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Tracking issue for Unicode enforcement in std::fmt (RFC 526) #20352

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aturon opened this issue Dec 30, 2014 · 1 comment · Fixed by #20377
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Tracking issue for Unicode enforcement in std::fmt (RFC 526) #20352

aturon opened this issue Dec 30, 2014 · 1 comment · Fixed by #20377
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B-RFC-approved Blocker: Approved by a merged RFC but not yet implemented.

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aturon commented Dec 30, 2014

RFC
@aturon aturon added A-libs B-RFC-approved Blocker: Approved by a merged RFC but not yet implemented. labels Dec 30, 2014
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aturon commented Dec 30, 2014

cc @alexcrichton

@aturon aturon mentioned this issue Dec 30, 2014
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@alexcrichton alexcrichton mentioned this issue Dec 31, 2014
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alexcrichton added a commit to alexcrichton/rust that referenced this issue Jan 2, 2015
@alexcrichton
std: Enforce Unicode in fmt::Writer
e423fcf 
This commit is an implementation of [RFC 526][rfc] which is a change to alter
the definition of the old `fmt::FormatWriter`. The new trait, renamed to
`Writer`, now only exposes one method `write_str` in order to guarantee that all
implementations of the formatting traits can only produce valid Unicode.

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0526-fmt-text-writer.md

One of the primary improvements of this patch is the performance of the
`.to_string()` method by avoiding an almost-always redundant UTF-8 check. This
is a breaking change due to the renaming of the trait as well as the loss of the
`write` method, but migration paths should be relatively easy:

* All usage of `write` should move to `write_str`. If truly binary data was
  being written in an implementation of `Show`, then it will need to use a
  different trait or an altogether different code path.

* All usage of `write!` should continue to work as-is with no modifications.

* All usage of `Show` where implementations just delegate to another should
  continue to work as-is.

[breaking-change]

Closes rust-lang#20352
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std: Enforce Unicode in fmt::Writer alexcrichton/rust
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