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[SR-4664] Bad diagnostic passing incorrect type to method in generic type #47241

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NachoSoto opened this issue Apr 21, 2017 · 4 comments
Closed

[SR-4664] Bad diagnostic passing incorrect type to method in generic type #47241

NachoSoto opened this issue Apr 21, 2017 · 4 comments
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 type checker Area → compiler: Semantic analysis

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@NachoSoto
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Previous ID SR-4664
Radar rdar://problem/31764828
Original Reporter @NachoSoto
Type Bug
Status Resolved
Resolution Done
Environment

Apple Swift version 3.1 (swiftlang-802.0.53 clang-802.0.42)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, DiagnosticsQoI, TypeChecker
Assignee None
Priority Medium

md5: c0118e87c48248a5048d979e49a82d3c

Issue Description:

This code:

struct M<T> where T : Collection {
    static func f(a: T, b: T) -> [E<T.Iterator.Element>] {
    
    }
}

enum E<T> {}

struct S {}

struct X {
    struct Y {
        let s: [S]
    }

    let y: [Y]
}

let x = X(y: [])

let a = M.f(a: x.y[0], b: x.y[1])

Produces:

error: repl.swift:26:19: error: ambiguous reference to member 'subscript'
let a = M.f(a: x.y[0], b: x.y[1])
               ~~~^~~

Swift.Array:402:12: note: found this candidate
    public subscript(index: Int) -> Element { get set }
           ^

Swift.Array:429:12: note: found this candidate
    public subscript(bounds: Range<Int>) -> ArraySlice<Element> { get set }
           ^

Swift.RangeReplaceableCollection:2:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> RangeReplaceableSlice<Self> { get }
           ^

Swift.RangeReplaceableCollection:2:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> MutableRangeReplaceableSlice<Self> { get set }
           ^

Swift.RangeReplaceableCollection:2:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> RangeReplaceableBidirectionalSlice<Self> { get }
           ^

Swift.RangeReplaceableCollection:2:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> MutableRangeReplaceableBidirectionalSlice<Self> { get set }
           ^

Swift.RangeReplaceableCollection:2:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> RangeReplaceableRandomAccessSlice<Self> { get }
           ^

Swift.RangeReplaceableCollection:2:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> MutableRangeReplaceableRandomAccessSlice<Self> { get set }
           ^

Swift.RandomAccessCollection:26:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> RandomAccessSlice<Self> { get }
           ^

Swift.BidirectionalCollection:5:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> BidirectionalSlice<Self> { get }
           ^

Swift._MutableIndexable:24:12: note: found this candidate
    public subscript(bounds: ClosedRange<Self.Index>) -> Self.SubSequence { get set }
           ^

Swift._MutableIndexable:24:12: note: found this candidate
    public subscript(bounds: CountableRange<Self.Index>) -> Self.SubSequence { get set }
           ^

Swift._MutableIndexable:47:12: note: found this candidate
    public subscript(bounds: CountableClosedRange<Self.Index>) -> Self.SubSequence { get set }
           ^

Swift._Indexable:23:12: note: found this candidate
    public subscript(bounds: ClosedRange<Self.Index>) -> Self.SubSequence { get }
           ^

Swift._Indexable:23:12: note: found this candidate
    public subscript(bounds: CountableRange<Self.Index>) -> Self.SubSequence { get }
           ^

Swift._Indexable:45:12: note: found this candidate
    public subscript(bounds: CountableClosedRange<Self.Index>) -> Self.SubSequence { get }
           ^

Swift.Collection:27:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> Slice<Self> { get }
           ^

Swift.MutableCollection:25:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> MutableSlice<Self> { get set }
           ^

Swift.MutableCollection:2:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> MutableBidirectionalSlice<Self> { get set }
           ^

Swift.MutableCollection:2:12: note: found this candidate
    public subscript(bounds: Range<Self.Index>) -> MutableRandomAccessSlice<Self> { get set }
           ^

Instead of telling me something more useful, like the fact that `x.y[index]` is type `Y`, which doesn't conform to `Collection`.
@jckarter
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@swift-ci create

@NachoSoto
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Wow, surprised! This is fixed in Swift 4.0. I'm gonna leave it open to make sure that you guys add regression tests for this.

@slavapestov
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I updated the radar with a note to add a regression test.

@NachoSoto
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Thanks @slavapestov!

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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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 type checker Area → compiler: Semantic analysis
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@slavapestov @jckarter @NachoSoto