Remove the const_raw_ptr_comparison feature gate.

We can never supply a meaningful implementation of this.
Instead, the follow up commits will create two intrinsics
that approximate comparisons:

* `ptr_maybe_eq`
* `ptr_maybe_ne`

The fact that `ptr_maybe_eq(a, b)` is not necessarily the same
value as `!ptr_maybe_ne(a, b)` is a symptom of this entire
problem.

27 files changed, 165 insertions, 190 deletions

diff --git a/src/librustc_feature/active.rs b/src/librustc_feature/active.rs
index d186f35a12b..f167ed97f57 100644
--- a/src/librustc_feature/active.rs
+++ b/src/librustc_feature/active.rs
@@ -401,9 +401,6 @@ declare_features! (
     /// Allows dereferencing raw pointers during const eval.
     (active, const_raw_ptr_deref, "1.27.0", Some(51911), None),
 
-    /// Allows comparing raw pointers during const eval.
-    (active, const_compare_raw_pointers, "1.27.0", Some(53020), None),
-
     /// Allows `#[doc(alias = "...")]`.
     (active, doc_alias, "1.27.0", Some(50146), None),
 
diff --git a/src/librustc_feature/removed.rs b/src/librustc_feature/removed.rs
index 4e348054fbd..8d410894e8b 100644
--- a/src/librustc_feature/removed.rs
+++ b/src/librustc_feature/removed.rs
@@ -113,6 +113,11 @@ declare_features! (
      Some("removed in favor of `#![feature(marker_trait_attr)]`")),
     /// Allows `#[no_debug]`.
     (removed, no_debug, "1.43.0", Some(29721), None, Some("removed due to lack of demand")),
+
+    /// Allows comparing raw pointers during const eval.
+    (removed, const_compare_raw_pointers, "1.46.0", Some(53020), None,
+     Some("cannot be allowed in const eval in any meaningful way")),
+
     // -------------------------------------------------------------------------
     // feature-group-end: removed features
     // -------------------------------------------------------------------------
diff --git a/src/librustc_mir/transform/check_consts/ops.rs b/src/librustc_mir/transform/check_consts/ops.rs
index d5059c98c95..f09b598ce06 100644
--- a/src/librustc_mir/transform/check_consts/ops.rs
+++ b/src/librustc_mir/transform/check_consts/ops.rs
@@ -284,18 +284,24 @@ impl NonConstOp for Panic {
 #[derive(Debug)]
 pub struct RawPtrComparison;
 impl NonConstOp for RawPtrComparison {
-    fn feature_gate() -> Option<Symbol> {
-        Some(sym::const_compare_raw_pointers)
-    }
-
     fn emit_error(&self, ccx: &ConstCx<'_, '_>, span: Span) {
-        feature_err(
-            &ccx.tcx.sess.parse_sess,
-            sym::const_compare_raw_pointers,
+        let mut err = ccx.tcx.sess.struct_span_err(
             span,
-            &format!("comparing raw pointers inside {}", ccx.const_kind()),
-        )
-        .emit();
+            "pointers cannot be compared in a meaningful way during const eval.",
+        );
+        err.note(
+            "It is conceptually impossible for const eval to know in all cases whether two \
+             pointers are equal. While sometimes it is clear (the address of a static item \
+             is never equal to the address of another static item), comparing an integer \
+             address with any allocation's address is impossible to do at compile-time.",
+        );
+        err.note(
+            "That said, there's the `ptr_maybe_eq` intrinsic which returns `true` for all \
+             comparisons where CTFE isn't sure whether two addresses are equal. The mirror \
+             intrinsic `ptr_maybe_ne` returns `true` for all comparisons where CTFE isn't \
+             sure whether two addresses are inequal.",
+        );
+        err.emit();
     }
 }
 
diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index 7dbb2ebad8b..ac7acff1eca 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -171,21 +171,6 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
                     _ => {}
                 }
             }
-            // raw pointer and fn pointer operations are unsafe as it is not clear whether one
-            // pointer would be "less" or "equal" to another, because we cannot know where llvm
-            // or the linker will place various statics in memory. Without this information the
-            // result of a comparison of addresses would differ between runtime and compile-time.
-            Rvalue::BinaryOp(_, ref lhs, _)
-                if self.const_context && self.tcx.features().const_compare_raw_pointers =>
-            {
-                if let ty::RawPtr(_) | ty::FnPtr(..) = lhs.ty(self.body, self.tcx).kind {
-                    self.require_unsafe(
-                        "pointer operation",
-                        "operations on pointers in constants",
-                        UnsafetyViolationKind::General,
-                    );
-                }
-            }
             _ => {}
         }
         self.super_rvalue(rvalue, location);
diff --git a/src/librustc_typeck/collect/type_of.rs b/src/librustc_typeck/collect/type_of.rs
index cf5f2ec69d8..3dd9c9c5c39 100644
--- a/src/librustc_typeck/collect/type_of.rs
+++ b/src/librustc_typeck/collect/type_of.rs
@@ -10,8 +10,7 @@ use rustc_middle::hir::map::Map;
 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt, TypeFoldable};
-use rustc_session::parse::feature_err;
-use rustc_span::symbol::{sym, Ident};
+use rustc_span::symbol::Ident;
 use rustc_span::{Span, DUMMY_SP};
 use rustc_trait_selection::traits;
 
@@ -303,25 +302,22 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
             GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
             GenericParamKind::Const { ty: ref hir_ty, .. } => {
                 let ty = icx.to_ty(hir_ty);
-                if !tcx.features().const_compare_raw_pointers {
-                    let err = match ty.peel_refs().kind {
-                        ty::FnPtr(_) => Some("function pointers"),
-                        ty::RawPtr(_) => Some("raw pointers"),
-                        _ => None,
-                    };
-                    if let Some(unsupported_type) = err {
-                        feature_err(
-                            &tcx.sess.parse_sess,
-                            sym::const_compare_raw_pointers,
+                let err = match ty.peel_refs().kind {
+                    ty::FnPtr(_) => Some("function pointers"),
+                    ty::RawPtr(_) => Some("raw pointers"),
+                    _ => None,
+                };
+                if let Some(unsupported_type) = err {
+                    tcx.sess
+                        .struct_span_err(
                             hir_ty.span,
                             &format!(
-                                "using {} as const generic parameters is unstable",
+                                "using {} as const generic parameters is forbidden",
                                 unsupported_type
                             ),
                         )
                         .emit();
-                    };
-                }
+                };
                 if traits::search_for_structural_match_violation(param.hir_id, param.span, tcx, ty)
                     .is_some()
                 {
diff --git a/src/test/ui/const-generics/fn-const-param-call.rs b/src/test/ui/const-generics/fn-const-param-call.rs
index afa577fa67f..90c438b05cb 100644
--- a/src/test/ui/const-generics/fn-const-param-call.rs
+++ b/src/test/ui/const-generics/fn-const-param-call.rs
@@ -1,15 +1,14 @@
-// run-pass
-
-#![feature(const_generics, const_compare_raw_pointers)]
+#![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete
 
 fn function() -> u32 {
     17
 }
 
-struct Wrapper<const F: fn() -> u32>;
+struct Wrapper<const F: fn() -> u32>; //~ ERROR: using function pointers as const generic parameters
 
 impl<const F: fn() -> u32> Wrapper<F> {
+//~^ ERROR: using function pointers as const generic parameters
     fn call() -> u32 {
         F()
     }
diff --git a/src/test/ui/const-generics/fn-const-param-call.stderr b/src/test/ui/const-generics/fn-const-param-call.stderr
index 9c0f7e3ab9b..b5811243caa 100644
--- a/src/test/ui/const-generics/fn-const-param-call.stderr
+++ b/src/test/ui/const-generics/fn-const-param-call.stderr
@@ -1,11 +1,23 @@
 warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/fn-const-param-call.rs:3:12
+  --> $DIR/fn-const-param-call.rs:1:12
    |
-LL | #![feature(const_generics, const_compare_raw_pointers)]
+LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
    |
    = note: `#[warn(incomplete_features)]` on by default
    = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
 
-warning: 1 warning emitted
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/fn-const-param-call.rs:8:25
+   |
+LL | struct Wrapper<const F: fn() -> u32>;
+   |                         ^^^^^^^^^^^
+
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/fn-const-param-call.rs:10:15
+   |
+LL | impl<const F: fn() -> u32> Wrapper<F> {
+   |               ^^^^^^^^^^^
+
+error: aborting due to 2 previous errors; 1 warning emitted
 
diff --git a/src/test/ui/const-generics/fn-const-param-infer.rs b/src/test/ui/const-generics/fn-const-param-infer.rs
index 08f6e0db31c..14fa3b494b3 100644
--- a/src/test/ui/const-generics/fn-const-param-infer.rs
+++ b/src/test/ui/const-generics/fn-const-param-infer.rs
@@ -1,7 +1,8 @@
-#![feature(const_generics, const_compare_raw_pointers)]
+#![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete
 
 struct Checked<const F: fn(usize) -> bool>;
+//~^ ERROR: using function pointers as const generic parameters
 
 fn not_one(val: usize) -> bool { val != 1 }
 fn not_two(val: usize) -> bool { val != 2 }
@@ -13,14 +14,14 @@ fn generic<T>(val: usize) -> bool { val != 1 }
 fn main() {
     let _: Option<Checked<not_one>> = None;
     let _: Checked<not_one> = Checked::<not_one>;
-    let _: Checked<not_one> = Checked::<not_two>; //~ mismatched types
+    let _: Checked<not_one> = Checked::<not_two>;
 
     let _ = Checked::<generic_arg>;
     let _ = Checked::<{generic_arg::<usize>}>;
-    let _ = Checked::<{generic_arg::<u32>}>;  //~ mismatched types
+    let _ = Checked::<{generic_arg::<u32>}>;
 
-    let _ = Checked::<generic>; //~ type annotations needed
+    let _ = Checked::<generic>;
     let _ = Checked::<{generic::<u16>}>;
     let _: Checked<{generic::<u16>}> = Checked::<{generic::<u16>}>;
-    let _: Checked<{generic::<u32>}> = Checked::<{generic::<u16>}>; //~ mismatched types
+    let _: Checked<{generic::<u32>}> = Checked::<{generic::<u16>}>;
 }
diff --git a/src/test/ui/const-generics/fn-const-param-infer.stderr b/src/test/ui/const-generics/fn-const-param-infer.stderr
index de41d2984a6..7aaa41eb7d7 100644
--- a/src/test/ui/const-generics/fn-const-param-infer.stderr
+++ b/src/test/ui/const-generics/fn-const-param-infer.stderr
@@ -1,46 +1,17 @@
 warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
   --> $DIR/fn-const-param-infer.rs:1:12
    |
-LL | #![feature(const_generics, const_compare_raw_pointers)]
+LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
    |
    = note: `#[warn(incomplete_features)]` on by default
    = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
 
-error[E0308]: mismatched types
-  --> $DIR/fn-const-param-infer.rs:16:31
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/fn-const-param-infer.rs:4:25
    |
-LL |     let _: Checked<not_one> = Checked::<not_two>;
-   |                               ^^^^^^^^^^^^^^^^^^ expected `{not_one as fn(usize) -> bool}`, found `{not_two as fn(usize) -> bool}`
-   |
-   = note: expected type `{not_one as fn(usize) -> bool}`
-              found type `{not_two as fn(usize) -> bool}`
-
-error[E0308]: mismatched types
-  --> $DIR/fn-const-param-infer.rs:20:24
-   |
-LL |     let _ = Checked::<{generic_arg::<u32>}>;
-   |                        ^^^^^^^^^^^^^^^^^^ expected `usize`, found `u32`
-   |
-   = note: expected fn pointer `fn(usize) -> _`
-                 found fn item `fn(u32) -> _ {generic_arg::<u32>}`
-
-error[E0282]: type annotations needed
-  --> $DIR/fn-const-param-infer.rs:22:23
-   |
-LL |     let _ = Checked::<generic>;
-   |                       ^^^^^^^ cannot infer type for type parameter `T` declared on the function `generic`
-
-error[E0308]: mismatched types
-  --> $DIR/fn-const-param-infer.rs:25:40
-   |
-LL |     let _: Checked<{generic::<u32>}> = Checked::<{generic::<u16>}>;
-   |                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{generic::<u32> as fn(usize) -> bool}`, found `{generic::<u16> as fn(usize) -> bool}`
-   |
-   = note: expected type `{generic::<u32> as fn(usize) -> bool}`
-              found type `{generic::<u16> as fn(usize) -> bool}`
+LL | struct Checked<const F: fn(usize) -> bool>;
+   |                         ^^^^^^^^^^^^^^^^^
 
-error: aborting due to 4 previous errors; 1 warning emitted
+error: aborting due to previous error; 1 warning emitted
 
-Some errors have detailed explanations: E0282, E0308.
-For more information about an error, try `rustc --explain E0282`.
diff --git a/src/test/ui/const-generics/raw-ptr-const-param-deref.rs b/src/test/ui/const-generics/raw-ptr-const-param-deref.rs
index c498bfe2e97..97ca9d6a44c 100644
--- a/src/test/ui/const-generics/raw-ptr-const-param-deref.rs
+++ b/src/test/ui/const-generics/raw-ptr-const-param-deref.rs
@@ -1,12 +1,11 @@
-// run-pass
-#![feature(const_generics, const_compare_raw_pointers)]
+#![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete
 
 const A: u32 = 3;
 
-struct Const<const P: *const u32>;
+struct Const<const P: *const u32>; //~ ERROR: using raw pointers as const generic parameters
 
-impl<const P: *const u32> Const<P> {
+impl<const P: *const u32> Const<P> { //~ ERROR: using raw pointers as const generic parameters
     fn get() -> u32 {
         unsafe {
             *P
diff --git a/src/test/ui/const-generics/raw-ptr-const-param-deref.stderr b/src/test/ui/const-generics/raw-ptr-const-param-deref.stderr
index 1ffc63ffdac..1ce8bb9c054 100644
--- a/src/test/ui/const-generics/raw-ptr-const-param-deref.stderr
+++ b/src/test/ui/const-generics/raw-ptr-const-param-deref.stderr
@@ -1,11 +1,23 @@
 warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/raw-ptr-const-param-deref.rs:2:12
+  --> $DIR/raw-ptr-const-param-deref.rs:1:12
    |
-LL | #![feature(const_generics, const_compare_raw_pointers)]
+LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
    |
    = note: `#[warn(incomplete_features)]` on by default
    = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
 
-warning: 1 warning emitted
+error: using raw pointers as const generic parameters is forbidden
+  --> $DIR/raw-ptr-const-param-deref.rs:6:23
+   |
+LL | struct Const<const P: *const u32>;
+   |                       ^^^^^^^^^^
+
+error: using raw pointers as const generic parameters is forbidden
+  --> $DIR/raw-ptr-const-param-deref.rs:8:15
+   |
+LL | impl<const P: *const u32> Const<P> {
+   |               ^^^^^^^^^^
+
+error: aborting due to 2 previous errors; 1 warning emitted
 
diff --git a/src/test/ui/const-generics/raw-ptr-const-param.rs b/src/test/ui/const-generics/raw-ptr-const-param.rs
index d7d970e952b..237b410e073 100644
--- a/src/test/ui/const-generics/raw-ptr-const-param.rs
+++ b/src/test/ui/const-generics/raw-ptr-const-param.rs
@@ -1,9 +1,9 @@
-#![feature(const_generics, const_compare_raw_pointers)]
+#![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete
 
-struct Const<const P: *const u32>;
+struct Const<const P: *const u32>; //~ ERROR: using raw pointers as const generic parameters
 
 fn main() {
-    let _: Const<{ 15 as *const _ }> = Const::<{ 10 as *const _ }>; //~ mismatched types
+    let _: Const<{ 15 as *const _ }> = Const::<{ 10 as *const _ }>;
     let _: Const<{ 10 as *const _ }> = Const::<{ 10 as *const _ }>;
 }
diff --git a/src/test/ui/const-generics/raw-ptr-const-param.stderr b/src/test/ui/const-generics/raw-ptr-const-param.stderr
index 7a665397c12..6e64f8a327f 100644
--- a/src/test/ui/const-generics/raw-ptr-const-param.stderr
+++ b/src/test/ui/const-generics/raw-ptr-const-param.stderr
@@ -1,21 +1,17 @@
 warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
   --> $DIR/raw-ptr-const-param.rs:1:12
    |
-LL | #![feature(const_generics, const_compare_raw_pointers)]
+LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
    |
    = note: `#[warn(incomplete_features)]` on by default
    = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
 
-error[E0308]: mismatched types
-  --> $DIR/raw-ptr-const-param.rs:7:40
+error: using raw pointers as const generic parameters is forbidden
+  --> $DIR/raw-ptr-const-param.rs:4:23
    |
-LL |     let _: Const<{ 15 as *const _ }> = Const::<{ 10 as *const _ }>;
-   |                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{0xf as *const u32}`, found `{0xa as *const u32}`
-   |
-   = note: expected type `{0xf as *const u32}`
-              found type `{0xa as *const u32}`
+LL | struct Const<const P: *const u32>;
+   |                       ^^^^^^^^^^
 
 error: aborting due to previous error; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/consts/const-eval/const_raw_ptr_ops.rs b/src/test/ui/consts/const-eval/const_raw_ptr_ops.rs
index 9be1374f85d..91c4bc8972c 100644
--- a/src/test/ui/consts/const-eval/const_raw_ptr_ops.rs
+++ b/src/test/ui/consts/const-eval/const_raw_ptr_ops.rs
@@ -1,17 +1,6 @@
-#![feature(const_raw_ptr_to_usize_cast, const_compare_raw_pointers, const_raw_ptr_deref)]
-
 fn main() {}
 
 // unconst and bad, will thus error in miri
-const X: bool = unsafe { &1 as *const i32 == &2 as *const i32 }; //~ ERROR any use of this
-// unconst and bad, will thus error in miri
-const X2: bool = unsafe { 42 as *const i32 == 43 as *const i32 }; //~ ERROR any use of this
-// unconst and fine
-const Y: usize = unsafe { 42usize as *const i32 as usize + 1 };
-// unconst and bad, will thus error in miri
-const Y2: usize = unsafe { &1 as *const i32 as usize + 1 }; //~ ERROR any use of this
-// unconst and fine
-const Z: i32 = unsafe { *(&1 as *const i32) };
+const X: bool = unsafe { &1 as *const i32 == &2 as *const i32 }; //~ ERROR cannot be compared
 // unconst and bad, will thus error in miri
-const Z2: i32 = unsafe { *(42 as *const i32) }; //~ ERROR any use of this value will cause
-const Z3: i32 = unsafe { *(44 as *const i32) }; //~ ERROR any use of this value will cause
+const X2: bool = unsafe { 42 as *const i32 == 43 as *const i32 }; //~ ERROR cannot be compared
diff --git a/src/test/ui/consts/const-eval/const_raw_ptr_ops.stderr b/src/test/ui/consts/const-eval/const_raw_ptr_ops.stderr
index cc40728e6b5..dee555beca0 100644
--- a/src/test/ui/consts/const-eval/const_raw_ptr_ops.stderr
+++ b/src/test/ui/consts/const-eval/const_raw_ptr_ops.stderr
@@ -1,44 +1,20 @@
-error: any use of this value will cause an error
-  --> $DIR/const_raw_ptr_ops.rs:6:26
+error: pointers cannot be compared in a meaningful way during const eval.
+  --> $DIR/const_raw_ptr_ops.rs:4:26
    |
 LL | const X: bool = unsafe { &1 as *const i32 == &2 as *const i32 };
-   | -------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
-   |                          |
-   |                          "pointer arithmetic or comparison" needs an rfc before being allowed inside constants
+   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: `#[deny(const_err)]` on by default
+   = note: It is conceptually impossible for const eval to know in all cases whether two pointers are equal. While sometimes it is clear (the address of a static item is never equal to the address of another static item), comparing an integer address with any allocation's address is impossible to do at compile-time.
+   = note: That said, there's the `ptr_maybe_eq` intrinsic which returns `true` for all comparisons where CTFE isn't sure whether two addresses are equal. The mirror intrinsic `ptr_maybe_ne` returns `true` for all comparisons where CTFE isn't sure whether two addresses are inequal.
 
-error: any use of this value will cause an error
-  --> $DIR/const_raw_ptr_ops.rs:8:27
+error: pointers cannot be compared in a meaningful way during const eval.
+  --> $DIR/const_raw_ptr_ops.rs:6:27
    |
 LL | const X2: bool = unsafe { 42 as *const i32 == 43 as *const i32 };
-   | --------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
-   |                           |
-   |                           "pointer arithmetic or comparison" needs an rfc before being allowed inside constants
-
-error: any use of this value will cause an error
-  --> $DIR/const_raw_ptr_ops.rs:12:28
-   |
-LL | const Y2: usize = unsafe { &1 as *const i32 as usize + 1 };
-   | ---------------------------^^^^^^^^^^^^^^^^^^^^^^^^^-------
-   |                            |
-   |                            "pointer-to-integer cast" needs an rfc before being allowed inside constants
-
-error: any use of this value will cause an error
-  --> $DIR/const_raw_ptr_ops.rs:16:26
-   |
-LL | const Z2: i32 = unsafe { *(42 as *const i32) };
-   | -------------------------^^^^^^^^^^^^^^^^^^^---
-   |                          |
-   |                          unable to turn bytes into a pointer
-
-error: any use of this value will cause an error
-  --> $DIR/const_raw_ptr_ops.rs:17:26
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-LL | const Z3: i32 = unsafe { *(44 as *const i32) };
-   | -------------------------^^^^^^^^^^^^^^^^^^^---
-   |                          |
-   |                          unable to turn bytes into a pointer
+   = note: It is conceptually impossible for const eval to know in all cases whether two pointers are equal. While sometimes it is clear (the address of a static item is never equal to the address of another static item), comparing an integer address with any allocation's address is impossible to do at compile-time.
+   = note: That said, there's the `ptr_maybe_eq` intrinsic which returns `true` for all comparisons where CTFE isn't sure whether two addresses are equal. The mirror intrinsic `ptr_maybe_ne` returns `true` for all comparisons where CTFE isn't sure whether two addresses are inequal.
 
-error: aborting due to 5 previous errors
+error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/consts/const-eval/const_raw_ptr_ops2.rs b/src/test/ui/consts/const-eval/const_raw_ptr_ops2.rs
new file mode 100644
index 00000000000..d2a7623837a
--- /dev/null
+++ b/src/test/ui/consts/const-eval/const_raw_ptr_ops2.rs
@@ -0,0 +1,13 @@
+#![feature(const_raw_ptr_to_usize_cast, const_raw_ptr_deref)]
+
+fn main() {}
+
+// unconst and fine
+const Y: usize = unsafe { 42usize as *const i32 as usize + 1 };
+// unconst and bad, will thus error in miri
+const Y2: usize = unsafe { &1 as *const i32 as usize + 1 }; //~ ERROR any use of this
+// unconst and fine
+const Z: i32 = unsafe { *(&1 as *const i32) };
+// unconst and bad, will thus error in miri
+const Z2: i32 = unsafe { *(42 as *const i32) }; //~ ERROR any use of this value will cause
+const Z3: i32 = unsafe { *(44 as *const i32) }; //~ ERROR any use of this value will cause
diff --git a/src/test/ui/consts/const-eval/const_raw_ptr_ops2.stderr b/src/test/ui/consts/const-eval/const_raw_ptr_ops2.stderr
new file mode 100644
index 00000000000..93f2261745d
--- /dev/null
+++ b/src/test/ui/consts/const-eval/const_raw_ptr_ops2.stderr
@@ -0,0 +1,28 @@
+error: any use of this value will cause an error
+  --> $DIR/const_raw_ptr_ops2.rs:8:28
+   |
+LL | const Y2: usize = unsafe { &1 as *const i32 as usize + 1 };
+   | ---------------------------^^^^^^^^^^^^^^^^^^^^^^^^^-------
+   |                            |
+   |                            "pointer-to-integer cast" needs an rfc before being allowed inside constants
+   |
+   = note: `#[deny(const_err)]` on by default
+
+error: any use of this value will cause an error
+  --> $DIR/const_raw_ptr_ops2.rs:12:26
+   |
+LL | const Z2: i32 = unsafe { *(42 as *const i32) };
+   | -------------------------^^^^^^^^^^^^^^^^^^^---
+   |                          |
+   |                          unable to turn bytes into a pointer
+
+error: any use of this value will cause an error
+  --> $DIR/const_raw_ptr_ops2.rs:13:26
+   |
+LL | const Z3: i32 = unsafe { *(44 as *const i32) };
+   | -------------------------^^^^^^^^^^^^^^^^^^^---
+   |                          |
+   |                          unable to turn bytes into a pointer
+
+error: aborting due to 3 previous errors
+
diff --git a/src/test/ui/consts/const-eval/promoted_raw_ptr_ops.rs b/src/test/ui/consts/const-eval/promoted_raw_ptr_ops.rs
index c6fb5eeab5a..d724fe3060b 100644
--- a/src/test/ui/consts/const-eval/promoted_raw_ptr_ops.rs
+++ b/src/test/ui/consts/const-eval/promoted_raw_ptr_ops.rs
@@ -1,4 +1,4 @@
-#![feature(const_raw_ptr_to_usize_cast, const_compare_raw_pointers, const_raw_ptr_deref)]
+#![feature(const_raw_ptr_to_usize_cast, const_raw_ptr_deref)]
 
 fn main() {
     let x: &'static bool = &(42 as *const i32 == 43 as *const i32);
diff --git a/src/test/ui/consts/miri_unleashed/ptr_arith.stderr b/src/test/ui/consts/miri_unleashed/ptr_arith.stderr
index 4b3fe995700..c5d136ea97d 100644
--- a/src/test/ui/consts/miri_unleashed/ptr_arith.stderr
+++ b/src/test/ui/consts/miri_unleashed/ptr_arith.stderr
@@ -12,7 +12,7 @@ LL |     let _v = x + 0;
 
 warning: skipping const checks
    |
-help: skipping check for `const_compare_raw_pointers` feature
+help: skipping check that does not even have a feature gate
   --> $DIR/ptr_arith.rs:9:14
    |
 LL |     let _v = x == x;
diff --git a/src/test/ui/error-codes/E0395.rs b/src/test/ui/error-codes/E0395.rs
index bbefff27d7f..28fba1d3061 100644
--- a/src/test/ui/error-codes/E0395.rs
+++ b/src/test/ui/error-codes/E0395.rs
@@ -1,10 +1,8 @@
-// gate-test-const_compare_raw_pointers
-
 static FOO: i32 = 42;
 static BAR: i32 = 42;
 
 static BAZ: bool = unsafe { (&FOO as *const i32) == (&BAR as *const i32) };
-//~^ ERROR comparing raw pointers inside static
+//~^ ERROR pointers cannot be compared in a meaningful way during const eval
 
 fn main() {
 }
diff --git a/src/test/ui/error-codes/E0395.stderr b/src/test/ui/error-codes/E0395.stderr
index 20c8622f337..748126f7440 100644
--- a/src/test/ui/error-codes/E0395.stderr
+++ b/src/test/ui/error-codes/E0395.stderr
@@ -1,12 +1,11 @@
-error[E0658]: comparing raw pointers inside static
-  --> $DIR/E0395.rs:6:29
+error: pointers cannot be compared in a meaningful way during const eval.
+  --> $DIR/E0395.rs:4:29
    |
 LL | static BAZ: bool = unsafe { (&FOO as *const i32) == (&BAR as *const i32) };
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: see issue #53020 <https://github.com/rust-lang/rust/issues/53020> for more information
-   = help: add `#![feature(const_compare_raw_pointers)]` to the crate attributes to enable
+   = note: It is conceptually impossible for const eval to know in all cases whether two pointers are equal. While sometimes it is clear (the address of a static item is never equal to the address of another static item), comparing an integer address with any allocation's address is impossible to do at compile-time.
+   = note: That said, there's the `ptr_maybe_eq` intrinsic which returns `true` for all comparisons where CTFE isn't sure whether two addresses are equal. The mirror intrinsic `ptr_maybe_ne` returns `true` for all comparisons where CTFE isn't sure whether two addresses are inequal.
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/feature-gates/feature-gate-const_generics-ptr.rs b/src/test/ui/feature-gates/feature-gate-const_generics-ptr.rs
index 1ab11ce3b44..dc602ba7e6f 100644
--- a/src/test/ui/feature-gates/feature-gate-const_generics-ptr.rs
+++ b/src/test/ui/feature-gates/feature-gate-const_generics-ptr.rs
@@ -1,9 +1,9 @@
 struct ConstFn<const F: fn()>;
 //~^ ERROR const generics are unstable
-//~^^ ERROR using function pointers as const generic parameters is unstable
+//~^^ ERROR using function pointers as const generic parameters is forbidden
 
 struct ConstPtr<const P: *const u32>;
 //~^ ERROR const generics are unstable
-//~^^ ERROR using raw pointers as const generic parameters is unstable
+//~^^ ERROR using raw pointers as const generic parameters is forbidden
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-const_generics-ptr.stderr b/src/test/ui/feature-gates/feature-gate-const_generics-ptr.stderr
index dc7ef55e7ab..b2c96d3810f 100644
--- a/src/test/ui/feature-gates/feature-gate-const_generics-ptr.stderr
+++ b/src/test/ui/feature-gates/feature-gate-const_generics-ptr.stderr
@@ -16,23 +16,17 @@ LL | struct ConstPtr<const P: *const u32>;
    = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
    = help: add `#![feature(const_generics)]` to the crate attributes to enable
 
-error[E0658]: using function pointers as const generic parameters is unstable
+error: using function pointers as const generic parameters is forbidden
   --> $DIR/feature-gate-const_generics-ptr.rs:1:25
    |
 LL | struct ConstFn<const F: fn()>;
    |                         ^^^^
-   |
-   = note: see issue #53020 <https://github.com/rust-lang/rust/issues/53020> for more information
-   = help: add `#![feature(const_compare_raw_pointers)]` to the crate attributes to enable
 
-error[E0658]: using raw pointers as const generic parameters is unstable
+error: using raw pointers as const generic parameters is forbidden
   --> $DIR/feature-gate-const_generics-ptr.rs:5:26
    |
 LL | struct ConstPtr<const P: *const u32>;
    |                          ^^^^^^^^^^
-   |
-   = note: see issue #53020 <https://github.com/rust-lang/rust/issues/53020> for more information
-   = help: add `#![feature(const_compare_raw_pointers)]` to the crate attributes to enable
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/issues/issue-25826.rs b/src/test/ui/issues/issue-25826.rs
index 36a69cf4c22..cb0dfcfa953 100644
--- a/src/test/ui/issues/issue-25826.rs
+++ b/src/test/ui/issues/issue-25826.rs
@@ -1,6 +1,6 @@
 fn id<T>(t: T) -> T { t }
 fn main() {
     const A: bool = unsafe { id::<u8> as *const () < id::<u16> as *const () };
-    //~^ ERROR comparing raw pointers inside constant
+    //~^ ERROR pointers cannot be compared in a meaningful way during const eval
     println!("{}", A);
 }
diff --git a/src/test/ui/issues/issue-25826.stderr b/src/test/ui/issues/issue-25826.stderr
index 3a5a6b509ba..b3692098341 100644
--- a/src/test/ui/issues/issue-25826.stderr
+++ b/src/test/ui/issues/issue-25826.stderr
@@ -1,12 +1,11 @@
-error[E0658]: comparing raw pointers inside constant
+error: pointers cannot be compared in a meaningful way during const eval.
   --> $DIR/issue-25826.rs:3:30
    |
 LL |     const A: bool = unsafe { id::<u8> as *const () < id::<u16> as *const () };
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: see issue #53020 <https://github.com/rust-lang/rust/issues/53020> for more information
-   = help: add `#![feature(const_compare_raw_pointers)]` to the crate attributes to enable
+   = note: It is conceptually impossible for const eval to know in all cases whether two pointers are equal. While sometimes it is clear (the address of a static item is never equal to the address of another static item), comparing an integer address with any allocation's address is impossible to do at compile-time.
+   = note: That said, there's the `ptr_maybe_eq` intrinsic which returns `true` for all comparisons where CTFE isn't sure whether two addresses are equal. The mirror intrinsic `ptr_maybe_ne` returns `true` for all comparisons where CTFE isn't sure whether two addresses are inequal.
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/unsafe/unsafe-unstable-const-fn.rs b/src/test/ui/unsafe/unsafe-unstable-const-fn.rs
index d9d85ee9132..963d892931a 100644
--- a/src/test/ui/unsafe/unsafe-unstable-const-fn.rs
+++ b/src/test/ui/unsafe/unsafe-unstable-const-fn.rs
@@ -1,13 +1,13 @@
 #![stable(feature = "foo", since = "1.33.0")]
 #![feature(staged_api)]
-#![feature(const_compare_raw_pointers)]
+#![feature(const_raw_ptr_deref)]
 #![feature(const_fn)]
 
 #[stable(feature = "foo", since = "1.33.0")]
 #[rustc_const_unstable(feature = "const_foo", issue = "none")]
-const fn unstable(a: *const i32, b: *const i32) -> bool {
-    a == b
-    //~^ pointer operation is unsafe
+const fn unstable(a: *const i32, b: i32) -> bool {
+    *a == b
+    //~^ dereference of raw pointer is unsafe
 }
 
 fn main() {}
diff --git a/src/test/ui/unsafe/unsafe-unstable-const-fn.stderr b/src/test/ui/unsafe/unsafe-unstable-const-fn.stderr
index d8f3737c8f5..4642a7a5fc9 100644
--- a/src/test/ui/unsafe/unsafe-unstable-const-fn.stderr
+++ b/src/test/ui/unsafe/unsafe-unstable-const-fn.stderr
@@ -1,10 +1,10 @@
-error[E0133]: pointer operation is unsafe and requires unsafe function or block
+error[E0133]: dereference of raw pointer is unsafe and requires unsafe function or block
   --> $DIR/unsafe-unstable-const-fn.rs:9:5
    |
-LL |     a == b
-   |     ^^^^^^ pointer operation
+LL |     *a == b
+   |     ^^ dereference of raw pointer
    |
-   = note: operations on pointers in constants
+   = note: raw pointers may be NULL, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
 
 error: aborting due to previous error