std: Stabilize APIs for the 1.11.0 release

[alexcrichton]

Although the set of APIs being stabilized this release is relatively small, the
trains keep going! Listed below are the APIs in the standard library which have
either transitioned from unstable to stable or those from unstable to
deprecated.

Stable

• BTreeMap::{append, split_off}
• BTreeSet::{append, split_off}
• Cell::get_mut
• RefCell::get_mut
• BinaryHeap::append
• {f32, f64}::{to_degrees, to_radians} - libcore stabilizations mirroring past
  libstd stabilizations
• Iterator::sum
• Iterator::product

Deprecated

• {f32, f64}::next_after
• {f32, f64}::integer_decode
• {f32, f64}::ldexp
• {f32, f64}::frexp
• num::One
• num::Zero

Added APIs (all unstable)

• iter::Sum
• iter::Product
• iter::Step - a few methods were added to accomodate deprecation of One/Zero

Removed APIs

• From<Range<T>> for RangeInclusive<T> - everything about RangeInclusive is
  unstable

Closes #27739
Closes #27752
Closes #32526
Closes #33444
Closes #34152
cc #34529 (new tracking issue)

[rust-highfive]

r? @aturon

(rust_highfive has picked a reviewer for you, use r? to override)

[alexcrichton]

cc @rust-lang/libs, the deprecation of Zero and One had some particularly nasty fallout, but not totally unreasonable. The Step trait is getting farther and farther away from stabilization though in the implementation of iteration for a few range types.

[brson]

@alexcrichton Your comments about the fallout and unlikelihood of stabilizing Step are worrying. Are we digging ourselves into a hole with these unstable traits that stable APIs depend on? Are you still confident about stabilizing sum/product (sorry to keep harping on this)?

[alexcrichton]

I'm personally still confident in stabilizing the sum/product methods, but yes we're digging ourselves into a hole with Step and the various iterator implementations it's used for. I believe step_by is still unstable but it's used for the iterators on Range and RangeFrom, which are indeed stable.

The methods of Step used by the stable impl blocks are very small and minor (one could easily see stabilizing that triat). So I'm not as un-confident now that I read into it.

This would entail killing step_by and rethinking RangeInclusive iteration, however.

[SimonSapin]

Why always check rather than use + with its configurable behavior?

[alexcrichton]

With MIR we unfortunately don't have that luxury as whether the arithmetic is checked or not is encoded into the MIR, not generated at trans time.

[SimonSapin]

Is that relevant because libcore is usually distributed pre-compiled? If so it’s worth a source comment at least, and maybe a doc-comment.

[alexcrichton]

The overflow behavior is documented on the sum/product methods, and yes this is due to it being distributed as a compiled artifact.

[aturon]

One stability nit, otherwise r=me

[alexcrichton]

@bors: r=aturon

[bors]

📌 Commit 71dec1b has been approved by aturon

[bors]

⌛ Testing commit 71dec1b with merge 9ef8ff8...

[bors]

💔 Test failed - auto-win-gnu-32-opt-rustbuild

[arielb1]

> C:\bot\slave\auto-win-gnu-32-opt-rustbuild\build\src\libcore\iter\range.rs:207:17: 207:26 error: comparison is useless due to type limits
> C:\bot\slave\auto-win-gnu-32-opt-rustbuild\build\src\libcore\iter\range.rs:207                 *self < 0
> C:\bot\slave\auto-win-gnu-32-opt-rustbuild\build\src\libcore\iter\range.rs:247:1: 247:32 note: in this expansion of step_impl_no_between! (defined in C:\bot\slave\auto-win-gnu-32-opt-rustbuild\build\src\libcore\iter\range.rs)
> C:\bot\slave\auto-win-gnu-32-opt-rustbuild\build\src\libcore\lib.rs:60:31: 60:39 note: lint level defined here
> C:\bot\slave\auto-win-gnu-32-opt-rustbuild\build\src\libcore\lib.rs:60 #![cfg_attr(not(stage0), deny(warnings))]

[alexcrichton]

@bors: r=aturon

[bors]

📌 Commit 7cfcb4a has been approved by aturon

[bors]

⌛ Testing commit 7cfcb4a with merge f632159...

[bors]

💔 Test failed - auto-win-msvc-64-cargotest

[arielb1]

C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\num/f32.rs:114:26: 114:36 error: use of deprecated item: never really came to fruition and easily implementable outside the standard library
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\num/f32.rs:114             let (a, b) = f64::frexp(x as f64);
                                                                                                 ^~~~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289:31: 289:39 note: lint level defined here
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289 #![cfg_attr(not(stage0), deny(warnings))]
                                                                                                  ^~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\num/f32.rs:121:13: 121:23 error: use of deprecated item: never really came to fruition and easily implementable outside the standard library
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\num/f32.rs:121             f64::ldexp(x as f64, n as isize) as c_float
                                                                                    ^~~~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289:31: 289:39 note: lint level defined here
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289 #![cfg_attr(not(stage0), deny(warnings))]
                                                                                                  ^~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\sys/windows/mod.rs:17:5: 17:14 error: use of deprecated item: no longer used for Iterator::sum
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\sys/windows/mod.rs:17 use num::Zero;
                                                                                   ^~~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289:31: 289:39 note: lint level defined here
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289 #![cfg_attr(not(stage0), deny(warnings))]
                                                                                                  ^~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\sys/windows\net.rs:20:5: 20:13 error: unused import
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\sys/windows\net.rs:20 use ops::Neg;
                                                                                   ^~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289:31: 289:39 note: lint level defined here
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289 #![cfg_attr(not(stage0), deny(warnings))]
                                                                                                  ^~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\sys/windows/mod.rs:181:23: 181:27 error: use of deprecated item: no longer used for Iterator::sum
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\sys/windows/mod.rs:181 fn cvt<I: PartialEq + Zero>(i: I) -> io::Result<I> {
                                                                                                      ^~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289:31: 289:39 note: lint level defined here
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289 #![cfg_attr(not(stage0), deny(warnings))]
                                                                                                  ^~~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\sys/windows/mod.rs:182:13: 182:20 error: use of deprecated item: no longer used for Iterator::sum
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\sys/windows/mod.rs:182     if i == I::zero() {
                                                                                            ^~~~~~~
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289:31: 289:39 note: lint level defined here
C:\bot\slave\auto-win-msvc-64-cargotest\build\src\libstd\lib.rs:289 #![cfg_attr(not(stage0), deny(warnings))]

[alexcrichton]

@bors: r=aturon

[bors]

📌 Commit 3016626 has been approved by aturon

[bors]

⌛ Testing commit 3016626 with merge 696b703...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-mir, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-mir, auto-win-msvc-64-opt-rustbuild