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[SR-13515] Incorrect fix-it when attempting to extend an objc protocol with a default implementation #55951

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amomchilov opened this issue Sep 7, 2020 · 2 comments
Open

[SR-13515] Incorrect fix-it when attempting to extend an objc protocol with a default implementation #55951

amomchilov opened this issue Sep 7, 2020 · 2 comments
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@theblixguy
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation type checker Area → compiler: Semantic analysis

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@amomchilov
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Previous ID SR-13515
Radar rdar://problem/68476523
Original Reporter @amomchilov
Type Bug
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, DiagnosticsQoI, TypeChecker
Assignee @theblixguy
Priority Medium

md5: 1e0dc6ae6b02f489a3c7f3c42370108b

Issue Description:

@objc protocols don't support default implementations for methods via extensions. Attempting to do so makes the compiler suggest that you add the @objc attribute to your default method implementation, which instead it should tell you that the entire construct is invalid.

Example code:

import Foundation

@objc protocol ObjCProtocol {
    @objc func requiredMethod()
}

extension ObjCProtocol {
    /* @objc */ func requiredMethod() {
        print("Default implementation")
    }
}

class ConformingClass: NSObject, ObjCProtocol {
    
}

ConformingClass().requiredMethod()

Error:

Untitled.swift:13:7: error: non-'@objc' method 'requiredMethod()' does not satisfy requirement of '@objc' protocol 'ObjCProtocol'
class ConformingClass: NSObject, ObjCProtocol {
      ^
Untitled.swift:8:19: note: add '@objc' to expose this instance method to Objective-C
        /* @objc */ func requiredMethod() {
                         ^
                    @objc 
Untitled.swift:4:13: note: requirement 'requiredMethod()' declared here
        @objc func requiredMethod()
                   ^

If you follow the fix-it, you another error which correctly tells you that this is invalid. But strangely, you still get a suggestion to add @objc:

Untitled.swift:8:3: error: @objc can only be used with members of classes, @objc protocols, and concrete extensions of classes
        @objc func requiredMethod() {
        ~^~~~~
        
Untitled.swift:13:7: error: non-'@objc' method 'requiredMethod()' does not satisfy requirement of '@objc' protocol 'ObjCProtocol'
class ConformingClass: NSObject, ObjCProtocol {
      ^
Untitled.swift:8:13: note: add '@objc' to expose this instance method to Objective-C
        @objc func requiredMethod() {
                   ^
        @objc 
Untitled.swift:4:13: note: requirement 'requiredMethod()' declared here
        @objc func requiredMethod()
                   ^
@typesanitizer
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@swift-ci create

@theblixguy
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#33891

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@theblixguy theblixguy

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation type checker Area → compiler: Semantic analysis
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@theblixguy @amomchilov @typesanitizer