Auto merge of rust-lang#129759 - dingxiangfei2009:stabilize-const-refs-to-static, r=RalfJung

Stabilize `const_refs_to_static`

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

Author: bors

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -317,7 +317,6 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         {
             self.error_emitted = Some(guar);
         }
-        self.check_op_spanned(ops::StaticAccess, span)
     }
 
     /// Returns whether this place can possibly escape the evaluation of the current const/static

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -16,7 +16,6 @@ use rustc_middle::ty::{
     suggest_constraining_type_param,
 };
 use rustc_middle::util::{CallDesugaringKind, CallKind, call_kind};
-use rustc_session::parse::feature_err;
 use rustc_span::symbol::sym;
 use rustc_span::{BytePos, Pos, Span, Symbol};
 use rustc_trait_selection::traits::SelectionContext;
@@ -477,33 +476,6 @@ 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

@@ -151,6 +151,8 @@ declare_features! (
     (accepted, const_raw_ptr_deref, "1.58.0", Some(51911)),
     /// Allows references to types with interior mutability within constants
     (accepted, const_refs_to_cell, "CURRENT_RUSTC_VERSION", Some(80384)),
+    /// 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

@@ -407,8 +407,6 @@ declare_features! (
     (unstable, const_for, "1.56.0", Some(87575)),
     /// Be more precise when looking for live drops in a const context.
     (unstable, const_precise_live_drops, "1.46.0", Some(73255)),
-    /// 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.

src/tools/tidy/src/issues.txt

@@ -764,7 +764,6 @@ ui/consts/issue-46553.rs
 ui/consts/issue-47789.rs
 ui/consts/issue-50439.rs
 ui/consts/issue-52023-array-size-pointer-cast.rs
-ui/consts/issue-52060.rs
 ui/consts/issue-54224.rs
 ui/consts/issue-54348.rs
 ui/consts/issue-54387.rs
@@ -3830,7 +3829,6 @@ ui/stability-attribute/issue-28388-3.rs
 ui/stability-attribute/issue-99286-stable-intrinsics.rs
 ui/static/auxiliary/issue_24843.rs
 ui/static/issue-1660.rs
-ui/static/issue-18118-2.rs
 ui/static/issue-18118.rs
 ui/static/issue-24446.rs
 ui/static/issue-24843.rs

tests/ui/asm/aarch64/type-check-4.rs

@@ -1,31 +1,27 @@
 //@ only-aarch64
-//@ compile-flags: -C target-feature=+neon
+//@ build-fail
 
-#![feature(repr_simd)]
-
-use std::arch::aarch64::float64x2_t;
-use std::arch::{asm, global_asm};
-
-#[repr(simd)]
-#[derive(Copy, Clone)]
-struct Simd256bit([f64; 4]);
+use std::arch::global_asm;
 
 fn main() {}
 
 // Constants must be... constant
 
-static S: i32 = 1;
+static mut S: i32 = 1;
 const fn const_foo(x: i32) -> i32 {
     x
 }
 const fn const_bar<T>(x: T) -> T {
     x
 }
-global_asm!("{}", const S);
-//~^ ERROR referencing statics
+global_asm!("{}", const unsafe { S });
+//~^ ERROR: evaluation of constant value failed
+//~| mutable global memory
 global_asm!("{}", const const_foo(0));
-global_asm!("{}", const const_foo(S));
-//~^ ERROR referencing statics
+global_asm!("{}", const const_foo(unsafe { S }));
+//~^ ERROR: evaluation of constant value failed
+//~| mutable global memory
 global_asm!("{}", const const_bar(0));
-global_asm!("{}", const const_bar(S));
-//~^ ERROR referencing statics
+global_asm!("{}", const const_bar(unsafe { S }));
+//~^ ERROR: evaluation of constant value failed
+//~| mutable global memory

tests/ui/asm/aarch64/type-check-4.stderr

@@ -1,39 +1,21 @@
-error[E0658]: referencing statics in constants is unstable
-  --> $DIR/type-check-4.rs:24:25
+error[E0080]: evaluation of constant value failed
+  --> $DIR/type-check-4.rs:17:34
    |
-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.
+LL | global_asm!("{}", const unsafe { S });
+   |                                  ^ constant accesses mutable global memory
 
-error[E0658]: referencing statics in constants is unstable
-  --> $DIR/type-check-4.rs:27:35
-   |
-LL | global_asm!("{}", const const_foo(S));
-   |                                   ^
+error[E0080]: evaluation of constant value failed
+  --> $DIR/type-check-4.rs:21:44
    |
-   = 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.
+LL | global_asm!("{}", const const_foo(unsafe { S }));
+   |                                            ^ constant accesses mutable global memory
 
-error[E0658]: referencing statics in constants is unstable
-  --> $DIR/type-check-4.rs:30:35
-   |
-LL | global_asm!("{}", const const_bar(S));
-   |                                   ^
+error[E0080]: evaluation of constant value failed
+  --> $DIR/type-check-4.rs:25:44
    |
-   = 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.
+LL | global_asm!("{}", const const_bar(unsafe { S }));
+   |                                            ^ constant accesses mutable global memory
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
+For more information about this error, try `rustc --explain E0080`.

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)) };
    |                         ^^^^^^-------------