[SR-11470] Swift ignores "unavailable" attribute of initializer declared in an ObjC protocol for a Swift subclass of ObjC class

[swift-ci]

Previous ID	SR-11470
Radar	rdar://problem/55401820
Original Reporter	westacular (JIRA User)
Type	Bug

Attachment: Download

Environment

Tested with identical results in both - Xcode 10.3 / Swift 5.0 - Xcode 11 GM / Swift 5.1

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Compiler | |Labels | Bug, ClangImporter | |Assignee | None | |Priority | Medium | md5: eafdeed1bca5c71df626c723596ac258

relates to:

• SR-6993 Swift imports @optional ObjC methods from superclass protocol as if implemented

Issue Description:

If you have

• a Swift subclass of an ObjC class

• where the ObjC class conforms to an ObjC protocol,

• the protocol declares an init method marked as unavailable,

• the ObjC class (correctly) does not implement the unavailable init method,

• and the Swift subclass declares its own init method

... the Swift compiler will incorrectly require that the unavailable init method be implemented in the Swift subclass.

This does not appear to be an issue for a Swift class conforming to the protocol directly, or a Swift subclass of a Swift class that conforms.

Example:

@protocol SomeObjcProtocol <NSObject>

- (instancetype)initWithFoo:(BOOL)foo __attribute__((unavailable("do not use initWithFoo")));

@end

@interface SomeObjcClass : NSObject <SomeObjcProtocol>

@end

with an empty implementation of SomeObjcClass, we see

class SomeSwiftSubclass: SomeObjcClass {

    init(bar: Bool) {
        super.init()
    }

    // Error: "'required' initializer 'init(foo:)' must be provided by subclass of 'SomeObjcClass'"
}

class AnotherSwiftClass: NSObject, SomeObjcProtocol {

    init(bar: Bool) {
        super.init()
    }

    // No error
}

class AnotherSwiftSubclass: AnotherSwiftClass {

    init(baz: Int) {
        super.init(bar: true)
    }

    // No error
}

Inserting the fixit of

    required init(foo: Bool) {
        fatalError("init(foo:) has not been implemented")
    }

allows SomeSwiftSubclass to build. (In fact, it builds without a warning, but that's a separate issue: [SR-2317])

[swift-ci]

Comment by Wes Campaigne (JIRA)

Possibly related: SR-6993?

[belkadan]

Yeah. This one's going to be tricky to deal with without breaking source compatibility.

@swift-ci create