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added Linux compatibility #132

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added Linux compatibility #132

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33f406a
added Linux compatibility
codeOfRobin Nov 19, 2016
d4fc6ae
Merge pull request #1 from Anviking/master
Dec 13, 2016
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37 changes: 18 additions & 19 deletions Sources/DecodingError.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -9,52 +9,52 @@
import Foundation

public enum DecodingError: Error, Equatable {

/// `DecodingError.Metadata` provides information about
/// where an `DecodingError` was thrown in the JSON
/// where an `DecodingError` was thrown in the JSON
/// object graph.
public struct Metadata: Equatable {

public init(path: [String] = [], object: Any, rootObject: Any? = nil) {
self.path = path
self.object = object
self.rootObject = rootObject
}

/// The JSON key path to the object that failed to be decoded
public var path: [String]

/// The JSON object that failed to be decoded
public let object: Any

/// The root JSON object for which the `path` can be used to find `object`
public var rootObject: Any?

/// Represents the path to the object that failed decoding with "." as a separator.
public var formattedPath: String {
return path.joined(separator: ".")
}
}

/// Thrown when optional casting from `Any` fails.
///
/// This can happen both when trying to access a key on a object
/// that isn't a `NSDictionary`, and failing to cast a `Castable`
/// primitive.
case typeMismatch(expected: Any.Type, actual: Any.Type, Metadata)

/// Thrown when a given, required, key was not found in a dictionary.
case missingKey(String, Metadata)

/// Thrown from the `RawRepresentable` extension when
/// `init(rawValue:)` returned `nil`.
case rawRepresentableInitializationError(rawValue: Any, Metadata)
/// When an error is thrown that isn't `DecodingError`, it

/// When an error is thrown that isn't `DecodingError`, it
/// will be wrapped in `DecodingError.other` in order to also provide
/// metadata about where the error was thrown.
case other(Error, Metadata)

public var metadata: Metadata {
get {
switch self {
Expand All @@ -68,7 +68,7 @@ public enum DecodingError: Error, Equatable {
return metadata
}
}

set {
switch self {
case let .typeMismatch(expected, actual, _):
Expand All @@ -83,7 +83,7 @@ public enum DecodingError: Error, Equatable {
}

}

public var debugDescription: String {
switch self {
case let .typeMismatch(expected, actual, metadata):
Expand All @@ -96,7 +96,7 @@ public enum DecodingError: Error, Equatable {
return "\(error)"
}
}

}


Expand All @@ -110,9 +110,9 @@ public func ~=<T>(lhs: T.Type, rhs: Any.Type) -> Bool {

// FIXME: I'm not sure about === equality
public func ==(lhs: DecodingError.Metadata, rhs: DecodingError.Metadata) -> Bool {
return lhs.object as AnyObject === rhs.object as AnyObject
return lhs.object as? AnyObject === rhs.object as? AnyObject
&& lhs.path == rhs.path
&& lhs.rootObject as AnyObject === rhs.rootObject as AnyObject
&& lhs.rootObject as? AnyObject === rhs.rootObject as? AnyObject
}

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Looking at this change, the problem I see with it is if the cast to AnyObject fails for both sides, then the operator will return true even though they may be different objects.

I'm not sure, but with Swift 3, is it possible to use as Any instead?

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Well, AnyObject is supposed to represent reference types. Technically, since DecodingError.Metadata(both lhs and rhs is a struct, this should fail 🤔. Can you confirm @Anviking ?

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Also, of note, this comment

// FIXME: I'm not sure about === equality
We may be right about this 😅

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Yeah, ok, so looking at this, the objects in the meta are Any, so this is trying to convert to a ref type so it can compare pointers (the === operator). I think. This may also be a holdover from the swift 2.x codebase that is no longer necessary.

I'll check to see if we can use === on Any in swift 3.

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Ok, confirmed. One cannot use === on Any

We're going to have to think up a different bit of logic to make this right.

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The only real problem with the as? is that it generates a warning: "Any to AnyObject always succeeds"

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@codeOfRobin codeOfRobin Nov 20, 2016 •
edited
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The only real problem with the as? is that it generates a warning: "Any to AnyObject always succeeds"

When you think about it, this shouldn't be true. What happens when you cast a struct to AnyObject ?

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@Anviking Anviking Nov 20, 2016 •
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When you think about it, this shouldn't be true. What happens when you cast a struct to AnyObject ?

On linux, no, on macOS and iOS, yes:

 28> struct A {}
 29> let a = A()
a: A = {}
error: could not fetch result -- error: Couldn't apply expression side effects : Couldn't dematerialize a: corresponding symbol wasn't found

 30> a as AnyObject
$R2: AnyObject = {
  instance_type = 0x0000000101001220
}

This looks like a swift language bug/inconsistency to me. If nothing else, we could use #if os to limit warnings to linux.

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Yeah, I think using if OS and adding an issue on https://github.com/apple/swift should be good enough for now.

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I think this is it
https://bugs.swift.org/browse/SR-2287?jql=text%20~%20%22linux%20anyobject%20cast%22

public func ==(lhs: DecodingError, rhs: DecodingError) -> Bool {
Expand Down Expand Up @@ -140,4 +140,3 @@ public func ==(lhs: DecodingError, rhs: DecodingError) -> Bool {
return false
}
}