diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index b3e43cd799405..540a8cfb290b3 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -1285,7 +1285,9 @@ extern "rust-intrinsic" {
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_transmute", issue = "53605")]
+    // NOTE: While this makes the intrinsic const stable, we have some custom code in const fn
+    // checks that prevent its use within `const fn`.
+    #[rustc_const_stable(feature = "const_transmute", since = "1.46.0")]
     pub fn transmute<T, U>(e: T) -> U;
 
     /// Returns `true` if the actual type given as `T` requires drop
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 692d91bd61ddf..820c0a49e7f03 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -140,7 +140,7 @@
 #![feature(rtm_target_feature)]
 #![feature(f16c_target_feature)]
 #![feature(hexagon_target_feature)]
-#![feature(const_transmute)]
+#![cfg_attr(not(bootstrap), feature(const_fn_transmute))]
 #![feature(abi_unadjusted)]
 #![feature(adx_target_feature)]
 #![feature(maybe_uninit_slice)]
diff --git a/src/librustc_ast/lib.rs b/src/librustc_ast/lib.rs
index ffd2aa61f2866..c32ed1ea48c97 100644
--- a/src/librustc_ast/lib.rs
+++ b/src/librustc_ast/lib.rs
@@ -10,7 +10,7 @@
 #![cfg_attr(bootstrap, feature(const_if_match))]
 #![feature(const_fn)] // For the `transmute` in `P::new`
 #![feature(const_panic)]
-#![feature(const_transmute)]
+#![cfg_attr(not(bootstrap), feature(const_fn_transmute))]
 #![feature(crate_visibility_modifier)]
 #![feature(label_break_value)]
 #![feature(nll)]
diff --git a/src/librustc_feature/active.rs b/src/librustc_feature/active.rs
index 32481bf2b9574..0da3693af4fb6 100644
--- a/src/librustc_feature/active.rs
+++ b/src/librustc_feature/active.rs
@@ -573,6 +573,9 @@ declare_features! (
     /// Lazily evaluate constants. This allows constants to depend on type parameters.
     (active, lazy_normalization_consts, "1.46.0", Some(72219), None),
 
+    /// Alloc calling `transmute` in const fn
+    (active, const_fn_transmute, "1.46.0", Some(53605), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------
diff --git a/src/librustc_middle/lib.rs b/src/librustc_middle/lib.rs
index 96b8ca27183ed..c2b14cb2e8408 100644
--- a/src/librustc_middle/lib.rs
+++ b/src/librustc_middle/lib.rs
@@ -30,7 +30,7 @@
 #![cfg_attr(bootstrap, feature(const_if_match))]
 #![feature(const_fn)]
 #![feature(const_panic)]
-#![feature(const_transmute)]
+#![cfg_attr(not(bootstrap), feature(const_fn_transmute))]
 #![feature(core_intrinsics)]
 #![feature(discriminant_kind)]
 #![feature(drain_filter)]
diff --git a/src/librustc_mir/transform/qualify_min_const_fn.rs b/src/librustc_mir/transform/qualify_min_const_fn.rs
index 7041e2db27e32..52b1eba3b93c2 100644
--- a/src/librustc_mir/transform/qualify_min_const_fn.rs
+++ b/src/librustc_mir/transform/qualify_min_const_fn.rs
@@ -6,6 +6,7 @@ use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::{self, adjustment::PointerCast, Ty, TyCtxt};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
+use rustc_target::spec::abi::Abi::RustIntrinsic;
 use std::borrow::Cow;
 
 type McfResult = Result<(), (Span, Cow<'static, str>)>;
@@ -418,6 +419,20 @@ fn check_terminator(
                     ));
                 }
 
+                // HACK: This is to "unstabilize" the `transmute` intrinsic
+                // within const fns. `transmute` is allowed in all other const contexts.
+                // This won't really scale to more intrinsics or functions. Let's allow const
+                // transmutes in const fn before we add more hacks to this.
+                if tcx.fn_sig(fn_def_id).abi() == RustIntrinsic
+                    && tcx.item_name(fn_def_id) == sym::transmute
+                    && !feature_allowed(tcx, def_id, sym::const_fn_transmute)
+                {
+                    return Err((
+                        span,
+                        "can only call `transmute` from const items, not `const fn`".into(),
+                    ));
+                }
+
                 check_operand(tcx, func, span, fn_def_id, body)?;
 
                 for arg in args {
diff --git a/src/librustc_span/symbol.rs b/src/librustc_span/symbol.rs
index 37fb7548e1d54..3c5521132135c 100644
--- a/src/librustc_span/symbol.rs
+++ b/src/librustc_span/symbol.rs
@@ -848,6 +848,7 @@ symbols! {
         track_caller,
         trait_alias,
         transmute,
+        const_fn_transmute,
         transparent,
         transparent_enums,
         transparent_unions,
diff --git a/src/test/ui/consts/const-eval/dangling.rs b/src/test/ui/consts/const-eval/dangling.rs
index c6b8e8eb61181..78cf000db03d1 100644
--- a/src/test/ui/consts/const-eval/dangling.rs
+++ b/src/test/ui/consts/const-eval/dangling.rs
@@ -1,4 +1,4 @@
-#![feature(const_transmute, const_raw_ptr_deref)]
+#![feature(const_raw_ptr_deref)]
 
 use std::{mem, usize};
 
diff --git a/src/test/ui/consts/const-eval/double_check.rs b/src/test/ui/consts/const-eval/double_check.rs
index f156d259abb20..56ca0aa1f1587 100644
--- a/src/test/ui/consts/const-eval/double_check.rs
+++ b/src/test/ui/consts/const-eval/double_check.rs
@@ -20,4 +20,6 @@ static FOO: (&Foo, &Bar) = unsafe {(
     Union { u8: &BAR }.bar,
 )};
 
+static FOO2: (&Foo, &Bar) = unsafe {(std::mem::transmute(&BAR), std::mem::transmute(&BAR))};
+
 fn main() {}
diff --git a/src/test/ui/consts/const-eval/double_check2.rs b/src/test/ui/consts/const-eval/double_check2.rs
index 7c222b113cd7d..8402d62885664 100644
--- a/src/test/ui/consts/const-eval/double_check2.rs
+++ b/src/test/ui/consts/const-eval/double_check2.rs
@@ -17,5 +17,7 @@ static FOO: (&Foo, &Bar) = unsafe {( //~ undefined behavior
     Union { u8: &BAR }.foo,
     Union { u8: &BAR }.bar,
 )};
+static FOO2: (&Foo, &Bar) = unsafe {(std::mem::transmute(&BAR), std::mem::transmute(&BAR))};
+//~^ undefined behavior
 
 fn main() {}
diff --git a/src/test/ui/consts/const-eval/double_check2.stderr b/src/test/ui/consts/const-eval/double_check2.stderr
index 513b71f0c6fdc..84f60809156d0 100644
--- a/src/test/ui/consts/const-eval/double_check2.stderr
+++ b/src/test/ui/consts/const-eval/double_check2.stderr
@@ -9,6 +9,14 @@ LL | | )};
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
-error: aborting due to previous error
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/double_check2.rs:20:1
+   |
+LL | static FOO2: (&Foo, &Bar) = unsafe {(std::mem::transmute(&BAR), std::mem::transmute(&BAR))};
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x05 at .1.<deref>.<enum-tag>, but expected a valid enum tag
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0080`.
diff --git a/src/test/ui/consts/const-eval/issue-55541.rs b/src/test/ui/consts/const-eval/issue-55541.rs
index 4c9e10d9cbe16..fa5a493abde21 100644
--- a/src/test/ui/consts/const-eval/issue-55541.rs
+++ b/src/test/ui/consts/const-eval/issue-55541.rs
@@ -2,7 +2,7 @@
 
 // Test that we can handle newtypes wrapping extern types
 
-#![feature(extern_types, const_transmute)]
+#![feature(extern_types)]
 
 use std::marker::PhantomData;
 
diff --git a/src/test/ui/consts/const-eval/transmute-const.rs b/src/test/ui/consts/const-eval/transmute-const.rs
index 48f2b39832e68..1cfad00ca76df 100644
--- a/src/test/ui/consts/const-eval/transmute-const.rs
+++ b/src/test/ui/consts/const-eval/transmute-const.rs
@@ -1,5 +1,3 @@
-#![feature(const_transmute)]
-
 use std::mem;
 
 static FOO: bool = unsafe { mem::transmute(3u8) };
diff --git a/src/test/ui/consts/const-eval/transmute-const.stderr b/src/test/ui/consts/const-eval/transmute-const.stderr
index 0de6ead4f525f..46a404982778d 100644
--- a/src/test/ui/consts/const-eval/transmute-const.stderr
+++ b/src/test/ui/consts/const-eval/transmute-const.stderr
@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/transmute-const.rs:5:1
+  --> $DIR/transmute-const.rs:3:1
    |
 LL | static FOO: bool = unsafe { mem::transmute(3u8) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x03, but expected a boolean
diff --git a/src/test/ui/consts/const-eval/ub-enum.rs b/src/test/ui/consts/const-eval/ub-enum.rs
index 136b33208c293..dc94f2368c9b6 100644
--- a/src/test/ui/consts/const-eval/ub-enum.rs
+++ b/src/test/ui/consts/const-eval/ub-enum.rs
@@ -1,5 +1,5 @@
 // normalize-stderr-64bit "0x0000000000" -> "0x00"
-#![feature(const_transmute, never_type)]
+#![feature(never_type)]
 #![allow(const_err)] // make sure we cannot allow away the errors tested here
 
 use std::mem;
diff --git a/src/test/ui/consts/const-eval/ub-int-array.rs b/src/test/ui/consts/const-eval/ub-int-array.rs
index 8907b0c160f88..6801c7fa3ff08 100644
--- a/src/test/ui/consts/const-eval/ub-int-array.rs
+++ b/src/test/ui/consts/const-eval/ub-int-array.rs
@@ -1,4 +1,3 @@
-#![feature(const_transmute)]
 #![allow(const_err)] // make sure we cannot allow away the errors tested here
 
 //! Test the "array of int" fast path in validity checking, and in particular whether it
diff --git a/src/test/ui/consts/const-eval/ub-int-array.stderr b/src/test/ui/consts/const-eval/ub-int-array.stderr
index b4a3c63b5a103..92f654847df32 100644
--- a/src/test/ui/consts/const-eval/ub-int-array.stderr
+++ b/src/test/ui/consts/const-eval/ub-int-array.stderr
@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-int-array.rs:15:1
+  --> $DIR/ub-int-array.rs:14:1
    |
 LL | / const UNINIT_INT_0: [u32; 3] = unsafe {
 LL | |
@@ -13,7 +13,7 @@ LL | | };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-int-array.rs:24:1
+  --> $DIR/ub-int-array.rs:23:1
    |
 LL | / const UNINIT_INT_1: [u32; 3] = unsafe {
 LL | |
@@ -27,7 +27,7 @@ LL | | };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-int-array.rs:44:1
+  --> $DIR/ub-int-array.rs:43:1
    |
 LL | / const UNINIT_INT_2: [u32; 3] = unsafe {
 LL | |
diff --git a/src/test/ui/consts/const-eval/ub-nonnull.rs b/src/test/ui/consts/const-eval/ub-nonnull.rs
index 1f46b6c98ad2f..4b90b892dce9a 100644
--- a/src/test/ui/consts/const-eval/ub-nonnull.rs
+++ b/src/test/ui/consts/const-eval/ub-nonnull.rs
@@ -1,4 +1,4 @@
-#![feature(rustc_attrs, const_transmute)]
+#![feature(rustc_attrs)]
 #![allow(const_err, invalid_value)] // make sure we cannot allow away the errors tested here
 
 use std::mem;
diff --git a/src/test/ui/consts/const-eval/ub-ref.rs b/src/test/ui/consts/const-eval/ub-ref.rs
index 10f4c8c03330e..e8b101fed6d2f 100644
--- a/src/test/ui/consts/const-eval/ub-ref.rs
+++ b/src/test/ui/consts/const-eval/ub-ref.rs
@@ -1,5 +1,4 @@
 // ignore-tidy-linelength
-#![feature(const_transmute)]
 #![allow(const_err, invalid_value)] // make sure we cannot allow away the errors tested here
 
 use std::mem;
diff --git a/src/test/ui/consts/const-eval/ub-ref.stderr b/src/test/ui/consts/const-eval/ub-ref.stderr
index a219679f18264..cd270f2a533bf 100644
--- a/src/test/ui/consts/const-eval/ub-ref.stderr
+++ b/src/test/ui/consts/const-eval/ub-ref.stderr
@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:7:1
+  --> $DIR/ub-ref.rs:6:1
    |
 LL | const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered an unaligned reference (required 2 byte alignment but found 1)
@@ -7,7 +7,7 @@ LL | const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:11:1
+  --> $DIR/ub-ref.rs:10:1
    |
 LL | const UNALIGNED_BOX: Box<u16> = unsafe { mem::transmute(&[0u8; 4]) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered an unaligned box (required 2 byte alignment but found 1)
@@ -15,7 +15,7 @@ LL | const UNALIGNED_BOX: Box<u16> = unsafe { mem::transmute(&[0u8; 4]) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:15:1
+  --> $DIR/ub-ref.rs:14:1
    |
 LL | const NULL: &u16 = unsafe { mem::transmute(0usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a NULL reference
@@ -23,7 +23,7 @@ LL | const NULL: &u16 = unsafe { mem::transmute(0usize) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:18:1
+  --> $DIR/ub-ref.rs:17:1
    |
 LL | const NULL_BOX: Box<u16> = unsafe { mem::transmute(0usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a NULL box
@@ -31,7 +31,7 @@ LL | const NULL_BOX: Box<u16> = unsafe { mem::transmute(0usize) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:24:1
+  --> $DIR/ub-ref.rs:23:1
    |
 LL | const REF_AS_USIZE: usize = unsafe { mem::transmute(&0) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc16, but expected initialized plain (non-pointer) bytes
@@ -39,7 +39,7 @@ LL | const REF_AS_USIZE: usize = unsafe { mem::transmute(&0) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:27:1
+  --> $DIR/ub-ref.rs:26:1
    |
 LL | const REF_AS_USIZE_SLICE: &[usize] = &[unsafe { mem::transmute(&0) }];
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at .<deref>, but expected plain (non-pointer) bytes
@@ -47,7 +47,7 @@ LL | const REF_AS_USIZE_SLICE: &[usize] = &[unsafe { mem::transmute(&0) }];
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:30:1
+  --> $DIR/ub-ref.rs:29:1
    |
 LL | const REF_AS_USIZE_BOX_SLICE: Box<[usize]> = unsafe { mem::transmute::<&[usize], _>(&[mem::transmute(&0)]) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at .<deref>, but expected plain (non-pointer) bytes
@@ -55,7 +55,7 @@ LL | const REF_AS_USIZE_BOX_SLICE: Box<[usize]> = unsafe { mem::transmute::<&[us
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:33:1
+  --> $DIR/ub-ref.rs:32:1
    |
 LL | const USIZE_AS_REF: &'static u8 = unsafe { mem::transmute(1337usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (created from integer)
@@ -63,7 +63,7 @@ LL | const USIZE_AS_REF: &'static u8 = unsafe { mem::transmute(1337usize) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-ref.rs:36:1
+  --> $DIR/ub-ref.rs:35:1
    |
 LL | const USIZE_AS_BOX: Box<u8> = unsafe { mem::transmute(1337usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling box (created from integer)
diff --git a/src/test/ui/consts/const-eval/ub-uninhabit.rs b/src/test/ui/consts/const-eval/ub-uninhabit.rs
index e7350ae271673..b81bca3849431 100644
--- a/src/test/ui/consts/const-eval/ub-uninhabit.rs
+++ b/src/test/ui/consts/const-eval/ub-uninhabit.rs
@@ -1,4 +1,3 @@
-#![feature(const_transmute)]
 #![allow(const_err)] // make sure we cannot allow away the errors tested here
 
 use std::mem;
diff --git a/src/test/ui/consts/const-eval/ub-uninhabit.stderr b/src/test/ui/consts/const-eval/ub-uninhabit.stderr
index 8ce4279a8b7dd..16f5316a44230 100644
--- a/src/test/ui/consts/const-eval/ub-uninhabit.stderr
+++ b/src/test/ui/consts/const-eval/ub-uninhabit.stderr
@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-uninhabit.rs:15:1
+  --> $DIR/ub-uninhabit.rs:14:1
    |
 LL | const BAD_BAD_BAD: Bar = unsafe { MaybeUninit { uninit: () }.init };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type Bar
@@ -7,7 +7,7 @@ LL | const BAD_BAD_BAD: Bar = unsafe { MaybeUninit { uninit: () }.init };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-uninhabit.rs:18:1
+  --> $DIR/ub-uninhabit.rs:17:1
    |
 LL | const BAD_BAD_REF: &Bar = unsafe { mem::transmute(1usize) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type Bar at .<deref>
@@ -15,7 +15,7 @@ LL | const BAD_BAD_REF: &Bar = unsafe { mem::transmute(1usize) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-uninhabit.rs:21:1
+  --> $DIR/ub-uninhabit.rs:20:1
    |
 LL | const BAD_BAD_ARRAY: [Bar; 1] = unsafe { MaybeUninit { uninit: () }.init };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type Bar at [0]
diff --git a/src/test/ui/consts/const-eval/ub-upvars.rs b/src/test/ui/consts/const-eval/ub-upvars.rs
index baab14dc16141..5d19276557eb6 100644
--- a/src/test/ui/consts/const-eval/ub-upvars.rs
+++ b/src/test/ui/consts/const-eval/ub-upvars.rs
@@ -1,4 +1,3 @@
-#![feature(const_transmute)]
 #![allow(const_err, invalid_value)] // make sure we cannot allow away the errors tested here
 
 use std::mem;
diff --git a/src/test/ui/consts/const-eval/ub-upvars.stderr b/src/test/ui/consts/const-eval/ub-upvars.stderr
index 972c9eb38c81e..afd6c9035cabf 100644
--- a/src/test/ui/consts/const-eval/ub-upvars.stderr
+++ b/src/test/ui/consts/const-eval/ub-upvars.stderr
@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-upvars.rs:6:1
+  --> $DIR/ub-upvars.rs:5:1
    |
 LL | / const BAD_UPVAR: &dyn FnOnce() = &{
 LL | |     let bad_ref: &'static u16 = unsafe { mem::transmute(0usize) };
diff --git a/src/test/ui/consts/const-eval/ub-wide-ptr.rs b/src/test/ui/consts/const-eval/ub-wide-ptr.rs
index f69f6a1109f76..3e148af8de9d5 100644
--- a/src/test/ui/consts/const-eval/ub-wide-ptr.rs
+++ b/src/test/ui/consts/const-eval/ub-wide-ptr.rs
@@ -1,5 +1,4 @@
 // ignore-tidy-linelength
-#![feature(const_transmute)]
 #![allow(unused)]
 #![allow(const_err)] // make sure we cannot allow away the errors tested here
 
diff --git a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
index 47d29ffc9b3c1..b7509108abc23 100644
--- a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
+++ b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:32:1
+  --> $DIR/ub-wide-ptr.rs:31:1
    |
 LL | const STR_TOO_LONG: &str = unsafe { mem::transmute((&42u8, 999usize)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (going beyond the bounds of its allocation)
@@ -7,7 +7,7 @@ LL | const STR_TOO_LONG: &str = unsafe { mem::transmute((&42u8, 999usize)) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:34:1
+  --> $DIR/ub-wide-ptr.rs:33:1
    |
 LL | const NESTED_STR_MUCH_TOO_LONG: (&str,) = (unsafe { mem::transmute((&42, usize::MAX)) },);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered invalid reference metadata: slice is bigger than largest supported object at .0
@@ -15,7 +15,7 @@ LL | const NESTED_STR_MUCH_TOO_LONG: (&str,) = (unsafe { mem::transmute((&42, us
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:37:1
+  --> $DIR/ub-wide-ptr.rs:36:1
    |
 LL | const STR_LENGTH_PTR: &str = unsafe { mem::transmute((&42u8, &3)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered non-integer slice length in wide pointer
@@ -23,7 +23,7 @@ LL | const STR_LENGTH_PTR: &str = unsafe { mem::transmute((&42u8, &3)) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:40:1
+  --> $DIR/ub-wide-ptr.rs:39:1
    |
 LL | const MY_STR_LENGTH_PTR: &MyStr = unsafe { mem::transmute((&42u8, &3)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered non-integer slice length in wide pointer
@@ -31,7 +31,7 @@ LL | const MY_STR_LENGTH_PTR: &MyStr = unsafe { mem::transmute((&42u8, &3)) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:42:1
+  --> $DIR/ub-wide-ptr.rs:41:1
    |
 LL | const MY_STR_MUCH_TOO_LONG: &MyStr = unsafe { mem::transmute((&42u8, usize::MAX)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered invalid reference metadata: slice is bigger than largest supported object
@@ -39,7 +39,7 @@ LL | const MY_STR_MUCH_TOO_LONG: &MyStr = unsafe { mem::transmute((&42u8, usize:
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:46:1
+  --> $DIR/ub-wide-ptr.rs:45:1
    |
 LL | const STR_NO_INIT: &str = unsafe { mem::transmute::<&[_], _>(&[MaybeUninit::<u8> { uninit: () }]) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized data in `str` at .<deref>
@@ -47,7 +47,7 @@ LL | const STR_NO_INIT: &str = unsafe { mem::transmute::<&[_], _>(&[MaybeUninit:
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:49:1
+  --> $DIR/ub-wide-ptr.rs:48:1
    |
 LL | const MYSTR_NO_INIT: &MyStr = unsafe { mem::transmute::<&[_], _>(&[MaybeUninit::<u8> { uninit: () }]) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized data in `str` at .<deref>.0
@@ -55,7 +55,7 @@ LL | const MYSTR_NO_INIT: &MyStr = unsafe { mem::transmute::<&[_], _>(&[MaybeUni
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:56:1
+  --> $DIR/ub-wide-ptr.rs:55:1
    |
 LL | / const SLICE_LENGTH_UNINIT: &[u8] = unsafe {
 LL | |
@@ -67,7 +67,7 @@ LL | | };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:62:1
+  --> $DIR/ub-wide-ptr.rs:61:1
    |
 LL | const SLICE_TOO_LONG: &[u8] = unsafe { mem::transmute((&42u8, 999usize)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (going beyond the bounds of its allocation)
@@ -75,7 +75,7 @@ LL | const SLICE_TOO_LONG: &[u8] = unsafe { mem::transmute((&42u8, 999usize)) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:65:1
+  --> $DIR/ub-wide-ptr.rs:64:1
    |
 LL | const SLICE_LENGTH_PTR: &[u8] = unsafe { mem::transmute((&42u8, &3)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered non-integer slice length in wide pointer
@@ -83,7 +83,7 @@ LL | const SLICE_LENGTH_PTR: &[u8] = unsafe { mem::transmute((&42u8, &3)) };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:68:1
+  --> $DIR/ub-wide-ptr.rs:67:1
    |
 LL | const SLICE_TOO_LONG_BOX: Box<[u8]> = unsafe { mem::transmute((&42u8, 999usize)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling box (going beyond the bounds of its allocation)
@@ -91,7 +91,7 @@ LL | const SLICE_TOO_LONG_BOX: Box<[u8]> = unsafe { mem::transmute((&42u8, 999us
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:71:1
+  --> $DIR/ub-wide-ptr.rs:70:1
    |
 LL | const SLICE_LENGTH_PTR_BOX: Box<[u8]> = unsafe { mem::transmute((&42u8, &3)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered non-integer slice length in wide pointer
@@ -99,7 +99,7 @@ LL | const SLICE_LENGTH_PTR_BOX: Box<[u8]> = unsafe { mem::transmute((&42u8, &3)
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:75:1
+  --> $DIR/ub-wide-ptr.rs:74:1
    |
 LL | const SLICE_CONTENT_INVALID: &[bool] = &[unsafe { mem::transmute(3u8) }];
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x03 at .<deref>[0], but expected a boolean
@@ -107,7 +107,7 @@ LL | const SLICE_CONTENT_INVALID: &[bool] = &[unsafe { mem::transmute(3u8) }];
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:81:1
+  --> $DIR/ub-wide-ptr.rs:80:1
    |
 LL | const MYSLICE_PREFIX_BAD: &MySliceBool = &MySlice(unsafe { mem::transmute(3u8) }, [false]);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x03 at .<deref>.0, but expected a boolean
@@ -115,7 +115,7 @@ LL | const MYSLICE_PREFIX_BAD: &MySliceBool = &MySlice(unsafe { mem::transmute(3
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:84:1
+  --> $DIR/ub-wide-ptr.rs:83:1
    |
 LL | const MYSLICE_SUFFIX_BAD: &MySliceBool = &MySlice(true, [unsafe { mem::transmute(3u8) }]);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x03 at .<deref>.1[0], but expected a boolean
@@ -123,7 +123,7 @@ LL | const MYSLICE_SUFFIX_BAD: &MySliceBool = &MySlice(true, [unsafe { mem::tran
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:91:1
+  --> $DIR/ub-wide-ptr.rs:90:1
    |
 LL | / const RAW_SLICE_LENGTH_UNINIT: *const [u8] = unsafe {
 LL | |
@@ -135,7 +135,7 @@ LL | | };
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:99:1
+  --> $DIR/ub-wide-ptr.rs:98:1
    |
 LL | const TRAIT_OBJ_SHORT_VTABLE_1: &dyn Trait = unsafe { mem::transmute((&92u8, &3u8)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered too small vtable
@@ -143,7 +143,7 @@ LL | const TRAIT_OBJ_SHORT_VTABLE_1: &dyn Trait = unsafe { mem::transmute((&92u8
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:102:1
+  --> $DIR/ub-wide-ptr.rs:101:1
    |
 LL | const TRAIT_OBJ_SHORT_VTABLE_2: &dyn Trait = unsafe { mem::transmute((&92u8, &3u64)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered too small vtable
@@ -151,7 +151,7 @@ LL | const TRAIT_OBJ_SHORT_VTABLE_2: &dyn Trait = unsafe { mem::transmute((&92u8
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:105:1
+  --> $DIR/ub-wide-ptr.rs:104:1
    |
 LL | const TRAIT_OBJ_INT_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, 4usize)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling vtable pointer in wide pointer
@@ -159,7 +159,7 @@ LL | const TRAIT_OBJ_INT_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, 4u
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:107:1
+  --> $DIR/ub-wide-ptr.rs:106:1
    |
 LL | const TRAIT_OBJ_UNALIGNED_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, &[0u8; 128])) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered unaligned vtable pointer in wide pointer
@@ -167,7 +167,7 @@ LL | const TRAIT_OBJ_UNALIGNED_VTABLE: &dyn Trait = unsafe { mem::transmute((&92
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:109:1
+  --> $DIR/ub-wide-ptr.rs:108:1
    |
 LL | const TRAIT_OBJ_BAD_DROP_FN_NULL: &dyn Trait = unsafe { mem::transmute((&92u8, &[0usize; 8])) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered invalid drop function pointer in vtable (not pointing to a function)
@@ -175,7 +175,7 @@ LL | const TRAIT_OBJ_BAD_DROP_FN_NULL: &dyn Trait = unsafe { mem::transmute((&92
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:111:1
+  --> $DIR/ub-wide-ptr.rs:110:1
    |
 LL | const TRAIT_OBJ_BAD_DROP_FN_INT: &dyn Trait = unsafe { mem::transmute((&92u8, &[1usize; 8])) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered invalid drop function pointer in vtable (not pointing to a function)
@@ -183,7 +183,7 @@ LL | const TRAIT_OBJ_BAD_DROP_FN_INT: &dyn Trait = unsafe { mem::transmute((&92u
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:113:1
+  --> $DIR/ub-wide-ptr.rs:112:1
    |
 LL | const TRAIT_OBJ_BAD_DROP_FN_NOT_FN_PTR: &dyn Trait = unsafe { mem::transmute((&92u8, &[&42u8; 8])) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered invalid drop function pointer in vtable (not pointing to a function)
@@ -191,7 +191,7 @@ LL | const TRAIT_OBJ_BAD_DROP_FN_NOT_FN_PTR: &dyn Trait = unsafe { mem::transmut
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:117:1
+  --> $DIR/ub-wide-ptr.rs:116:1
    |
 LL | const TRAIT_OBJ_CONTENT_INVALID: &dyn Trait = unsafe { mem::transmute::<_, &bool>(&3u8) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x03 at .<deref>.<dyn-downcast>, but expected a boolean
@@ -199,7 +199,7 @@ LL | const TRAIT_OBJ_CONTENT_INVALID: &dyn Trait = unsafe { mem::transmute::<_,
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:121:1
+  --> $DIR/ub-wide-ptr.rs:120:1
    |
 LL | const RAW_TRAIT_OBJ_VTABLE_NULL: *const dyn Trait = unsafe { mem::transmute((&92u8, 0usize)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling vtable pointer in wide pointer
@@ -207,7 +207,7 @@ LL | const RAW_TRAIT_OBJ_VTABLE_NULL: *const dyn Trait = unsafe { mem::transmute
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:123:1
+  --> $DIR/ub-wide-ptr.rs:122:1
    |
 LL | const RAW_TRAIT_OBJ_VTABLE_INVALID: *const dyn Trait = unsafe { mem::transmute((&92u8, &3u64)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered too small vtable
@@ -215,13 +215,13 @@ LL | const RAW_TRAIT_OBJ_VTABLE_INVALID: *const dyn Trait = unsafe { mem::transm
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: could not evaluate static initializer
-  --> $DIR/ub-wide-ptr.rs:129:5
+  --> $DIR/ub-wide-ptr.rs:128:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, 0usize))
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ inbounds test failed: 0x0 is not a valid pointer
 
 error[E0080]: could not evaluate static initializer
-  --> $DIR/ub-wide-ptr.rs:133:5
+  --> $DIR/ub-wide-ptr.rs:132:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, &3u64))
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: pointer must be in-bounds at offset N, but is outside bounds of allocN which has size N
diff --git a/src/test/ui/consts/const-eval/valid-const.rs b/src/test/ui/consts/const-eval/valid-const.rs
index 65c642d750b51..9e4707182d596 100644
--- a/src/test/ui/consts/const-eval/valid-const.rs
+++ b/src/test/ui/consts/const-eval/valid-const.rs
@@ -1,7 +1,6 @@
 // check-pass
 
 // Some constants that *are* valid
-#![feature(const_transmute)]
 #![deny(const_err)]
 
 use std::mem;
diff --git a/src/test/ui/consts/const-eval/validate_uninhabited_zsts.rs b/src/test/ui/consts/const-eval/validate_uninhabited_zsts.rs
index f18e00fd633ea..48a989bf58863 100644
--- a/src/test/ui/consts/const-eval/validate_uninhabited_zsts.rs
+++ b/src/test/ui/consts/const-eval/validate_uninhabited_zsts.rs
@@ -1,5 +1,5 @@
 #![feature(const_fn)]
-#![feature(const_transmute)]
+#![feature(const_fn_transmute)]
 
 const fn foo() -> ! {
     unsafe { std::mem::transmute(()) }
diff --git a/src/test/ui/consts/consts-in-patterns.rs b/src/test/ui/consts/consts-in-patterns.rs
index ee1e3cc22f77d..d51215447d6ca 100644
--- a/src/test/ui/consts/consts-in-patterns.rs
+++ b/src/test/ui/consts/consts-in-patterns.rs
@@ -1,5 +1,4 @@
 // run-pass
-#![feature(const_transmute)]
 
 const FOO: isize = 10;
 const BAR: isize = 3;
diff --git a/src/test/ui/consts/miri_unleashed/abi-mismatch.stderr b/src/test/ui/consts/miri_unleashed/abi-mismatch.stderr
index d55090c75e614..eb250081d6a72 100644
--- a/src/test/ui/consts/miri_unleashed/abi-mismatch.stderr
+++ b/src/test/ui/consts/miri_unleashed/abi-mismatch.stderr
@@ -17,11 +17,6 @@ help: skipping check that does not even have a feature gate
    |
 LL |     my_fn();
    |     ^^^^^^^
-help: skipping check that does not even have a feature gate
-  --> $DIR/abi-mismatch.rs:16:40
-   |
-LL | static VAL: () = call_rust_fn(unsafe { std::mem::transmute(c_fn as extern "C" fn()) });
-   |                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error; 1 warning emitted
 
diff --git a/src/test/ui/consts/miri_unleashed/ptr_arith.stderr b/src/test/ui/consts/miri_unleashed/ptr_arith.stderr
index 21f11dda5a667..d782a3633b243 100644
--- a/src/test/ui/consts/miri_unleashed/ptr_arith.stderr
+++ b/src/test/ui/consts/miri_unleashed/ptr_arith.stderr
@@ -17,11 +17,6 @@ help: skipping check that does not even have a feature gate
    |
 LL |     let _v = x == x;
    |              ^^^^^^
-help: skipping check that does not even have a feature gate
-  --> $DIR/ptr_arith.rs:15:20
-   |
-LL |     let x: usize = std::mem::transmute(&0);
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors; 1 warning emitted
 
diff --git a/src/test/ui/consts/transmute-const.rs b/src/test/ui/consts/transmute-const.rs
index e24f89cdffdff..5044d99ec5183 100644
--- a/src/test/ui/consts/transmute-const.rs
+++ b/src/test/ui/consts/transmute-const.rs
@@ -1,7 +1,5 @@
 // run-pass
 
-#![feature(const_transmute)]
-
 use std::mem;
 
 #[repr(transparent)]
diff --git a/src/test/ui/feature-gates/feature-gate-const_fn_transmute.rs b/src/test/ui/feature-gates/feature-gate-const_fn_transmute.rs
new file mode 100644
index 0000000000000..981680b5d1fad
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-const_fn_transmute.rs
@@ -0,0 +1,38 @@
+use std::mem;
+
+#[repr(transparent)]
+struct Foo(u32);
+
+const TRANSMUTED_U32: u32 = unsafe { mem::transmute(Foo(3)) };
+
+const fn transmute_fn() -> u32 { unsafe { mem::transmute(Foo(3)) } }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+
+const fn transmute_fn_intrinsic() -> u32 { unsafe { std::intrinsics::transmute(Foo(3)) } }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+
+const fn transmute_fn_core_intrinsic() -> u32 { unsafe { core::intrinsics::transmute(Foo(3)) } }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+
+const unsafe fn unsafe_transmute_fn() -> u32 { mem::transmute(Foo(3)) }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+
+const unsafe fn unsafe_transmute_fn_intrinsic() -> u32 { std::intrinsics::transmute(Foo(3)) }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+
+const unsafe fn unsafe_transmute_fn_core_intrinsic() -> u32 { core::intrinsics::transmute(Foo(3)) }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+
+const fn safe_transmute_fn() -> u32 { mem::transmute(Foo(3)) }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+//~| ERROR call to unsafe function is unsafe and requires unsafe function or block
+
+const fn safe_transmute_fn_intrinsic() -> u32 { std::intrinsics::transmute(Foo(3)) }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+//~| ERROR call to unsafe function is unsafe and requires unsafe function or block
+
+const fn safe_transmute_fn_core_intrinsic() -> u32 { core::intrinsics::transmute(Foo(3)) }
+//~^ ERROR can only call `transmute` from const items, not `const fn`
+//~| ERROR call to unsafe function is unsafe and requires unsafe function or block
+
+fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-const_fn_transmute.stderr b/src/test/ui/feature-gates/feature-gate-const_fn_transmute.stderr
new file mode 100644
index 0000000000000..44430fd577d88
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-const_fn_transmute.stderr
@@ -0,0 +1,109 @@
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:8:43
+   |
+LL | const fn transmute_fn() -> u32 { unsafe { mem::transmute(Foo(3)) } }
+   |                                           ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:11:53
+   |
+LL | const fn transmute_fn_intrinsic() -> u32 { unsafe { std::intrinsics::transmute(Foo(3)) } }
+   |                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:14:58
+   |
+LL | const fn transmute_fn_core_intrinsic() -> u32 { unsafe { core::intrinsics::transmute(Foo(3)) } }
+   |                                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:17:48
+   |
+LL | const unsafe fn unsafe_transmute_fn() -> u32 { mem::transmute(Foo(3)) }
+   |                                                ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:20:58
+   |
+LL | const unsafe fn unsafe_transmute_fn_intrinsic() -> u32 { std::intrinsics::transmute(Foo(3)) }
+   |                                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:23:63
+   |
+LL | const unsafe fn unsafe_transmute_fn_core_intrinsic() -> u32 { core::intrinsics::transmute(Foo(3)) }
+   |                                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:26:39
+   |
+LL | const fn safe_transmute_fn() -> u32 { mem::transmute(Foo(3)) }
+   |                                       ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:30:49
+   |
+LL | const fn safe_transmute_fn_intrinsic() -> u32 { std::intrinsics::transmute(Foo(3)) }
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0723]: can only call `transmute` from const items, not `const fn`
+  --> $DIR/feature-gate-const_fn_transmute.rs:34:54
+   |
+LL | const fn safe_transmute_fn_core_intrinsic() -> u32 { core::intrinsics::transmute(Foo(3)) }
+   |                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn)]` to the crate attributes to enable
+
+error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
+  --> $DIR/feature-gate-const_fn_transmute.rs:26:39
+   |
+LL | const fn safe_transmute_fn() -> u32 { mem::transmute(Foo(3)) }
+   |                                       ^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
+  --> $DIR/feature-gate-const_fn_transmute.rs:30:49
+   |
+LL | const fn safe_transmute_fn_intrinsic() -> u32 { std::intrinsics::transmute(Foo(3)) }
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
+  --> $DIR/feature-gate-const_fn_transmute.rs:34:54
+   |
+LL | const fn safe_transmute_fn_core_intrinsic() -> u32 { core::intrinsics::transmute(Foo(3)) }
+   |                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to 12 previous errors
+
+Some errors have detailed explanations: E0133, E0723.
+For more information about an error, try `rustc --explain E0133`.
diff --git a/src/test/ui/feature-gates/feature-gate-const_transmute.rs b/src/test/ui/feature-gates/feature-gate-const_transmute.rs
deleted file mode 100644
index da532643d9457..0000000000000
--- a/src/test/ui/feature-gates/feature-gate-const_transmute.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-use std::mem;
-
-#[repr(transparent)]
-struct Foo(u32);
-
-const TRANSMUTED_U32: u32 = unsafe { mem::transmute(Foo(3)) };
-//~^ ERROR `std::intrinsics::transmute` is not yet stable as a const fn
-
-fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-const_transmute.stderr b/src/test/ui/feature-gates/feature-gate-const_transmute.stderr
deleted file mode 100644
index 772e8d294781a..0000000000000
--- a/src/test/ui/feature-gates/feature-gate-const_transmute.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: `std::intrinsics::transmute` is not yet stable as a const fn
-  --> $DIR/feature-gate-const_transmute.rs:6:38
-   |
-LL | const TRANSMUTED_U32: u32 = unsafe { mem::transmute(Foo(3)) };
-   |                                      ^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = help: add `#![feature(const_transmute)]` to the crate attributes to enable
-
-error: aborting due to previous error
-
diff --git a/src/test/ui/internal/internal-unstable-const.rs b/src/test/ui/internal/internal-unstable-const.rs
index 3b3a2950942d0..b923bc22f6e5f 100644
--- a/src/test/ui/internal/internal-unstable-const.rs
+++ b/src/test/ui/internal/internal-unstable-const.rs
@@ -8,7 +8,7 @@
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 pub const fn foo() -> i32 {
-    unsafe { std::mem::transmute(4u32) } //~ ERROR is not stable as `const fn`
+    unsafe { std::mem::transmute(4u32) } //~ ERROR can only call `transmute` from const items
 }
 
 fn main() {}
diff --git a/src/test/ui/internal/internal-unstable-const.stderr b/src/test/ui/internal/internal-unstable-const.stderr
index 5a2c58f3928dc..9626df23ec3c2 100644
--- a/src/test/ui/internal/internal-unstable-const.stderr
+++ b/src/test/ui/internal/internal-unstable-const.stderr
@@ -1,4 +1,4 @@
-error[E0723]: can only call other `const fn` within a `const fn`, but `const std::intrinsics::transmute::<u32, i32>` is not stable as `const fn`
+error[E0723]: can only call `transmute` from const items, not `const fn`
   --> $DIR/internal-unstable-const.rs:11:14
    |
 LL |     unsafe { std::mem::transmute(4u32) }
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr
index 8dde56cd79f44..74d32b8a1aa93 100644
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr
+++ b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr
@@ -57,14 +57,6 @@ LL | |     t
 LL | | }
    | |_^
 
-error: this could be a `const fn`
-  --> $DIR/could_be_const.rs:48:1
-   |
-LL | / fn sub(x: u32) -> usize {
-LL | |     unsafe { transmute(&x) }
-LL | | }
-   | |_^
-
 error: this could be a `const fn`
   --> $DIR/could_be_const.rs:67:9
    |
@@ -73,5 +65,5 @@ LL | |             B
 LL | |         }
    | |_________^
 
-error: aborting due to 9 previous errors
+error: aborting due to 8 previous errors