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

6fbd643

The OS/Variant where this issue occurs.

• iOS
• 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?

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

Additional Context

No response