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[SR-5688] Unhelpful diagnostic when missing a ? in a KeyPath expression #48258

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mdiep opened this issue Aug 15, 2017 · 6 comments
Closed

[SR-5688] Unhelpful diagnostic when missing a ? in a KeyPath expression #48258

mdiep opened this issue Aug 15, 2017 · 6 comments
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@LucianoPAlmeida
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation

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@mdiep
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mdiep commented Aug 15, 2017

Previous ID SR-5688
Radar None
Original Reporter @mdiep
Type Bug
Status Resolved
Resolution Done

Attachment: Download

Environment

Xcode 9.0.0 ß5

Apple Swift version 4.0 (swiftlang-900.0.59 clang-900.0.34.2)

Target: x86_64-apple-macosx10.9

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, DiagnosticsQoI
Assignee @LucianoPAlmeida
Priority Medium

md5: c71e85e71edfd0319c05a4dfe3d8443e

Issue Description:

This code:

struct A {
    var b: B?
}

struct B {
    var c: Int
}

let ab1 = \A.b.c
dump(ab1)

gives this diagnostic:

error: MyPlayground.playground:3:11: error: expression type 'WritableKeyPath<A, Int>' is ambiguous without more context
let ab1 = \A.b.c

That's really unhelpful. The issue here is that a ? is missing. It should be \A.b?.c.
@mdiep
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mdiep commented Aug 15, 2017

It's not clear to me that \A.b.c means anything, so I'm left wondering if KeyPaths should even use ?.

@belkadan
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cc @jckarter, @xedin

@LucianoPAlmeida
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On 2020-06-13 master snapshot I'm seeing

![](Screen Shot 2020-06-14 at 12.21.48.png)

@gregomni
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@LucianoPAlmeida - Sorry, I started looking at this because I hadn't noticed that you'd assigned it to yourself. The fix needs to deal with key path expressions specially to get the particular component involved. Something like this: <gregomni@b164ae8c7a30656d7b986aa1edfaf1f08b7c2f1c\>

@LucianoPAlmeida
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Ahh thank you, I had the PR opened right after the post, very similar except for the SourceLoc part, which I believe is an improvement. I'll adjust that and add you as a reviewer as well 🙂

@LucianoPAlmeida
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@mdiep This is fixed on master, can you please verify on the next available master snapshot and close? Thanks

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@LucianoPAlmeida LucianoPAlmeida

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation
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@mdiep @belkadan @LucianoPAlmeida @gregomni