Are all extensions from all modules exported on mass?


(Howard Lovatt) #1

Hi,

If I have the *same* extension in two *different* modules, ModuleA and
ModuleB, and ModuleC uses both modules, but in *seperate* files, then there
is still ambiguity about which extension to call:

ModuleA

A.swift

public protocol P {

func m() -> String

}

extension Int: P {

public func m() -> String { return "AP.m" }

}

ModuleB

B.swift

public protocol P {

func m() -> String

}
extension Int: P {

public func m() -> String { return "BP.m" }

}

ModuleC

A.swift

import ModuleA

func am(_ i: Int) -> String { return i.m() }

B.swift

import ModuleB

func bm(_ i: Int) -> String { return i.m() }

main.swift

let i = 0

print(am(i))
print(bm(i))

Gives the following errors when built:

sunzero-ln:ModuleC lov080$ swift build
Fetching /Users/lov080/Google Drive/Swift/Examples/Example Module
Clashes/ModuleA
Fetching /Users/lov080/Google Drive/Swift/Examples/Example Module
Clashes/ModuleB
Cloning /Users/lov080/Google Drive/Swift/Examples/Example Module
Clashes/ModuleA
Resolving /Users/lov080/Google Drive/Swift/Examples/Example Module
Clashes/ModuleA at 1.0.0
Cloning /Users/lov080/Google Drive/Swift/Examples/Example Module
Clashes/ModuleB
Resolving /Users/lov080/Google Drive/Swift/Examples/Example Module
Clashes/ModuleB at 1.0.0
Compile Swift Module 'ModuleB' (1 sources)
Compile Swift Module 'ModuleA' (1 sources)
Compile Swift Module 'ModuleC' (3 sources)
/Users/lov080/Google Drive/Swift/Examples/Example Module
Clashes/ModuleC/Sources/B.swift:3:38: error: ambiguous use of 'm()'
func bm(_ i: Int) -> String { return i.m() }
                                     ^
ModuleA.Int:2:17: note: found this candidate
    public func m() -> String
                ^
ModuleB.Int:2:17: note: found this candidate
    public func m() -> String
                ^
/Users/lov080/Google Drive/Swift/Examples/Example Module
Clashes/ModuleC/Sources/A.swift:3:38: error: ambiguous use of 'm()'
func am(_ i: Int) -> String { return i.m() }
                                     ^
ModuleA.Int:2:17: note: found this candidate
    public func m() -> String
                ^
ModuleB.Int:2:17: note: found this candidate
    public func m() -> String
                ^
<unknown>:0: error: build had 1 command failures
error: exit(1): /Applications/Xcode.app/Contents/Developer/Toolchains/
XcodeDefault.xctoolchain/usr/bin/swift-build-tool -f /Users/lov080/Google\
Drive/Swift/Examples/Example\ Module\ Clashes/ModuleC/.build/debug.yaml

Is this the expected behaviour or a bug?

Thanks in advance for any help,

  -- Howard.


(Jordan Rose) #2

It's a longstanding bug, but a bug we can't fix easily, and one whose fix would probably break user code. It's tracked by SR-3908 <https://bugs.swift.org/browse/SR-3908>. (The description's a little different but it's the same underlying issue.)

Jordan

···

On Apr 19, 2017, at 22:13, Howard Lovatt via swift-users <swift-users@swift.org> wrote:

Hi,

If I have the *same* extension in two *different* modules, ModuleA and ModuleB, and ModuleC uses both modules, but in *seperate* files, then there is still ambiguity about which extension to call:

ModuleA
A.swift
public protocol P {
func m() -> String
}
extension Int: P {
public func m() -> String { return "AP.m" }
}
ModuleB
B.swift
public protocol P {
func m() -> String
}
extension Int: P {
public func m() -> String { return "BP.m" }
}
ModuleC
A.swift
import ModuleA
func am(_ i: Int) -> String { return i.m() }
B.swift
import ModuleB
func bm(_ i: Int) -> String { return i.m() }
main.swift
let i = 0
print(am(i))
print(bm(i))

Gives the following errors when built:

sunzero-ln:ModuleC lov080$ swift build
Fetching /Users/lov080/Google Drive/Swift/Examples/Example Module Clashes/ModuleA
Fetching /Users/lov080/Google Drive/Swift/Examples/Example Module Clashes/ModuleB
Cloning /Users/lov080/Google Drive/Swift/Examples/Example Module Clashes/ModuleA
Resolving /Users/lov080/Google Drive/Swift/Examples/Example Module Clashes/ModuleA at 1.0.0
Cloning /Users/lov080/Google Drive/Swift/Examples/Example Module Clashes/ModuleB
Resolving /Users/lov080/Google Drive/Swift/Examples/Example Module Clashes/ModuleB at 1.0.0
Compile Swift Module 'ModuleB' (1 sources)
Compile Swift Module 'ModuleA' (1 sources)
Compile Swift Module 'ModuleC' (3 sources)
/Users/lov080/Google Drive/Swift/Examples/Example Module Clashes/ModuleC/Sources/B.swift:3:38: error: ambiguous use of 'm()'
func bm(_ i: Int) -> String { return i.m() }
                                     ^
ModuleA.Int:2:17: note: found this candidate
    public func m() -> String
                ^
ModuleB.Int:2:17: note: found this candidate
    public func m() -> String
                ^
/Users/lov080/Google Drive/Swift/Examples/Example Module Clashes/ModuleC/Sources/A.swift:3:38: error: ambiguous use of 'm()'
func am(_ i: Int) -> String { return i.m() }
                                     ^
ModuleA.Int:2:17: note: found this candidate
    public func m() -> String
                ^
ModuleB.Int:2:17: note: found this candidate
    public func m() -> String
                ^
<unknown>:0: error: build had 1 command failures
error: exit(1): /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-build-tool -f /Users/lov080/Google\ Drive/Swift/Examples/Example\ Module\ Clashes/ModuleC/.build/debug.yaml

Is this the expected behaviour or a bug?

Thanks in advance for any help,

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