Rollup merge of #77420 - ecstatic-morse:const-checking-raw-mut-ref, r=davidtwco

Unify const-checking structured errors for `&mut` and `&raw mut`

Resolves #77414 as well as a FIXME.

Author: JohnTitor

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

@@ -224,7 +224,8 @@ impl NonConstOp for CellBorrow {
 }
 
 #[derive(Debug)]
-pub struct MutBorrow;
+pub struct MutBorrow(pub hir::BorrowKind);
+
 impl NonConstOp for MutBorrow {
     fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status {
         // Forbid everywhere except in const fn with a feature gate
@@ -236,22 +237,28 @@ impl NonConstOp for MutBorrow {
     }
 
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
+        let raw = match self.0 {
+            hir::BorrowKind::Raw => "raw ",
+            hir::BorrowKind::Ref => "",
+        };
+
         let mut err = if ccx.const_kind() == hir::ConstContext::ConstFn {
             feature_err(
                 &ccx.tcx.sess.parse_sess,
                 sym::const_mut_refs,
                 span,
-                &format!("mutable references are not allowed in {}s", ccx.const_kind()),
+                &format!("{}mutable references are not allowed in {}s", raw, ccx.const_kind()),
             )
         } else {
             let mut err = struct_span_err!(
                 ccx.tcx.sess,
                 span,
                 E0764,
-                "mutable references are not allowed in {}s",
+                "{}mutable references are not allowed in {}s",
+                raw,
                 ccx.const_kind(),
             );
-            err.span_label(span, format!("`&mut` is only allowed in `const fn`"));
+            err.span_label(span, format!("`&{}mut` is only allowed in `const fn`", raw));
             err
         };
         if ccx.tcx.sess.teach(&err.get_code().unwrap()) {
@@ -270,29 +277,6 @@ impl NonConstOp for MutBorrow {
     }
 }
 
-// FIXME(ecstaticmorse): Unify this with `MutBorrow`. It has basically the same issues.
-#[derive(Debug)]
-pub struct MutAddressOf;
-impl NonConstOp for MutAddressOf {
-    fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status {
-        // Forbid everywhere except in const fn with a feature gate
-        if ccx.const_kind() == hir::ConstContext::ConstFn {
-            Status::Unstable(sym::const_mut_refs)
-        } else {
-            Status::Forbidden
-        }
-    }
-
-    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
-        feature_err(
-            &ccx.tcx.sess.parse_sess,
-            sym::const_mut_refs,
-            span,
-            &format!("`&raw mut` is not allowed in {}s", ccx.const_kind()),
-        )
-    }
-}
-
 #[derive(Debug)]
 pub struct MutDeref;
 impl NonConstOp for MutDeref {

compiler/rustc_mir/src/transform/check_consts/validation.rs

@@ -525,14 +525,16 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
 
                 if !is_allowed {
                     if let BorrowKind::Mut { .. } = kind {
-                        self.check_op(ops::MutBorrow);
+                        self.check_op(ops::MutBorrow(hir::BorrowKind::Ref));
                     } else {
                         self.check_op(ops::CellBorrow);
                     }
                 }
             }
 
-            Rvalue::AddressOf(Mutability::Mut, _) => self.check_op(ops::MutAddressOf),
+            Rvalue::AddressOf(Mutability::Mut, _) => {
+                self.check_op(ops::MutBorrow(hir::BorrowKind::Raw))
+            }
 
             Rvalue::Ref(_, BorrowKind::Shared | BorrowKind::Shallow, ref place)
             | Rvalue::AddressOf(Mutability::Not, ref place) => {

src/test/ui/consts/const-address-of-mut.rs

@@ -1,14 +1,14 @@
 #![feature(raw_ref_op)]
 
-const A: () = { let mut x = 2; &raw mut x; };           //~ ERROR `&raw mut` is not allowed
+const A: () = { let mut x = 2; &raw mut x; };           //~ mutable reference
 
-static B: () = { let mut x = 2; &raw mut x; };          //~ ERROR `&raw mut` is not allowed
+static B: () = { let mut x = 2; &raw mut x; };          //~ mutable reference
 
-static mut C: () = { let mut x = 2; &raw mut x; };      //~ ERROR `&raw mut` is not allowed
+static mut C: () = { let mut x = 2; &raw mut x; };      //~ mutable reference
 
 const fn foo() {
     let mut x = 0;
-    let y = &raw mut x;                                 //~ ERROR `&raw mut` is not allowed
+    let y = &raw mut x;                                 //~ mutable reference
 }
 
 fn main() {}

src/test/ui/consts/const-address-of-mut.stderr

@@ -1,31 +1,22 @@
-error[E0658]: `&raw mut` is not allowed in constants
+error[E0764]: raw mutable references are not allowed in constants
   --> $DIR/const-address-of-mut.rs:3:32
    |
 LL | const A: () = { let mut x = 2; &raw mut x; };
-   |                                ^^^^^^^^^^
-   |
-   = note: see issue #57349 <https://github.com/rust-lang/rust/issues/57349> for more information
-   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
+   |                                ^^^^^^^^^^ `&raw mut` is only allowed in `const fn`
 
-error[E0658]: `&raw mut` is not allowed in statics
+error[E0764]: raw mutable references are not allowed in statics
   --> $DIR/const-address-of-mut.rs:5:33
    |
 LL | static B: () = { let mut x = 2; &raw mut x; };
-   |                                 ^^^^^^^^^^
-   |
-   = note: see issue #57349 <https://github.com/rust-lang/rust/issues/57349> for more information
-   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
+   |                                 ^^^^^^^^^^ `&raw mut` is only allowed in `const fn`
 
-error[E0658]: `&raw mut` is not allowed in statics
+error[E0764]: raw mutable references are not allowed in statics
   --> $DIR/const-address-of-mut.rs:7:37
    |
 LL | static mut C: () = { let mut x = 2; &raw mut x; };
-   |                                     ^^^^^^^^^^
-   |
-   = note: see issue #57349 <https://github.com/rust-lang/rust/issues/57349> for more information
-   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
+   |                                     ^^^^^^^^^^ `&raw mut` is only allowed in `const fn`
 
-error[E0658]: `&raw mut` is not allowed in constant functions
+error[E0658]: raw mutable references are not allowed in constant functions
   --> $DIR/const-address-of-mut.rs:11:13
    |
 LL |     let y = &raw mut x;
@@ -36,4 +27,5 @@ LL |     let y = &raw mut x;
 
 error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
+Some errors have detailed explanations: E0658, E0764.
+For more information about an error, try `rustc --explain E0658`.

src/test/ui/consts/min_const_fn/address_of.rs

@@ -2,15 +2,15 @@
 
 const fn mutable_address_of_in_const() {
     let mut a = 0;
-    let b = &raw mut a;         //~ ERROR `&raw mut` is not allowed
+    let b = &raw mut a;         //~ ERROR mutable reference
 }
 
 struct X;
 
 impl X {
     const fn inherent_mutable_address_of_in_const() {
         let mut a = 0;
-        let b = &raw mut a;     //~ ERROR `&raw mut` is not allowed
+        let b = &raw mut a;     //~ ERROR mutable reference
     }
 }
 

src/test/ui/consts/min_const_fn/address_of.stderr

@@ -1,4 +1,4 @@
-error[E0658]: `&raw mut` is not allowed in constant functions
+error[E0658]: raw mutable references are not allowed in constant functions
   --> $DIR/address_of.rs:5:13
    |
 LL |     let b = &raw mut a;
@@ -7,7 +7,7 @@ LL |     let b = &raw mut a;
    = note: see issue #57349 <https://github.com/rust-lang/rust/issues/57349> for more information
    = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
 
-error[E0658]: `&raw mut` is not allowed in constant functions
+error[E0658]: raw mutable references are not allowed in constant functions
   --> $DIR/address_of.rs:13:17
    |
 LL |         let b = &raw mut a;