JSONDecoder Decimal Error

JSONDecoder-Decimal.swift

import Foundation

struct DoubleItem : Codable {
    var name: String
    var price: Double
}

struct DecimalItem : Codable {
    var name: String
    var price: Decimal
}

let jsonString = """
    { "name": "Gum ball", "price": 0.1 }
    """
let jsonData = jsonString.data(using: .utf8)!

let decoder = JSONDecoder()
do {
    let doubleItem = try decoder.decode(DoubleItem.self, from: jsonData)
    print(doubleItem)

    let decimalItem = try decoder.decode(DecimalItem.self, from: jsonData)
    print(decimalItem)
} catch {
    print(error)
}

// Output Xcode 9b3:
//    DoubleItem(name: "Gum ball", price: 0.10000000000000001)
//    typeMismatch(Swift.Dictionary<Swift.String, Any>, Swift.DecodingError.Context(codingPath: [Optional(__lldb_expr_5.DecimalItem.(CodingKeys in _AEF227D1F6EED9315B49119185CDD264).price)], debugDescription: "Expected to decode Dictionary<String, Any> but found a number instead."))

// Output Xcode 9b4:
//    DoubleItem(name: "Gum ball", price: 0.10000000000000001)
//    DecimalItem(name: "Gum ball", price: 0.1)

// Output Xcode 9.2 (9C40b):
// DoubleItem(name: "Gum ball", price: 0.10000000000000001)
// DecimalItem(name: "Gum ball", price: 0.1)

But if price = 9.37, the error would still be there:
// DoubleItem(name: "Gum ball", price: 9.3699999999999992)
// DecimalItem(name: "Gum ball", price: 9.369999999999997952)

// Output Xcode 9.2 (9C40b):
// Apple Swift version 4.0.3 (swiftlang-900.0.74.1 clang-900.0.39.2)
//{ "name": "Gum ball", "price": 46.984765 }
DoubleItem(name: "Gum ball", price: 46.984765000000003)
DecimalItem(name: "Gum ball", price: 46.98476500000001024)

Same output with 4.1 swift-DEVELOPMENT-SNAPSHOT-2018-02-20-a-ubuntu16.04.
Is this a Swift / foundation bug or an intended behavior?