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Rollup merge of rust-lang#80958 - bstrie:deptbdnums, r=KodrAus
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Deprecate-in-future the constants superceded by RFC 2700

Successor to rust-lang#78335, re-opened after addressing the issues tracked in rust-lang#68490.

This PR makes use of the new ability to explicitly annotate an item as triggering the deprecated-in-future lint (via `rustc_deprecated(since="TBD"`, see rust-lang#78381). We might call this *soft deprecation*; unlike with deprecation, users will *not* receive warnings when compiling code that uses these items *unless* they opt-in via `#[warn(deprecated_in_future)]`. Like deprecation, soft deprecation causes documentation to formally acknowledge that an item is marked for eventual deprecation (at a non-specific point in the future).

With this new ability, we can sidestep all debate about when or on what timeframe something ought to be deprecated; as long as we can agree that something ought to be deprecated, we can receive much of the benefits of deprecation with none of the drawbacks. For these items specifically, the libs team has already agreed that they should be deprecated (see rust-lang#68490 (comment)).
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@JohnTitor
JohnTitor committed Jan 14, 2021
2 parents 3e42020 + c0c607c commit 3a22854
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Showing 22 changed files with 241 additions and 90 deletions.
2 changes: 1 addition & 1 deletion library/core/src/iter/adapters/chain.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
use crate::iter::{DoubleEndedIterator, FusedIterator, Iterator, TrustedLen};
use crate::{ops::Try, usize};
use crate::ops::Try;

/// An iterator that links two iterators together, in a chain.
///
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64 changes: 60 additions & 4 deletions library/core/src/num/f32.rs
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Original file line number Diff line number Diff line change
@@ -1,12 +1,13 @@
//! This module provides constants which are specific to the implementation
//! of the `f32` floating point data type.
//! Constants specific to the `f32` single-precision floating point type.
//!
//! *[See also the `f32` primitive type](../../std/primitive.f32.html).*
//!
//! Mathematically significant numbers are provided in the `consts` sub-module.
//!
//! Although using these constants won’t cause compilation warnings,
//! new code should use the associated constants directly on the primitive type.
//! For the constants defined directly in this module
//! (as distinct from those defined in the `consts` sub-module),
//! new code should instead use the associated constants
//! defined directly on the `f32` type.

#![stable(feature = "rust1", since = "1.0.0")]

Expand All @@ -23,12 +24,14 @@ use crate::num::FpCategory;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let r = std::f32::RADIX;
///
/// // intended way
/// let r = f32::RADIX;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(since = "TBD", reason = "replaced by the `RADIX` associated constant on `f32`")]
pub const RADIX: u32 = f32::RADIX;

/// Number of significant digits in base 2.
Expand All @@ -38,12 +41,17 @@ pub const RADIX: u32 = f32::RADIX;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let d = std::f32::MANTISSA_DIGITS;
///
/// // intended way
/// let d = f32::MANTISSA_DIGITS;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `MANTISSA_DIGITS` associated constant on `f32`"
)]
pub const MANTISSA_DIGITS: u32 = f32::MANTISSA_DIGITS;

/// Approximate number of significant digits in base 10.
Expand All @@ -53,12 +61,14 @@ pub const MANTISSA_DIGITS: u32 = f32::MANTISSA_DIGITS;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let d = std::f32::DIGITS;
///
/// // intended way
/// let d = f32::DIGITS;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(since = "TBD", reason = "replaced by the `DIGITS` associated constant on `f32`")]
pub const DIGITS: u32 = f32::DIGITS;

/// [Machine epsilon] value for `f32`.
Expand All @@ -72,12 +82,17 @@ pub const DIGITS: u32 = f32::DIGITS;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let e = std::f32::EPSILON;
///
/// // intended way
/// let e = f32::EPSILON;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `EPSILON` associated constant on `f32`"
)]
pub const EPSILON: f32 = f32::EPSILON;

/// Smallest finite `f32` value.
Expand All @@ -87,12 +102,14 @@ pub const EPSILON: f32 = f32::EPSILON;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let min = std::f32::MIN;
///
/// // intended way
/// let min = f32::MIN;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(since = "TBD", reason = "replaced by the `MIN` associated constant on `f32`")]
pub const MIN: f32 = f32::MIN;

/// Smallest positive normal `f32` value.
Expand All @@ -102,12 +119,17 @@ pub const MIN: f32 = f32::MIN;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let min = std::f32::MIN_POSITIVE;
///
/// // intended way
/// let min = f32::MIN_POSITIVE;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `MIN_POSITIVE` associated constant on `f32`"
)]
pub const MIN_POSITIVE: f32 = f32::MIN_POSITIVE;

/// Largest finite `f32` value.
Expand All @@ -117,12 +139,14 @@ pub const MIN_POSITIVE: f32 = f32::MIN_POSITIVE;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let max = std::f32::MAX;
///
/// // intended way
/// let max = f32::MAX;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(since = "TBD", reason = "replaced by the `MAX` associated constant on `f32`")]
pub const MAX: f32 = f32::MAX;

/// One greater than the minimum possible normal power of 2 exponent.
Expand All @@ -132,12 +156,17 @@ pub const MAX: f32 = f32::MAX;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let min = std::f32::MIN_EXP;
///
/// // intended way
/// let min = f32::MIN_EXP;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `MIN_EXP` associated constant on `f32`"
)]
pub const MIN_EXP: i32 = f32::MIN_EXP;

/// Maximum possible power of 2 exponent.
Expand All @@ -147,12 +176,17 @@ pub const MIN_EXP: i32 = f32::MIN_EXP;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let max = std::f32::MAX_EXP;
///
/// // intended way
/// let max = f32::MAX_EXP;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `MAX_EXP` associated constant on `f32`"
)]
pub const MAX_EXP: i32 = f32::MAX_EXP;

/// Minimum possible normal power of 10 exponent.
Expand All @@ -162,12 +196,17 @@ pub const MAX_EXP: i32 = f32::MAX_EXP;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let min = std::f32::MIN_10_EXP;
///
/// // intended way
/// let min = f32::MIN_10_EXP;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `MIN_10_EXP` associated constant on `f32`"
)]
pub const MIN_10_EXP: i32 = f32::MIN_10_EXP;

/// Maximum possible power of 10 exponent.
Expand All @@ -177,12 +216,17 @@ pub const MIN_10_EXP: i32 = f32::MIN_10_EXP;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let max = std::f32::MAX_10_EXP;
///
/// // intended way
/// let max = f32::MAX_10_EXP;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `MAX_10_EXP` associated constant on `f32`"
)]
pub const MAX_10_EXP: i32 = f32::MAX_10_EXP;

/// Not a Number (NaN).
Expand All @@ -192,12 +236,14 @@ pub const MAX_10_EXP: i32 = f32::MAX_10_EXP;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let nan = std::f32::NAN;
///
/// // intended way
/// let nan = f32::NAN;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(since = "TBD", reason = "replaced by the `NAN` associated constant on `f32`")]
pub const NAN: f32 = f32::NAN;

/// Infinity (∞).
Expand All @@ -207,12 +253,17 @@ pub const NAN: f32 = f32::NAN;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let inf = std::f32::INFINITY;
///
/// // intended way
/// let inf = f32::INFINITY;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `INFINITY` associated constant on `f32`"
)]
pub const INFINITY: f32 = f32::INFINITY;

/// Negative infinity (−∞).
Expand All @@ -222,12 +273,17 @@ pub const INFINITY: f32 = f32::INFINITY;
///
/// ```rust
/// // deprecated way
/// # #[allow(deprecated, deprecated_in_future)]
/// let ninf = std::f32::NEG_INFINITY;
///
/// // intended way
/// let ninf = f32::NEG_INFINITY;
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(
since = "TBD",
reason = "replaced by the `NEG_INFINITY` associated constant on `f32`"
)]
pub const NEG_INFINITY: f32 = f32::NEG_INFINITY;

/// Basic mathematical constants.
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