#[stable(feature = "rust1", since = "1.0.0")]
mod prim_unit {}
+// Required to make auto trait impls render.
+// See src/librustdoc/passes/collect_trait_impls.rs:collect_trait_impls
+#[doc(hidden)]
+impl () {}
+
+// Fake impl that's only really used for docs.
+#[cfg(doc)]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Clone for () {
+ fn clone(&self) -> Self {
+ loop {}
+ }
+}
+
+// Fake impl that's only really used for docs.
+#[cfg(doc)]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Copy for () {
+ // empty
+}
+
#[doc(primitive = "pointer")]
#[doc(alias = "ptr")]
#[doc(alias = "*")]
///
/// For more about tuples, see [the book](../book/ch03-02-data-types.html#the-tuple-type).
///
+// Hardcoded anchor in src/librustdoc/html/format.rs
+// linked to as `#trait-implementations-1`
/// # Trait implementations
///
-/// If every type inside a tuple implements one of the following traits, then a
-/// tuple itself also implements it.
+/// In this documentation the shorthand `(T₁, T₂, …, Tₙ)` is used to represent tuples of varying
+/// length. When that is used, any trait bound expressed on `T` applies to each element of the
+/// tuple independently. Note that this is a convenience notation to avoid repetitive
+/// documentation, not valid Rust syntax.
+///
+/// Due to a temporary restriction in Rust’s type system, the following traits are only
+/// implemented on tuples of arity 12 or less. In the future, this may change:
///
-/// * [`Clone`]
-/// * [`Copy`]
/// * [`PartialEq`]
/// * [`Eq`]
/// * [`PartialOrd`]
/// [`Debug`]: fmt::Debug
/// [`Hash`]: hash::Hash
///
-/// Due to a temporary restriction in Rust's type system, these traits are only
-/// implemented on tuples of arity 12 or less. In the future, this may change.
+/// The following traits are implemented for tuples of any length. These traits have
+/// implementations that are automatically generated by the compiler, so are not limited by
+/// missing language features.
+///
+/// * [`Clone`]
+/// * [`Copy`]
+/// * [`Send`]
+/// * [`Sync`]
+/// * [`Unpin`]
+/// * [`UnwindSafe`]
+/// * [`RefUnwindSafe`]
+///
+/// [`Unpin`]: marker::Unpin
+/// [`UnwindSafe`]: panic::UnwindSafe
+/// [`RefUnwindSafe`]: panic::RefUnwindSafe
///
/// # Examples
///
#[stable(feature = "rust1", since = "1.0.0")]
mod prim_tuple {}
+// Required to make auto trait impls render.
+// See src/librustdoc/passes/collect_trait_impls.rs:collect_trait_impls
+#[doc(hidden)]
+impl<T> (T,) {}
+
+// Fake impl that's only really used for docs.
+#[cfg(doc)]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(tuple_variadic))]
+/// This trait is implemented on arbitrary-length tuples.
+impl<T: Clone> Clone for (T,) {
+ fn clone(&self) -> Self {
+ loop {}
+ }
+}
+
+// Fake impl that's only really used for docs.
+#[cfg(doc)]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(tuple_variadic))]
+/// This trait is implemented on arbitrary-length tuples.
+impl<T: Copy> Copy for (T,) {
+ // empty
+}
+
#[doc(primitive = "f32")]
/// A 32-bit floating point type (specifically, the "binary32" type defined in IEEE 754-2008).
///
/// surprising results upon inspecting the bit patterns,
/// as the same calculations might produce NaNs with different bit patterns.
///
+/// When the number resulting from a primitive operation (addition,
+/// subtraction, multiplication, or division) on this type is not exactly
+/// representable as `f32`, it is rounded according to the roundTiesToEven
+/// direction defined in IEEE 754-2008. That means:
+///
+/// - The result is the representable value closest to the true value, if there
+/// is a unique closest representable value.
+/// - If the true value is exactly half-way between two representable values,
+/// the result is the one with an even least-significant binary digit.
+/// - If the true value's magnitude is ≥ `f32::MAX` + 2<sup>(`f32::MAX_EXP` −
+/// `f32::MANTISSA_DIGITS` − 1)</sup>, the result is ∞ or −∞ (preserving the
+/// true value's sign).
+///
/// For more information on floating point numbers, see [Wikipedia][wikipedia].
///
/// *[See also the `std::f32::consts` module](crate::f32::consts).*
/// is a reference to the function-specific ZST. `&bar` is basically never what you
/// want when `bar` is a function.
///
+/// ### Casting to and from integers
+///
+/// You cast function pointers directly to integers:
+///
+/// ```rust
+/// let fnptr: fn(i32) -> i32 = |x| x+2;
+/// let fnptr_addr = fnptr as usize;
+/// ```
+///
+/// However, a direct cast back is not possible. You need to use `transmute`:
+///
+/// ```rust
+/// # let fnptr: fn(i32) -> i32 = |x| x+2;
+/// # let fnptr_addr = fnptr as usize;
+/// let fnptr = fnptr_addr as *const ();
+/// let fnptr: fn(i32) -> i32 = unsafe { std::mem::transmute(fnptr) };
+/// assert_eq!(fnptr(40), 42);
+/// ```
+///
+/// Crucially, we `as`-cast to a raw pointer before `transmute`ing to a function pointer.
+/// This avoids an integer-to-pointer `transmute`, which can be problematic.
+/// Transmuting between raw pointers and function pointers (i.e., two pointer types) is fine.
+///
+/// Note that all of this is not portable to platforms where function pointers and data pointers
+/// have different sizes.
+///
/// ### Traits
///
/// Function pointers implement the following traits:
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