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[SR-7839] Protocol Restricting Class Inheritance Cannot Consistently Access Valid Instance Properties #50375

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bscothern opened this issue Jun 1, 2018 · 1 comment
Closed

[SR-7839] Protocol Restricting Class Inheritance Cannot Consistently Access Valid Instance Properties #50375

bscothern opened this issue Jun 1, 2018 · 1 comment
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@slavapestov
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself

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@bscothern
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Previous ID SR-7839
Radar None
Original Reporter @bscothern
Type Bug
Status Resolved
Resolution Duplicate

Attachment: Download

Environment

macOS 10.13.4 – Apple Swift version 4.1.2 (swiftlang-902.0.54 clang-902.0.39.2

Ubuntu 16.04 (on arm) – Swift version 4.1.1 (swift-4.1.1-RELEASE)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee @slavapestov
Priority Medium

md5: 311941431a009031cc91fdaf1bd8655f

duplicates:

  • SR-6000 Let protocols inherit from class types

Issue Description:

When restricting a protocol to require inheritance from a specified class like so:

protocol SomeProtocol where Self: SomeClass {{{}}}

You are unable to access many properties of SomeClass outside of the same file as the declaration of SomeProtocol. I have experienced this on all apple platforms and ubuntu 16.04.

For example if you have the following files (which are attached and organized as a swift package) you will see all of the issues.

protocol SomeProtocol where Self: SomeClass {
}

extension SomeProtocol {
    func accessSomeClassProperty1FromSomeProtocolExtension() -> String {
        return Self.property1
    }
    
    func accessSomeClassProperty2FromSomeProtocolExtension() -> String {
        return property2
    }
}
class SomeClass {
    class var property1: String {
        return "1"
    }
    
    var property2: String {
        return "2"
    }
}
class Implementation: SomeClass, SomeProtocol {
}
func getSomeProtocol() -> SomeProtocol {
    return Implementation()
}

let someProtocol = getSomeProtocol()

print("=== Direct access through Implementation class/instance ===")
print("From Implementation class: " + Implementation.property1)
print("From new Implementation: " + Implementation().property2)

print("=== Access through SomeProtocol extension on Implementation instance ===")
print("From new Implementation: " + Implementation().accessSomeClassProperty1FromSomeProtocolExtension())
print("From new Implementation: " + Implementation().accessSomeClassProperty2FromSomeProtocolExtension())

print("=== Access through SomeProtocol extension on SomeProtocol instance ===")
print("From getSomeProtocol: " + someProtocol.accessSomeClassProperty1FromSomeProtocolExtension())
// This will crash
//print("From getSomeProtocol: " + someProtocol.accessSomeClassProperty2FromSomeProtocolExtension())

print("=== Access through Implementation instance through SomeProtocol instance ===")
// This case doesn't compile
//print("From getSomeProtocol: " + someProtocol.property2)
print("From getSomeProtocol as Implementation: " + (someProtocol as! SomeClass).property2)

For convenience here are the actual error outputs I have experienced.

Apple platforms:

Run time crash:

[1]    73553 bus error  swift run

Build failure:

swift build
Compile Swift Module 'ProtocolInheritClass' (4 sources)
/Users/Braden/Documents/Teal/Programming/SwiftBugs/ProtocolInheritClass/Sources/ProtocolInheritClass/main.swift:22:34: error: value of type 'SomeProtocol' has no member 'property2'
print("From getSomeProtocol: " + someProtocol.property2)
                                 ^~~~~~~~~~~~ ~~~~~~~~~
'ProtocolInheritClass' /Users/Braden/Documents/Teal/Programming/SwiftBugs/ProtocolInheritClass: warning: Ignoring duplicate product 'ProtocolInheritClass' 
error: terminated(1): /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-build-tool -f /Users/Braden/Documents/Teal/Programming/SwiftBugs/ProtocolInheritClass/.build/debug.yaml main output:

Ubuntu 16.04:

Build Failure

swift build
Compile Swift Module 'ProtocolInheritClass' (4 sources)
TYPE MISMATCH IN ARGUMENT 0 OF APPLY AT expression at [/home/tealdrone/ProtocolInheritClass/Sources/ProtocolInheritClass/main.swift:16:34 - line:16:97] RangeText="someProtocol.accessSomeClassProperty1FromSomeProtocolExtension()"
  argument value:   %227 = open_existential_addr immutable_access %3 : $*SomeProtocol to $*@opened("C95DABBC-6526-11E8-B001-00044B660A48") SomeProtocol
  parameter type: $@opened("C95DABBC-6526-11E8-B001-00044B660A48") SomeProtocol
/usr/bin/swift[0x3912d70]
Stack dump:
0.  Program arguments: /usr/bin/swift -frontend -c /home/tealdrone/ProtocolInheritClass/Sources/ProtocolInheritClass/Implementation.swift -primary-file /home/tealdrone/ProtocolInheritClass/Sources/ProtocolInheritClass/main.swift /home/tealdrone/ProtocolInheritClass/Sources/ProtocolInheritClass/SomeClass.swift /home/tealdrone/ProtocolInheritClass/Sources/ProtocolInheritClass/SomeProtocol.swift -target aarch64-unknown-linux -Xllvm -aarch64-use-tbi -disable-objc-interop -sdk / -I /home/tealdrone/ProtocolInheritClass/.build/aarch64-unknown-linux/debug -enable-testing -g -module-cache-path /home/tealdrone/ProtocolInheritClass/.build/aarch64-unknown-linux/debug/ModuleCache -swift-version 4 -Onone -D SWIFT_PACKAGE -color-diagnostics -emit-module-doc-path /home/tealdrone/ProtocolInheritClass/.build/aarch64-unknown-linux/debug/ProtocolInheritClass.build/main~partial.swiftdoc -module-name ProtocolInheritClass -emit-module-path /home/tealdrone/ProtocolInheritClass/.build/aarch64-unknown-linux/debug/ProtocolInheritClass.build/main~partial.swiftmodule -emit-dependencies-path /home/tealdrone/ProtocolInheritClass/.build/aarch64-unknown-linux/debug/ProtocolInheritClass.build/main.d -emit-reference-dependencies-path /home/tealdrone/ProtocolInheritClass/.build/aarch64-unknown-linux/debug/ProtocolInheritClass.build/main.swiftdeps -num-threads 4 -o /home/tealdrone/ProtocolInheritClass/.build/aarch64-unknown-linux/debug/ProtocolInheritClass.build/main.swift.o 
<unknown>:0: error: unable to execute command: Aborted
<unknown>:0: error: compile command failed due to signal 6 (use -v to see invocation)
'ProtocolInheritClass' /home/tealdrone/ProtocolInheritClass: warning: Ignoring duplicate product 'ProtocolInheritClass' 
error: terminated(1): /usr/bin/swift-build-tool -f /home/tealdrone/ProtocolInheritClass/.build/debug.yaml main output:
@belkadan
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belkadan commented Jun 1, 2018

@slavapestov, sounds like yet another manifestation of the other bugs we have on this?

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

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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself
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@belkadan @bscothern