Stabilize float::to_int_unchecked

This renames and stabilizes unsafe floating point to integer casts, which are
intended to be the substitute for the currently unsound `as` behavior, once that
changes to safe-but-slower saturating casts.

Author: Mark-Simulacrum

src/libcore/convert/num.rs

@@ -13,9 +13,9 @@ mod private {
 /// Typically doesn’t need to be used directly.
 #[unstable(feature = "convert_float_to_int", issue = "67057")]
 pub trait FloatToInt<Int>: private::Sealed + Sized {
-    #[unstable(feature = "float_approx_unchecked_to", issue = "67058")]
+    #[unstable(feature = "convert_float_to_int", issue = "67057")]
     #[doc(hidden)]
-    unsafe fn approx_unchecked(self) -> Int;
+    unsafe fn to_int_unchecked(self) -> Int;
 }
 
 macro_rules! impl_float_to_int {
@@ -27,8 +27,15 @@ macro_rules! impl_float_to_int {
             impl FloatToInt<$Int> for $Float {
                 #[doc(hidden)]
                 #[inline]
-                unsafe fn approx_unchecked(self) -> $Int {
-                    crate::intrinsics::float_to_int_approx_unchecked(self)
+                unsafe fn to_int_unchecked(self) -> $Int {
+                    #[cfg(bootstrap)]
+                    {
+                        crate::intrinsics::float_to_int_approx_unchecked(self)
+                    }
+                    #[cfg(not(bootstrap))]
+                    {
+                        crate::intrinsics::float_to_int_unchecked(self)
+                    }
                 }
             }
         )+

src/libcore/intrinsics.rs

@@ -1582,8 +1582,16 @@ extern "rust-intrinsic" {
     /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
     /// (<https://github.com/rust-lang/rust/issues/10184>)
     /// This is under stabilization at <https://github.com/rust-lang/rust/issues/67058>
+    #[cfg(bootstrap)]
     pub fn float_to_int_approx_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
 
+    /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
+    /// (<https://github.com/rust-lang/rust/issues/10184>)
+    ///
+    /// Stabilized as `f32::to_int_unchecked` and `f64::to_int_unchecked`.
+    #[cfg(not(bootstrap))]
+    pub fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+
     /// Returns the number of bits set in an integer type `T`
     ///
     /// The stabilized versions of this intrinsic are available on the integer

src/libcore/num/f32.rs

@@ -464,14 +464,12 @@ impl f32 {
     /// assuming that the value is finite and fits in that type.
     ///
     /// ```
-    /// #![feature(float_approx_unchecked_to)]
-    ///
     /// let value = 4.6_f32;
-    /// let rounded = unsafe { value.approx_unchecked_to::<u16>() };
+    /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
     /// assert_eq!(rounded, 4);
     ///
     /// let value = -128.9_f32;
-    /// let rounded = unsafe { value.approx_unchecked_to::<i8>() };
+    /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
     /// assert_eq!(rounded, std::i8::MIN);
     /// ```
     ///
@@ -482,13 +480,13 @@ impl f32 {
     /// * Not be `NaN`
     /// * Not be infinite
     /// * Be representable in the return type `Int`, after truncating off its fractional part
-    #[unstable(feature = "float_approx_unchecked_to", issue = "67058")]
+    #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
     #[inline]
-    pub unsafe fn approx_unchecked_to<Int>(self) -> Int
+    pub unsafe fn to_int_unchecked<Int>(self) -> Int
     where
         Self: FloatToInt<Int>,
     {
-        FloatToInt::<Int>::approx_unchecked(self)
+        FloatToInt::<Int>::to_int_unchecked(self)
     }
 
     /// Raw transmutation to `u32`.

src/libcore/num/f64.rs

@@ -478,14 +478,12 @@ impl f64 {
     /// assuming that the value is finite and fits in that type.
     ///
     /// ```
-    /// #![feature(float_approx_unchecked_to)]
-    ///
     /// let value = 4.6_f32;
-    /// let rounded = unsafe { value.approx_unchecked_to::<u16>() };
+    /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
     /// assert_eq!(rounded, 4);
     ///
     /// let value = -128.9_f32;
-    /// let rounded = unsafe { value.approx_unchecked_to::<i8>() };
+    /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
     /// assert_eq!(rounded, std::i8::MIN);
     /// ```
     ///
@@ -496,13 +494,13 @@ impl f64 {
     /// * Not be `NaN`
     /// * Not be infinite
     /// * Be representable in the return type `Int`, after truncating off its fractional part
-    #[unstable(feature = "float_approx_unchecked_to", issue = "67058")]
+    #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
     #[inline]
-    pub unsafe fn approx_unchecked_to<Int>(self) -> Int
+    pub unsafe fn to_int_unchecked<Int>(self) -> Int
     where
         Self: FloatToInt<Int>,
     {
-        FloatToInt::<Int>::approx_unchecked(self)
+        FloatToInt::<Int>::to_int_unchecked(self)
     }
 
     /// Raw transmutation to `u64`.

src/librustc_codegen_llvm/intrinsic.rs

@@ -544,13 +544,13 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 }
             }
 
-            "float_to_int_approx_unchecked" => {
+            "float_to_int_unchecked" => {
                 if float_type_width(arg_tys[0]).is_none() {
                     span_invalid_monomorphization_error(
                         tcx.sess,
                         span,
                         &format!(
-                            "invalid monomorphization of `float_to_int_approx_unchecked` \
+                            "invalid monomorphization of `float_to_int_unchecked` \
                                   intrinsic: expected basic float type, \
                                   found `{}`",
                             arg_tys[0]
@@ -571,7 +571,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                             tcx.sess,
                             span,
                             &format!(
-                                "invalid monomorphization of `float_to_int_approx_unchecked` \
+                                "invalid monomorphization of `float_to_int_unchecked` \
                                       intrinsic:  expected basic integer type, \
                                       found `{}`",
                                 ret_ty

src/librustc_typeck/check/intrinsic.rs

@@ -275,7 +275,7 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
             "fadd_fast" | "fsub_fast" | "fmul_fast" | "fdiv_fast" | "frem_fast" => {
                 (1, vec![param(0), param(0)], param(0))
             }
-            "float_to_int_approx_unchecked" => (2, vec![param(0)], param(1)),
+            "float_to_int_unchecked" => (2, vec![param(0)], param(1)),
 
             "assume" => (0, vec![tcx.types.bool], tcx.mk_unit()),
             "likely" => (0, vec![tcx.types.bool], tcx.types.bool),