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[SR-11453] Unhelpful error message when equating an optional enum that does not conform to Equatable #53854

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swift-ci opened this issue Sep 11, 2019 · 1 comment
Open

[SR-11453] Unhelpful error message when equating an optional enum that does not conform to Equatable #53854

swift-ci opened this issue Sep 11, 2019 · 1 comment
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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 type checker Area → compiler: Semantic analysis

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@swift-ci
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Previous ID SR-11453
Radar None
Original Reporter apaszke (JIRA User)
Type Bug
Environment

Apple Swift version 5.1 (swiftlang-1100.0.257.2 clang-1100.0.31.3)

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

md5: 8a3854ab7fb3ac4be15e8e76981b5840

Issue Description:

The following code is incorrect, because `E` does not explicitly declare a conformance to `Equatable`:

enum E {
    case a(Int)
    case b(String)
}

var lookup: [Int: E] = [:]
guard lookup[0] == .unknown else { fatalError() }

However, the error message emitted by `swiftc` is the following, which does not really help in finding the root cause:

error.swift:7:21: error: type 'E?' has no member 'unknown'
guard lookup[0] == .unknown else { fatalError() }
                   ~^~~~~~~
@belkadan
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cc @hborla, @xedin

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