |                                              ^
-   |
-   = note: see issue #119618 <https://github.com/rust-lang/rust/issues/119618> for more information
-   = help: add `#![feature(const_refs_to_static)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-   = note: `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
-   = help: to fix this, the value can be extracted to a `const` and then used.
-
 error[E0658]: mutable references are not allowed in constants
   --> $DIR/issue-17718-const-bad-values.rs:7:41
    |
@@ -26,7 +14,7 @@ LL | const C2: &'static mut usize = unsafe { &mut S };
    = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 Some errors have detailed explanations: E0658, E0764.
 For more information about an error, try `rustc --explain E0658`.