Rollup merge of #128596 - RalfJung:const_fn_floating_point_arithmetic, r=nnethercote

stabilize const_fn_floating_point_arithmetic

Part of https://github.com/rust-lang/rust/issues/128288
Fixes https://github.com/rust-lang/rust/issues/57241

The existing test `tests/ui/consts/const_let_eq_float.rs`  ([link](https://github.com/RalfJung/rust/blob/const_fn_floating_point_arithmetic/tests/ui/consts/const_let_eq_float.rs)) covers the basics, and also Miri has extensive tests covering the interpreter's float machinery. Also, that machinery can already be used on stable inside `const`/`static` initializers, just not inside `const fn`.

This was explicitly called out in https://github.com/rust-lang/rfcs/pull/3514 so in a sense t-lang just recently already FCP'd this, but let's hear from them whether they want another FCP for the stabilization here or whether that was covered by the FCP for the RFC.
Cc ``@rust-lang/lang``

### Open items

- [x] Update the Reference: https://github.com/rust-lang/reference/pull/1566

27 files changed, 92 insertions, 257 deletions

diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index 86a5afa65ba..c80b3e673b0 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -575,10 +575,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             Rvalue::UnaryOp(_, operand) => {
                 let ty = operand.ty(self.body, self.tcx);
-                if is_int_bool_or_char(ty) {
-                    // Int, bool, and char operations are fine.
-                } else if ty.is_floating_point() {
-                    self.check_op(ops::FloatingPointOp);
+                if is_int_bool_float_or_char(ty) {
+                    // Int, bool, float, and char operations are fine.
                 } else {
                     span_bug!(self.span, "non-primitive type in `Rvalue::UnaryOp`: {:?}", ty);
                 }
@@ -588,8 +586,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 let lhs_ty = lhs.ty(self.body, self.tcx);
                 let rhs_ty = rhs.ty(self.body, self.tcx);
 
-                if is_int_bool_or_char(lhs_ty) && is_int_bool_or_char(rhs_ty) {
-                    // Int, bool, and char operations are fine.
+                if is_int_bool_float_or_char(lhs_ty) && is_int_bool_float_or_char(rhs_ty) {
+                    // Int, bool, float, and char operations are fine.
                 } else if lhs_ty.is_fn_ptr() || lhs_ty.is_unsafe_ptr() {
                     assert_matches!(
                         op,
@@ -603,8 +601,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     );
 
                     self.check_op(ops::RawPtrComparison);
-                } else if lhs_ty.is_floating_point() || rhs_ty.is_floating_point() {
-                    self.check_op(ops::FloatingPointOp);
                 } else {
                     span_bug!(
                         self.span,
@@ -1009,8 +1005,8 @@ fn place_as_reborrow<'tcx>(
     }
 }
 
-fn is_int_bool_or_char(ty: Ty<'_>) -> bool {
-    ty.is_bool() || ty.is_integral() || ty.is_char()
+fn is_int_bool_float_or_char(ty: Ty<'_>) -> bool {
+    ty.is_bool() || ty.is_integral() || ty.is_char() || ty.is_floating_point()
 }
 
 fn emit_unstable_in_stable_error(ccx: &ConstCx<'_, '_>, span: Span, gate: Symbol) {
diff --git a/compiler/rustc_const_eval/src/check_consts/ops.rs b/compiler/rustc_const_eval/src/check_consts/ops.rs
index 259114dbdc2..93fafa60557 100644
--- a/compiler/rustc_const_eval/src/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/check_consts/ops.rs
@@ -55,28 +55,6 @@ pub trait NonConstOp<'tcx>: std::fmt::Debug {
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx>;
 }
 
-#[derive(Debug)]
-pub struct FloatingPointOp;
-impl<'tcx> NonConstOp<'tcx> for FloatingPointOp {
-    fn status_in_item(&self, ccx: &ConstCx<'_, 'tcx>) -> Status {
-        if ccx.const_kind() == hir::ConstContext::ConstFn {
-            Status::Unstable(sym::const_fn_floating_point_arithmetic)
-        } else {
-            Status::Allowed
-        }
-    }
-
-    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
-    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        feature_err(
-            &ccx.tcx.sess,
-            sym::const_fn_floating_point_arithmetic,
-            span,
-            format!("floating point arithmetic is not allowed in {}s", ccx.const_kind()),
-        )
-    }
-}
-
 /// A function call where the callee is a pointer.
 #[derive(Debug)]
 pub struct FnCallIndirect;
@@ -440,22 +418,12 @@ impl<'tcx> NonConstOp<'tcx> for CellBorrow {
         DiagImportance::Secondary
     }
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        // FIXME: Maybe a more elegant solution to this if else case
-        if let hir::ConstContext::Static(_) = ccx.const_kind() {
-            ccx.dcx().create_err(errors::InteriorMutableDataRefer {
-                span,
-                opt_help: true,
-                kind: ccx.const_kind(),
-                teach: ccx.tcx.sess.teach(E0492),
-            })
-        } else {
-            ccx.dcx().create_err(errors::InteriorMutableDataRefer {
-                span,
-                opt_help: false,
-                kind: ccx.const_kind(),
-                teach: ccx.tcx.sess.teach(E0492),
-            })
-        }
+        ccx.dcx().create_err(errors::InteriorMutableDataRefer {
+            span,
+            opt_help: matches!(ccx.const_kind(), hir::ConstContext::Static(_)),
+            kind: ccx.const_kind(),
+            teach: ccx.tcx.sess.teach(E0492),
+        })
     }
 }
 
diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index a4a2028e26e..9223c3c322a 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -115,6 +115,8 @@ declare_features! (
     (accepted, conservative_impl_trait, "1.26.0", Some(34511)),
     /// Allows calling constructor functions in `const fn`.
     (accepted, const_constructor, "1.40.0", Some(61456)),
+    /// Allows basic arithmetic on floating point types in a `const fn`.
+    (accepted, const_fn_floating_point_arithmetic, "CURRENT_RUSTC_VERSION", Some(57241)),
     /// Allows using and casting function pointers in a `const fn`.
     (accepted, const_fn_fn_ptr_basics, "1.61.0", Some(57563)),
     /// Allows trait bounds in `const fn`.
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index a1741ac33ca..3a143c52a8c 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -400,8 +400,6 @@ declare_features! (
     (incomplete, const_closures, "1.68.0", Some(106003)),
     /// Allows the definition of `const extern fn` and `const unsafe extern fn`.
     (unstable, const_extern_fn, "1.40.0", Some(64926)),
-    /// Allows basic arithmetic on floating point types in a `const fn`.
-    (unstable, const_fn_floating_point_arithmetic, "1.48.0", Some(57241)),
     /// Allows `for _ in _` loops in const contexts.
     (unstable, const_for, "1.56.0", Some(87575)),
     /// Allows using `&mut` in constant functions.
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index bbfe412fbcf..7f0efede240 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -193,6 +193,7 @@
 // Language features:
 // tidy-alphabetical-start
 #![cfg_attr(bootstrap, feature(asm_const))]
+#![cfg_attr(bootstrap, feature(const_fn_floating_point_arithmetic))]
 #![cfg_attr(bootstrap, feature(min_exhaustive_patterns))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
@@ -202,7 +203,6 @@
 #![feature(cfg_sanitize)]
 #![feature(cfg_target_has_atomic)]
 #![feature(cfg_target_has_atomic_equal_alignment)]
-#![feature(const_fn_floating_point_arithmetic)]
 #![feature(const_for)]
 #![feature(const_mut_refs)]
 #![feature(const_precise_live_drops)]
diff --git a/src/tools/clippy/tests/ui/floating_point_abs.fixed b/src/tools/clippy/tests/ui/floating_point_abs.fixed
index 5312a8b29c6..33183c76972 100644
--- a/src/tools/clippy/tests/ui/floating_point_abs.fixed
+++ b/src/tools/clippy/tests/ui/floating_point_abs.fixed
@@ -1,4 +1,3 @@
-#![feature(const_fn_floating_point_arithmetic)]
 #![warn(clippy::suboptimal_flops)]
 
 /// Allow suboptimal ops in constant context
diff --git a/src/tools/clippy/tests/ui/floating_point_abs.rs b/src/tools/clippy/tests/ui/floating_point_abs.rs
index 8619177130c..a08d5bbcef5 100644
--- a/src/tools/clippy/tests/ui/floating_point_abs.rs
+++ b/src/tools/clippy/tests/ui/floating_point_abs.rs
@@ -1,4 +1,3 @@
-#![feature(const_fn_floating_point_arithmetic)]
 #![warn(clippy::suboptimal_flops)]
 
 /// Allow suboptimal ops in constant context
diff --git a/src/tools/clippy/tests/ui/floating_point_abs.stderr b/src/tools/clippy/tests/ui/floating_point_abs.stderr
index f5a778c5b76..0c1f68f3b7f 100644
--- a/src/tools/clippy/tests/ui/floating_point_abs.stderr
+++ b/src/tools/clippy/tests/ui/floating_point_abs.stderr
@@ -1,5 +1,5 @@
 error: manual implementation of `abs` method
-  --> tests/ui/floating_point_abs.rs:15:5
+  --> tests/ui/floating_point_abs.rs:14:5
    |
 LL |     if num >= 0.0 { num } else { -num }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.abs()`
@@ -8,43 +8,43 @@ LL |     if num >= 0.0 { num } else { -num }
    = help: to override `-D warnings` add `#[allow(clippy::suboptimal_flops)]`
 
 error: manual implementation of `abs` method
-  --> tests/ui/floating_point_abs.rs:19:5
+  --> tests/ui/floating_point_abs.rs:18:5
    |
 LL |     if 0.0 < num { num } else { -num }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.abs()`
 
 error: manual implementation of `abs` method
-  --> tests/ui/floating_point_abs.rs:23:5
+  --> tests/ui/floating_point_abs.rs:22:5
    |
 LL |     if a.a > 0.0 { a.a } else { -a.a }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `a.a.abs()`
 
 error: manual implementation of `abs` method
-  --> tests/ui/floating_point_abs.rs:27:5
+  --> tests/ui/floating_point_abs.rs:26:5
    |
 LL |     if 0.0 >= num { -num } else { num }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.abs()`
 
 error: manual implementation of `abs` method
-  --> tests/ui/floating_point_abs.rs:31:5
+  --> tests/ui/floating_point_abs.rs:30:5
    |
 LL |     if a.a < 0.0 { -a.a } else { a.a }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `a.a.abs()`
 
 error: manual implementation of negation of `abs` method
-  --> tests/ui/floating_point_abs.rs:35:5
+  --> tests/ui/floating_point_abs.rs:34:5
    |
 LL |     if num < 0.0 { num } else { -num }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `-num.abs()`
 
 error: manual implementation of negation of `abs` method
-  --> tests/ui/floating_point_abs.rs:39:5
+  --> tests/ui/floating_point_abs.rs:38:5
    |
 LL |     if 0.0 >= num { num } else { -num }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `-num.abs()`
 
 error: manual implementation of negation of `abs` method
-  --> tests/ui/floating_point_abs.rs:44:12
+  --> tests/ui/floating_point_abs.rs:43:12
    |
 LL |         a: if a.a >= 0.0 { -a.a } else { a.a },
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `-a.a.abs()`
diff --git a/src/tools/clippy/tests/ui/floating_point_mul_add.fixed b/src/tools/clippy/tests/ui/floating_point_mul_add.fixed
index 3ce2edf2c71..164aac2601a 100644
--- a/src/tools/clippy/tests/ui/floating_point_mul_add.fixed
+++ b/src/tools/clippy/tests/ui/floating_point_mul_add.fixed
@@ -1,4 +1,3 @@
-#![feature(const_fn_floating_point_arithmetic)]
 #![warn(clippy::suboptimal_flops)]
 
 /// Allow suboptimal_ops in constant context
diff --git a/src/tools/clippy/tests/ui/floating_point_mul_add.rs b/src/tools/clippy/tests/ui/floating_point_mul_add.rs
index b5e4a8db4db..ae024b7f224 100644
--- a/src/tools/clippy/tests/ui/floating_point_mul_add.rs
+++ b/src/tools/clippy/tests/ui/floating_point_mul_add.rs
@@ -1,4 +1,3 @@
-#![feature(const_fn_floating_point_arithmetic)]
 #![warn(clippy::suboptimal_flops)]
 
 /// Allow suboptimal_ops in constant context
diff --git a/src/tools/clippy/tests/ui/floating_point_mul_add.stderr b/src/tools/clippy/tests/ui/floating_point_mul_add.stderr
index 3e1a071de73..9c75909f715 100644
--- a/src/tools/clippy/tests/ui/floating_point_mul_add.stderr
+++ b/src/tools/clippy/tests/ui/floating_point_mul_add.stderr
@@ -1,5 +1,5 @@
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:20:13
+  --> tests/ui/floating_point_mul_add.rs:19:13
    |
 LL |     let _ = a * b + c;
    |             ^^^^^^^^^ help: consider using: `a.mul_add(b, c)`
@@ -8,73 +8,73 @@ LL |     let _ = a * b + c;
    = help: to override `-D warnings` add `#[allow(clippy::suboptimal_flops)]`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:21:13
+  --> tests/ui/floating_point_mul_add.rs:20:13
    |
 LL |     let _ = a * b - c;
    |             ^^^^^^^^^ help: consider using: `a.mul_add(b, -c)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:22:13
+  --> tests/ui/floating_point_mul_add.rs:21:13
    |
 LL |     let _ = c + a * b;
    |             ^^^^^^^^^ help: consider using: `a.mul_add(b, c)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:23:13
+  --> tests/ui/floating_point_mul_add.rs:22:13
    |
 LL |     let _ = c - a * b;
    |             ^^^^^^^^^ help: consider using: `a.mul_add(-b, c)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:24:13
+  --> tests/ui/floating_point_mul_add.rs:23:13
    |
 LL |     let _ = a + 2.0 * 4.0;
    |             ^^^^^^^^^^^^^ help: consider using: `2.0f64.mul_add(4.0, a)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:25:13
+  --> tests/ui/floating_point_mul_add.rs:24:13
    |
 LL |     let _ = a + 2. * 4.;
    |             ^^^^^^^^^^^ help: consider using: `2.0f64.mul_add(4., a)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:27:13
+  --> tests/ui/floating_point_mul_add.rs:26:13
    |
 LL |     let _ = (a * b) + c;
    |             ^^^^^^^^^^^ help: consider using: `a.mul_add(b, c)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:28:13
+  --> tests/ui/floating_point_mul_add.rs:27:13
    |
 LL |     let _ = c + (a * b);
    |             ^^^^^^^^^^^ help: consider using: `a.mul_add(b, c)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:29:13
+  --> tests/ui/floating_point_mul_add.rs:28:13
    |
 LL |     let _ = a * b * c + d;
    |             ^^^^^^^^^^^^^ help: consider using: `(a * b).mul_add(c, d)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:31:13
+  --> tests/ui/floating_point_mul_add.rs:30:13
    |
 LL |     let _ = a.mul_add(b, c) * a.mul_add(b, c) + a.mul_add(b, c) + c;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `a.mul_add(b, c).mul_add(a.mul_add(b, c), a.mul_add(b, c))`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:32:13
+  --> tests/ui/floating_point_mul_add.rs:31:13
    |
 LL |     let _ = 1234.567_f64 * 45.67834_f64 + 0.0004_f64;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `1234.567_f64.mul_add(45.67834_f64, 0.0004_f64)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:34:13
+  --> tests/ui/floating_point_mul_add.rs:33:13
    |
 LL |     let _ = (a * a + b).sqrt();
    |             ^^^^^^^^^^^ help: consider using: `a.mul_add(a, b)`
 
 error: multiply and add expressions can be calculated more efficiently and accurately
-  --> tests/ui/floating_point_mul_add.rs:37:13
+  --> tests/ui/floating_point_mul_add.rs:36:13
    |
 LL |     let _ = a - (b * u as f64);
    |             ^^^^^^^^^^^^^^^^^^ help: consider using: `b.mul_add(-(u as f64), a)`
diff --git a/src/tools/clippy/tests/ui/floating_point_rad.fixed b/src/tools/clippy/tests/ui/floating_point_rad.fixed
index a710bd9bd60..2f93d233cb4 100644
--- a/src/tools/clippy/tests/ui/floating_point_rad.fixed
+++ b/src/tools/clippy/tests/ui/floating_point_rad.fixed
@@ -1,4 +1,3 @@
-#![feature(const_fn_floating_point_arithmetic)]
 #![warn(clippy::suboptimal_flops)]
 
 /// Allow suboptimal_flops in constant context
diff --git a/src/tools/clippy/tests/ui/floating_point_rad.rs b/src/tools/clippy/tests/ui/floating_point_rad.rs
index 14656f021df..9690effc4e1 100644
--- a/src/tools/clippy/tests/ui/floating_point_rad.rs
+++ b/src/tools/clippy/tests/ui/floating_point_rad.rs
@@ -1,4 +1,3 @@
-#![feature(const_fn_floating_point_arithmetic)]
 #![warn(clippy::suboptimal_flops)]
 
 /// Allow suboptimal_flops in constant context
diff --git a/src/tools/clippy/tests/ui/floating_point_rad.stderr b/src/tools/clippy/tests/ui/floating_point_rad.stderr
index 64674342c2b..b834f5374e0 100644
--- a/src/tools/clippy/tests/ui/floating_point_rad.stderr
+++ b/src/tools/clippy/tests/ui/floating_point_rad.stderr
@@ -1,5 +1,5 @@
 error: conversion to radians can be done more accurately
-  --> tests/ui/floating_point_rad.rs:11:13
+  --> tests/ui/floating_point_rad.rs:10:13
    |
 LL |     let _ = degrees as f64 * std::f64::consts::PI / 180.0;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(degrees as f64).to_radians()`
@@ -8,43 +8,43 @@ LL |     let _ = degrees as f64 * std::f64::consts::PI / 180.0;
    = help: to override `-D warnings` add `#[allow(clippy::suboptimal_flops)]`
 
 error: conversion to degrees can be done more accurately
-  --> tests/ui/floating_point_rad.rs:12:13
+  --> tests/ui/floating_point_rad.rs:11:13
    |
 LL |     let _ = degrees as f64 * 180.0 / std::f64::consts::PI;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(degrees as f64).to_degrees()`
 
 error: conversion to degrees can be done more accurately
-  --> tests/ui/floating_point_rad.rs:17:13
+  --> tests/ui/floating_point_rad.rs:16:13
    |
 LL |     let _ = x * 180f32 / std::f32::consts::PI;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.to_degrees()`
 
 error: conversion to degrees can be done more accurately
-  --> tests/ui/floating_point_rad.rs:18:13
+  --> tests/ui/floating_point_rad.rs:17:13
    |
 LL |     let _ = 90. * 180f64 / std::f64::consts::PI;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `90.0_f64.to_degrees()`
 
 error: conversion to degrees can be done more accurately
-  --> tests/ui/floating_point_rad.rs:19:13
+  --> tests/ui/floating_point_rad.rs:18:13
    |
 LL |     let _ = 90.5 * 180f64 / std::f64::consts::PI;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `90.5_f64.to_degrees()`
 
 error: conversion to radians can be done more accurately
-  --> tests/ui/floating_point_rad.rs:20:13
+  --> tests/ui/floating_point_rad.rs:19:13
    |
 LL |     let _ = x * std::f32::consts::PI / 180f32;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.to_radians()`
 
 error: conversion to radians can be done more accurately
-  --> tests/ui/floating_point_rad.rs:21:13
+  --> tests/ui/floating_point_rad.rs:20:13
    |
 LL |     let _ = 90. * std::f32::consts::PI / 180f32;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `90.0_f64.to_radians()`
 
 error: conversion to radians can be done more accurately
-  --> tests/ui/floating_point_rad.rs:22:13
+  --> tests/ui/floating_point_rad.rs:21:13
    |
 LL |     let _ = 90.5 * std::f32::consts::PI / 180f32;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `90.5_f64.to_radians()`
diff --git a/tests/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs b/tests/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs
index c7078e46fa6..efc0a1c2fba 100644
--- a/tests/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs
+++ b/tests/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs
@@ -1,9 +1,5 @@
 #![feature(const_extern_fn)]
 
-const extern "C" fn unsize(x: &[u8; 3]) -> &[u8] { x }
-const unsafe extern "C" fn closure() -> fn() { || {} }
-const unsafe extern "C" fn use_float() { 1.0 + 1.0; }
-//~^ ERROR floating point arithmetic
 const extern "C" fn ptr_cast(val: *const u8) { val as usize; }
 //~^ ERROR pointers cannot be cast to integers
 
diff --git a/tests/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr b/tests/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
index 29fa90d611c..9cdeec159be 100644
--- a/tests/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
+++ b/tests/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr
@@ -1,15 +1,5 @@
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/const-extern-fn-min-const-fn.rs:5:42
-   |
-LL | const unsafe extern "C" fn use_float() { 1.0 + 1.0; }
-   |                                          ^^^^^^^^^
-   |
-   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
 error: pointers cannot be cast to integers during const eval
-  --> $DIR/const-extern-fn-min-const-fn.rs:7:48
+  --> $DIR/const-extern-fn-min-const-fn.rs:3:48
    |
 LL | const extern "C" fn ptr_cast(val: *const u8) { val as usize; }
    |                                                ^^^^^^^^^^^^
@@ -17,6 +7,5 @@ LL | const extern "C" fn ptr_cast(val: *const u8) { val as usize; }
    = note: at compile-time, pointers do not have an integer value
    = note: avoiding this restriction via `transmute`, `union`, or raw pointers leads to compile-time undefined behavior
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/consts/const-extern-fn/const-extern-fn.rs b/tests/ui/consts/const-extern-fn/const-extern-fn.rs
index 57f5da8d0af..4b164767064 100644
--- a/tests/ui/consts/const-extern-fn/const-extern-fn.rs
+++ b/tests/ui/consts/const-extern-fn/const-extern-fn.rs
@@ -17,6 +17,19 @@ const unsafe extern "C" fn bar2(val: bool) -> bool {
     !val
 }
 
+#[allow(improper_ctypes_definitions)]
+const extern "C" fn unsize(x: &[u8; 3]) -> &[u8] {
+    x
+}
+
+#[allow(improper_ctypes_definitions)]
+const unsafe extern "C" fn closure() -> fn() {
+    || {}
+}
+
+const unsafe extern "C" fn use_float() -> f32 {
+    1.0 + 1.0
+}
 
 fn main() {
     let a: [u8; foo1(25) as usize] = [0; 26];
@@ -32,4 +45,8 @@ fn main() {
     let _foo2_cast: extern "C" fn(u8) -> u8 = foo2;
     let _bar1_cast: unsafe extern "C" fn(bool) -> bool = bar1;
     let _bar2_cast: unsafe extern "C" fn(bool) -> bool = bar2;
+
+    unsize(&[0, 1, 2]);
+    unsafe { closure(); }
+    unsafe { use_float(); }
 }
diff --git a/tests/ui/consts/const_fn_floating_point_arithmetic.gated.stderr b/tests/ui/consts/const_fn_floating_point_arithmetic.gated.stderr
deleted file mode 100644
index e1b8154a287..00000000000
--- a/tests/ui/consts/const_fn_floating_point_arithmetic.gated.stderr
+++ /dev/null
@@ -1,8 +0,0 @@
-error: fatal error triggered by #[rustc_error]
-  --> $DIR/const_fn_floating_point_arithmetic.rs:20:1
-   |
-LL | fn main() {}
-   | ^^^^^^^^^
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/consts/const_fn_floating_point_arithmetic.rs b/tests/ui/consts/const_fn_floating_point_arithmetic.rs
deleted file mode 100644
index b0d0bc6b9f4..00000000000
--- a/tests/ui/consts/const_fn_floating_point_arithmetic.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-// gate-test-const_fn_floating_point_arithmetic
-
-//@ revisions: stock gated
-
-#![feature(rustc_attrs)]
-#![cfg_attr(gated, feature(const_fn_floating_point_arithmetic))]
-
-const fn add(f: f32) -> f32 { f + 2.0 }
-//[stock]~^ floating point arithmetic
-const fn sub(f: f32) -> f32 { 2.0 - f }
-//[stock]~^ floating point arithmetic
-const fn mul(f: f32, g: f32) -> f32 { f * g }
-//[stock]~^ floating point arithmetic
-const fn div(f: f32, g: f32) -> f32 { f / g }
-//[stock]~^ floating point arithmetic
-const fn neg(f: f32) -> f32 { -f }
-//[stock]~^ floating point arithmetic
-
-#[rustc_error]
-fn main() {} //[gated]~ fatal error triggered by #[rustc_error]
diff --git a/tests/ui/consts/const_fn_floating_point_arithmetic.stock.stderr b/tests/ui/consts/const_fn_floating_point_arithmetic.stock.stderr
deleted file mode 100644
index b5b94786ebb..00000000000
--- a/tests/ui/consts/const_fn_floating_point_arithmetic.stock.stderr
+++ /dev/null
@@ -1,53 +0,0 @@
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/const_fn_floating_point_arithmetic.rs:8:31
-   |
-LL | const fn add(f: f32) -> f32 { f + 2.0 }
-   |                               ^^^^^^^
-   |
-   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/const_fn_floating_point_arithmetic.rs:10:31
-   |
-LL | const fn sub(f: f32) -> f32 { 2.0 - f }
-   |                               ^^^^^^^
-   |
-   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/const_fn_floating_point_arithmetic.rs:12:39
-   |
-LL | const fn mul(f: f32, g: f32) -> f32 { f * g }
-   |                                       ^^^^^
-   |
-   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/const_fn_floating_point_arithmetic.rs:14:39
-   |
-LL | const fn div(f: f32, g: f32) -> f32 { f / g }
-   |                                       ^^^^^
-   |
-   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error[E0658]: floating point arithmetic is not allowed in constant functions
-  --> $DIR/const_fn_floating_point_arithmetic.rs:16:31
-   |
-LL | const fn neg(f: f32) -> f32 { -f }
-   |                               ^^
-   |
-   = note: see issue #57241 <https://github.com/rust-lang/rust/issues/57241> for more information
-   = help: add `#![feature(const_fn_floating_point_arithmetic)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error: aborting due to 5 previous errors
-
-For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/consts/const_let_eq_float.rs b/tests/ui/consts/const_let_eq_float.rs
index 30d839cdc2a..c9ca6b8b7ea 100644
--- a/tests/ui/consts/const_let_eq_float.rs
+++ b/tests/ui/consts/const_let_eq_float.rs
@@ -1,7 +1,5 @@
 //@ run-pass
 
-#![feature(const_fn_floating_point_arithmetic)]
-
 struct Foo<T>(T);
 struct Bar<T> { x: T }
 struct W(f32);
diff --git a/tests/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs b/tests/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
index bb240fb4ad6..dc653370e51 100644
--- a/tests/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
+++ b/tests/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
@@ -3,7 +3,7 @@
             we're apparently really bad at it",
             issue = "none")]
 
-#![feature(const_fn_floating_point_arithmetic, foo, foo2)]
+#![feature(const_refs_to_cell, foo, foo2)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -25,9 +25,13 @@ const fn bar2() -> u32 { foo2() } //~ ERROR not yet stable as a const fn
 
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "rust1", since = "1.0.0")]
-// Const-stable functions cannot rely on unstable const-eval features.
-const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
-//~^ ERROR const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
+// conformity is required
+const fn bar3() -> u32 {
+    let x = std::cell::Cell::new(0u32);
+    x.get()
+    //~^ ERROR const-stable function cannot use `#[feature(const_refs_to_cell)]`
+    //~| ERROR cannot call non-const fn
+}
 
 // check whether this function cannot be called even with the feature gate active
 #[unstable(feature = "foo2", issue = "none")]
diff --git a/tests/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr b/tests/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
index 7ec2508ca93..e5f8fa25b64 100644
--- a/tests/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
+++ b/tests/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
@@ -14,30 +14,39 @@ LL | const fn bar2() -> u32 { foo2() }
    |
    = help: const-stable functions can only call other const-stable functions
 
-error: const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
-  --> $DIR/min_const_fn_libstd_stability.rs:29:26
+error: const-stable function cannot use `#[feature(const_refs_to_cell)]`
+  --> $DIR/min_const_fn_libstd_stability.rs:31:5
    |
-LL | const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
-   |                          ^^^^^^^^^^^^^
+LL |     x.get()
+   |     ^
    |
 help: if it is not part of the public API, make this function unstably const
    |
 LL + #[rustc_const_unstable(feature = "...", issue = "...")]
-LL | const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
+LL | const fn bar3() -> u32 {
    |
 help: otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks
    |
-LL + #[rustc_allow_const_fn_unstable(const_fn_floating_point_arithmetic)]
-LL | const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
+LL + #[rustc_allow_const_fn_unstable(const_refs_to_cell)]
+LL | const fn bar3() -> u32 {
    |
 
+error[E0015]: cannot call non-const fn `Cell::<u32>::get` in constant functions
+  --> $DIR/min_const_fn_libstd_stability.rs:31:7
+   |
+LL |     x.get()
+   |       ^^^^^
+   |
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+
 error: `foo2_gated` is not yet stable as a const fn
-  --> $DIR/min_const_fn_libstd_stability.rs:39:32
+  --> $DIR/min_const_fn_libstd_stability.rs:43:32
    |
 LL | const fn bar2_gated() -> u32 { foo2_gated() }
    |                                ^^^^^^^^^^^^
    |
    = help: const-stable functions can only call other const-stable functions
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0015`.
diff --git a/tests/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs b/tests/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
index 03084c8674d..f2a54b8a13d 100644
--- a/tests/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
+++ b/tests/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
@@ -3,7 +3,7 @@
             we're apparently really bad at it",
             issue = "none")]
 
-#![feature(const_fn_floating_point_arithmetic, foo, foo2)]
+#![feature(const_refs_to_cell, foo, foo2)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -23,12 +23,6 @@ const unsafe fn foo2() -> u32 { 42 }
 // can't call non-min_const_fn
 const unsafe fn bar2() -> u32 { unsafe { foo2() } } //~ ERROR not yet stable as a const fn
 
-#[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
-// conformity is required
-const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }
-//~^ ERROR const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
-
 // check whether this function cannot be called even with the feature gate active
 #[unstable(feature = "foo2", issue = "none")]
 const unsafe fn foo2_gated() -> u32 { 42 }
diff --git a/tests/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr b/tests/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
index 72c1f175d1d..353b117efbc 100644
--- a/tests/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
+++ b/tests/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
@@ -14,30 +14,13 @@ LL | const unsafe fn bar2() -> u32 { unsafe { foo2() } }
    |
    = help: const-stable functions can only call other const-stable functions
 
-error: const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
-  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:29:33
-   |
-LL | const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }
-   |                                 ^^^^^^^^^^^^^
-   |
-help: if it is not part of the public API, make this function unstably const
-   |
-LL + #[rustc_const_unstable(feature = "...", issue = "...")]
-LL | const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }
-   |
-help: otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks
-   |
-LL + #[rustc_allow_const_fn_unstable(const_fn_floating_point_arithmetic)]
-LL | const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }
-   |
-
 error: `foo2_gated` is not yet stable as a const fn
-  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:39:48
+  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:33:48
    |
 LL | const unsafe fn bar2_gated() -> u32 { unsafe { foo2_gated() } }
    |                                                ^^^^^^^^^^^^
    |
    = help: const-stable functions can only call other const-stable functions
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
diff --git a/tests/ui/internal/internal-unstable-const.rs b/tests/ui/internal/internal-unstable-const.rs
deleted file mode 100644
index 4ec2426dfee..00000000000
--- a/tests/ui/internal/internal-unstable-const.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-// Don't allow unstable features in stable functions without `allow_internal_unstable`.
-
-#![stable(feature = "rust1", since = "1.0.0")]
-#![feature(staged_api)]
-#![feature(const_fn_floating_point_arithmetic)]
-
-#[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
-pub const fn foo() -> f32 {
-    1.0 + 1.0 //~ ERROR const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
-}
-
-fn main() {}
diff --git a/tests/ui/internal/internal-unstable-const.stderr b/tests/ui/internal/internal-unstable-const.stderr
deleted file mode 100644
index ed9196d2b63..00000000000
--- a/tests/ui/internal/internal-unstable-const.stderr
+++ /dev/null
@@ -1,19 +0,0 @@
-error: const-stable function cannot use `#[feature(const_fn_floating_point_arithmetic)]`
-  --> $DIR/internal-unstable-const.rs:10:5
-   |
-LL |     1.0 + 1.0
-   |     ^^^^^^^^^
-   |
-help: if it is not part of the public API, make this function unstably const
-   |
-LL + #[rustc_const_unstable(feature = "...", issue = "...")]
-LL | pub const fn foo() -> f32 {
-   |
-help: otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks
-   |
-LL + #[rustc_allow_const_fn_unstable(const_fn_floating_point_arithmetic)]
-LL | pub const fn foo() -> f32 {
-   |
-
-error: aborting due to 1 previous error
-