Document panic in RangeInclusive::from(legacy::RangeInclusive)

[tbu-]

No description provided.

[rustbot]

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[jhpratt]

Has this been approved by T-libs-api? The panic message clearly says unspecified, so adding this documentation would overrule that.

[tbu-]

If T-libs doesn't want to guarantee this, I can change the wording to "currently panics, may not panic in the future". Or even "may panic".

[fmease]

#155394

[rust-log-analyzer]

The job pr-check-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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---- library/core/src/range.rs - range::RangeInclusive<T>::from (line 413) stdout ----
error[E0658]: use of unstable library feature `new_range_api_legacy`
   --> library/core/src/range.rs:418:13
    |
418 | let single: legacy::RangeInclusive<i32> = 0..=1;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #125687 <https://github.com/rust-lang/rust/issues/125687> for more information
    = help: add `#![feature(new_range_api_legacy)]` to the crate attributes to enable
    = note: this compiler was built on 2026-04-17; consider upgrading it if it is out of date

error[E0658]: use of unstable library feature `new_range_api_legacy`
   --> library/core/src/range.rs:422:12
    |
422 | let empty: legacy::RangeInclusive<i32> = 0..=0;
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #125687 <https://github.com/rust-lang/rust/issues/125687> for more information
    = help: add `#![feature(new_range_api_legacy)]` to the crate attributes to enable
    = note: this compiler was built on 2026-04-17; consider upgrading it if it is out of date

error[E0609]: no field `end` on type `std::range::RangeInclusive<i32>`
   --> library/core/src/range.rs:420:34
    |
420 | assert_eq!((single.start, single.end), (0, 1));
    |                                  ^^^ unknown field
    |
    = note: available fields are: `start`, `last`

error[E0609]: no field `end` on type `std::range::RangeInclusive<i32>`
   --> library/core/src/range.rs:424:32
    |
424 | assert_eq!((empty.start, empty.end), (0, 0));
    |                                ^^^ unknown field
    |
    = note: available fields are: `start`, `last`

error: aborting due to 4 previous errors
---
---- library/core/src/range.rs - range::RangeInclusive<T>::from (line 426) stdout ----
error[E0658]: use of unstable library feature `new_range_api_legacy`
   --> library/core/src/range.rs:431:20
    |
431 | let mut exhausted: legacy::RangeInclusive<i32> = 0..=0;
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #125687 <https://github.com/rust-lang/rust/issues/125687> for more information
    = help: add `#![feature(new_range_api_legacy)]` to the crate attributes to enable
    = note: this compiler was built on 2026-04-17; consider upgrading it if it is out of date