"Unavailable instance method... used to satisfy a requirement of protocol"

Using Swift
1

I am updating from Xcode 8 to Xcode 9, still using Swift 3.

In my project I am getting warnings of the pattern:

Unavailable instance method ‘compareQueryResult(_:toQueryResult:)’ was used to satisfy a requirement of protocol ‘ResultComparable’.

My project uses an Obj-C++ framework to wrap C++ and expose it in Obj-C.

The instance method in question is declared and implemented in a number of Obj-C classes in this framework.

@interface DocumentQuery: Query {
   - (ComparisonResult)compareQueryResult:(DocumentResult *)result1 toQueryResult:(DocumentResult *)result2;
}
@end

@interface GroupQuery: Query {
   - (ComparisonResult)compareQueryResult:(GroupResult *)result1 toQueryResult:(GroupResult *)result2;
}
@end

Another framework imports the Obj-C++ framework. In this framework the protocol is defined in Swift with an associated type:

public protocol ResultComparable
{
    associatedtype ResultType
    func compareQueryResult(_ r1: ResultType, toQueryResult r2: ResultType) -> ComparisonResult
}

And conformance is declared:

extension DocumentQuery: ResultComparable {}
extension GroupQuery: ResultComparable {}

This compiled without warnings in Xcode 8 / Swift 3, but they appear in Xcode 9 / Swift 3. Any help in understanding the issue and how to fix it would be greatly appreciated.

James

2

Hi, James. The trick here is that the name you’ll get in Swift for these methods is probably 'compareQuery(_:toQuery:)', because the Swift compiler detects that the “result” is redundant with the type name. In Xcode 8 the compiler didn’t check if you were using the “old" name to satisfy a protocol, but Xcode 9 now does (for unrelated reasons).

Since this is a source-breaking change, can you file an issue at https://bugs.swift.org <Issues · apple/swift · GitHub; ? At the very least we should make the diagnostic better.

You can always tell the Swift compiler you know better by using the NS_SWIFT_NAME annotation to provide an alternate name, using Swift function name syntax.

Jordan

···

On Sep 15, 2017, at 12:45, James Dempsey via swift-users <swift-users@swift.org> wrote:

I am updating from Xcode 8 to Xcode 9, still using Swift 3.

In my project I am getting warnings of the pattern:

Unavailable instance method ‘compareQueryResult(_:toQueryResult:)’ was used to satisfy a requirement of protocol ‘ResultComparable’.

My project uses an Obj-C++ framework to wrap C++ and expose it in Obj-C.

The instance method in question is declared and implemented in a number of Obj-C classes in this framework.

@interface DocumentQuery: Query {
   - (ComparisonResult)compareQueryResult:(DocumentResult *)result1 toQueryResult:(DocumentResult *)result2;
}
@end

@interface GroupQuery: Query {
   - (ComparisonResult)compareQueryResult:(GroupResult *)result1 toQueryResult:(GroupResult *)result2;
}
@end

Another framework imports the Obj-C++ framework. In this framework the protocol is defined in Swift with an associated type:

public protocol ResultComparable
{
    associatedtype ResultType
    func compareQueryResult(_ r1: ResultType, toQueryResult r2: ResultType) -> ComparisonResult
}

And conformance is declared:

extension DocumentQuery: ResultComparable {}
extension GroupQuery: ResultComparable {}

This compiled without warnings in Xcode 8 / Swift 3, but they appear in Xcode 9 / Swift 3. Any help in understanding the issue and how to fix it would be greatly appreciated.

James

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

3

Thanks Jordan!

I can definitely file an issue.

A better diagnostic would definitely help.

James

···

On Sep 15, 2017, at 2:03 PM, Jordan Rose <jordan_rose@apple.com> wrote:

Hi, James. The trick here is that the name you’ll get in Swift for these methods is probably 'compareQuery(_:toQuery:)', because the Swift compiler detects that the “result” is redundant with the type name. In Xcode 8 the compiler didn’t check if you were using the “old" name to satisfy a protocol, but Xcode 9 now does (for unrelated reasons).

Since this is a source-breaking change, can you file an issue at https://bugs.swift.org <Issues · apple/swift · GitHub; ? At the very least we should make the diagnostic better.

You can always tell the Swift compiler you know better by using the NS_SWIFT_NAME annotation to provide an alternate name, using Swift function name syntax.

Jordan

On Sep 15, 2017, at 12:45, James Dempsey via swift-users <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:

I am updating from Xcode 8 to Xcode 9, still using Swift 3.

In my project I am getting warnings of the pattern:

Unavailable instance method ‘compareQueryResult(_:toQueryResult:)’ was used to satisfy a requirement of protocol ‘ResultComparable’.

My project uses an Obj-C++ framework to wrap C++ and expose it in Obj-C.

The instance method in question is declared and implemented in a number of Obj-C classes in this framework.

@interface DocumentQuery: Query {
   - (ComparisonResult)compareQueryResult:(DocumentResult *)result1 toQueryResult:(DocumentResult *)result2;
}
@end

@interface GroupQuery: Query {
   - (ComparisonResult)compareQueryResult:(GroupResult *)result1 toQueryResult:(GroupResult *)result2;
}
@end

Another framework imports the Obj-C++ framework. In this framework the protocol is defined in Swift with an associated type:

public protocol ResultComparable
{
    associatedtype ResultType
    func compareQueryResult(_ r1: ResultType, toQueryResult r2: ResultType) -> ComparisonResult
}

And conformance is declared:

extension DocumentQuery: ResultComparable {}
extension GroupQuery: ResultComparable {}

This compiled without warnings in Xcode 8 / Swift 3, but they appear in Xcode 9 / Swift 3. Any help in understanding the issue and how to fix it would be greatly appreciated.

James

_______________________________________________
swift-users mailing list
swift-users@swift.org <mailto:swift-users@swift.org>
https://lists.swift.org/mailman/listinfo/swift-users