Empty dictionaries of certain types throw an error when decoding

[mkeiser]

Expected Behavior

Some empty dictionaries that have been encoded with CBOREncoder throw a type mismatch error when the data is decoded again with CBORDecoder. To me this seems like a relatively severe bug.

Actual Behavior

See provided test methods.

Steps To Reproduce

Test methods I added to CBORDecoderTests. The first one currently fails, the second one succeeds.

    /// Fails!
    func testEmptyDictionaryRoundTripUInt64Key() throws {
        let dict = [UInt64: String]()
        let data = try CBOREncoder().encode(dict)
        let dict2: [UInt64: String] = try CBORDecoder().decode(from: data)
        XCTAssertEqual(dict, dict2)
    }

    /// Succeeds
    func testEmptyDictionaryRoundTripIntKey() throws {
        let dict = [Int: String]()
        let data = try CBOREncoder().encode(dict)
        let dict2: [Int: String] = try CBORDecoder().decode(from: data)
        XCTAssertEqual(dict, dict2)
    }

Other types fail too, for example dictionaries with Int32 keys.

Project Version

6fbd643c64cf6ef7a98391820c372d05fa9ed9ab

The OS/Variant where this issue occurs.

• [ ] iOS
• [X] macOS
• [ ] tvOS
• [ ] watchOS
• [ ] Mac Catalyst
• [ ] Other (Please specify in "Additional Context" section)

The version of Xcode that was used when this issue appeared.

15.0.1 (15A507)

What was the environment in which the issue appeared?

• [X] CBORCoding.xcodeproj
• [X] Package.swift
• [ ] Carthage
• [ ] CocoaPods
• [ ] Swift Package Manager
• [ ] Other (Please specify in "Additional Context" section)

Additional Context

No response