[swift-evolution] [Review] SE-0128: Change failable UnicodeScalar initializers to failable

[王 黎明]

+0.

Maybe off topic.

The problem is there’s no process for the validty of the parameter.

The source of UnicodeScala:

  public init(_ v: UInt32) {
    // Unicode 6.3.0:
    //
    //     D9.  Unicode codespace: A range of integers from 0 to 10FFFF.
    //
    //     D76. Unicode scalar value: Any Unicode code point except
    //     high-surrogate and low-surrogate code points.
    //
    //     * As a result of this definition, the set of Unicode scalar values
    //     consists of the ranges 0 to D7FF and E000 to 10FFFF, inclusive.

    _precondition(v < 0xD800 || v > 0xDFFF,
        "high- and low-surrogate code points are not valid Unicode scalar values")
    _precondition(v <= 0x10FFFF, "value is outside of Unicode codespace")

    self._value = v
  }

55357 == 0xD83D , not less than 0xD800

The _precondition like assert.





在 2016年7月22日，上午10:23，Karl via swift-evolution <swift-evolution at swift.org<mailto:swift-evolution at swift.org>> 写道：

+1. I was trying to build a naive random string generator the other day (but I wanted it to occasionally spit out extended clusters like emojis), and was also surprised that the initialiser crashes.

Could probably be filed under “bug fixes”, even.

Karl

On 22 Jul 2016, at 00:28, Chris Lattner via swift-evolution <swift-evolution at swift.org<mailto:swift-evolution at swift.org>> wrote:

Hello Swift community,

The review of "SE-0128: Change failable UnicodeScalar initializers to failable" begins now and runs through July 24. The proposal is available here:

https://github.com/apple/swift-evolution/blob/master/proposals/0128-unicodescalar-failable-initializer.md

Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at

https://lists.swift.org/mailman/listinfo/swift-evolution

or, if you would like to keep your feedback private, directly to the review manager.

What goes into a review?

The goal of the review process is to improve the proposal under review through constructive criticism and contribute to the direction of Swift. When writing your review, here are some questions you might want to answer in your review:

* What is your evaluation of the proposal?
* Is the problem being addressed significant enough to warrant a change to Swift?
* Does this proposal fit well with the feel and direction of Swift?
* If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
* How much effort did you put into your review? A glance, a quick reading, or an in-depth study?

More information about the Swift evolution process is available at

https://github.com/apple/swift-evolution/blob/master/process.md

Thank you,

-Chris Lattner
Review Manager


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