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[SR-6118] mechanism to hand through #file/#line in subscripts #48673

weissi opened this issue Oct 11, 2017 · 4 comments

[SR-6118] mechanism to hand through #file/#line in subscripts #48673

weissi opened this issue Oct 11, 2017 · 4 comments


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weissi commented Oct 11, 2017

Previous ID SR-6118
Radar None
Original Reporter @weissi
Type New Feature
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels New Feature
Assignee @slavapestov
Priority Medium

md5: b802d9f73456058327d450079e18b6e4

Issue Description:

For my hypothetical MyArray implementation, in normal functions I can write

function get(index: Int, file: StaticString = #file, line: UInt = #line) -> Value {
    if !checkIndex(index) {
        fatalError("index \(index) out of bound", file: file, line: line)

and I'll be able to create good error messages for the user.

In subscripts however, default arguments are disallowed so

subscript(index: Int) -> Value {
    if !checkIndex(index) {
        fatalError("index \(index) out of bound")

will always show its literal line and file rather than the callers.

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belkadan commented Oct 11, 2017

That should look like this:

struct A {
  subscript(a: Int, file: String = #file) -> Int {
    return a


but we don't allow default arguments in subscripts at the moment (because it's unclear how they would work with inout subscripts).

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Member Author

weissi commented Nov 16, 2017

@belkadan, sorry, could you expand on the inout subscripts? I don't know what they are 🙂

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slavapestov commented Apr 3, 2019


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swift-ci commented Jan 29, 2020

Comment by Joseph Twomey (JIRA)

@swift-ci create

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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