std: Add AsRef/AsMut impls to Box/Rc/Arc #28811
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These common traits were left off originally by accident from these smart pointers, and a past attempt (rust-lang#26008) to add them was later reverted (rust-lang#26160) due to unexpected breakge (rust-lang#26096) occurring. The specific breakage in worry is the meaning of this return value changed: let a: Box<Option<T>> = ...; a.as_ref() Currently this returns `Option<&T>` but after this change it will return `&Option<T>` because the `AsRef::as_ref` method shares the same name as `Option::as_ref`. A [crater report][crater] of this change, however, has shown that the fallout of this change is quite minimal. These trait implementations are "the right impls to add" to these smart pointers and would enable various generalizations such as those in rust-lang#27197. [crater]: https://gist.github.com/anonymous/0ba4c3512b07641c0f99 This commit is a breaking change for the above reasons mentioned, and the mitigation strategies look like any of: Option::as_ref(&a) a.as_ref().as_ref() (*a).as_ref()
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r? @aturon (rust_highfive has picked a reviewer for you, use r? to override) |
alexcrichton
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T-libs-api
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Of the breakage in the crater report, it was also decided that if we move forward with this that we'll send a PR to cairo to get ahead of the breakage there. |
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@bors: r+ |
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📌 Commit db76ac7 has been approved by |
bors
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Oct 8, 2015
These common traits were left off originally by accident from these smart pointers, and a past attempt (#26008) to add them was later reverted (#26160) due to unexpected breakge (#26096) occurring. The specific breakage in worry is the meaning of this return value changed: let a: Box<Option<T>> = ...; a.as_ref() Currently this returns `Option<&T>` but after this change it will return `&Option<T>` because the `AsRef::as_ref` method shares the same name as `Option::as_ref`. A [crater report][crater] of this change, however, has shown that the fallout of this change is quite minimal. These trait implementations are "the right impls to add" to these smart pointers and would enable various generalizations such as those in #27197. [crater]: https://gist.github.com/anonymous/0ba4c3512b07641c0f99 This commit is a breaking change for the above reasons mentioned, and the mitigation strategies look like any of: Option::as_ref(&a) a.as_ref().as_ref() (*a).as_ref()
This was referenced Oct 16, 2015
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These common traits were left off originally by accident from these smart
pointers, and a past attempt (#26008) to add them was later reverted (#26160)
due to unexpected breakge (#26096) occurring. The specific breakage in worry is
the meaning of this return value changed:
Currently this returns
Option<&T>but after this change it will return&Option<T>because theAsRef::as_refmethod shares the same name asOption::as_ref. A crater report of this change, however, has shownthat the fallout of this change is quite minimal. These trait implementations
are "the right impls to add" to these smart pointers and would enable various
generalizations such as those in #27197.
This commit is a breaking change for the above reasons mentioned, and the
mitigation strategies look like any of: