Why StringProtocol.hasSuffix has argument `prefix`?

ensan-hcl · 2021-05-08T08:03:03.957Z

apple/swift/blob/main/stdlib/public/core/StringProtocol.swift#L46


      
          where UnicodeScalarView.Element == Unicode.Scalar,
                UnicodeScalarView.Index == Index
          
          
associatedtype SubSequence = Substring
          
          
var utf8: UTF8View { get }
          var utf16: UTF16View { get }
          var unicodeScalars: UnicodeScalarView { get }
          
          
func hasPrefix(_ prefix: String) -> Bool
          func hasSuffix(_ suffix: String) -> Bool
          
          
func lowercased() -> String
          func uppercased() -> String
          
          
/// Creates a string from the given Unicode code units in the specified
          /// encoding.
          ///
          /// - Parameters:
          ///   - codeUnits: A collection of code units encoded in the encoding
          ///     specified in `sourceEncoding`.

Why this protocol required method hasPrefix has argument prefix not suffix?

Because its default implementation's argument name is suffix, when I use this method with value of type String, it appears hasPrefix(_ suffix: String).

image938×302 48.8 KB

However, when I use value of type some StringProtocol, it's argument name is prefix because protocol requirement uses prefix.

image968×230 39.9 KB

Is there any reason? Or simply it is mistake of implementation?

eskimo · 2021-05-08T09:58:46.634Z

Or simply it is mistake of implementation?

Yeah, that looks like a copy’n’paste bug, and I recommend that you file it as such. Please post your bug number, just for the record.

Well spotted btw!

Share and Enjoy

Quinn “The Eskimo!” @ DTS @ Apple

ensan-hcl · 2021-05-08T10:03:01.089Z

Thank you!

I created a PR about this a while back, but I didn't file this. Should I assign it myself?

github.com/apple/swift

Change the name of the hasSuffix argument of the StringProtocol requirement to `suffix` from `prefix`.

apple:main ← ensan-hcl:rename_hasSuffix

opened 08:27AM - 08 May 21 UTC

ensan-hcl

+1 -1

[SR-14611](https://bugs.swift.org/browse/SR-14611) https://github.com/apple…/swift/blob/7f4a1d5e20b4f43192d2cee9dd40a6869dba7f82/stdlib/public/core/StringProtocol.swift#L46 The argument of `hasSuffix` that `StringProtocol` requires is currently wrongly named. This PR replaces its name into `suffix` from `prefix`. Because the argument is labeled as `_`, this is an internal change. It wouldn't affect anywhere. I posted a question on the [forum](https://forums.swift.org/t/why-stringprotocol-hassuffix-has-argument-prefix/47976) just in case. I'm sorry if there is some purpose to name that `prefix`.

[EDIT] I did it.

github.com/apple/swift

[SR-14611] The argument of hasSuffix that StringProtocol requires is currently wrongly named

opened 12:27PM - 08 May 21 UTC

closed 07:12AM - 09 May 21 UTC

swift-ci

bug Standard Library

| | | |------------------|-----------------|… |Previous ID | SR-14611 | |Radar | None | |Original Reporter | ensan (JIRA User) | |Type | Bug | |Status | Closed | |Resolution | Done | <details> <summary>Environment</summary> Apple Swift version 5.4 (swiftlang-1205.0.26.9 clang-1205.0.19.55) Target: x86_64-apple-darwin20.3.0 </details> <details> <summary>Additional Detail from JIRA</summary> | | | |------------------|-----------------| |Votes | 0 | |Component/s | Standard Library | |Labels | Bug | |Assignee | ensan (JIRA) | |Priority | Medium | md5: 6ee0dc96ce528d7b90a1423b9e29abc7 </details> **Issue Description:** The argument of hasSuffix that StringProtocol requires is currently wrongly named. It should be \`suffix\`. <https://github.com/apple/swift/blob/main/stdlib/public/core/StringProtocol.swift#L46>