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[SR-5298] Swift 3.2 source breakage on C enum import #47873

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swift-ci opened this issue Jun 24, 2017 · 7 comments
Closed

[SR-5298] Swift 3.2 source breakage on C enum import #47873

swift-ci opened this issue Jun 24, 2017 · 7 comments
Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 4.0

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@swift-ci
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Previous ID SR-5298
Radar rdar://problem/33007372
Original Reporter florent.bruneau (JIRA User)
Type Bug
Status Resolved
Resolution Won't Do
Environment

Linux

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, 4.0Regression, ClangImporter
Assignee None
Priority Medium

md5: 358d6880992e49579a58a90bae318431

Issue Description:

I import the following C enum in Swift:

typedef enum ic__ic_priority__t {
    IC_PRIORITY_LOW,
    IC_PRIORITY_NORMAL,
    IC_PRIORITY_HIGH,
} ic__ic_priority__t;

With Swift 3.1, the enum is imported as a RawRepresable with RawValue = Int32, while in Swift 3.2, the RawValue becomes an UInt32 causing compilation error even when enforcing the -swift-version 3 flag.
@belkadan
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I'm afraid we'll need more context than this. Where is this enum defined? What are the definitions of the IC_* constants on your version of the OS?

@swift-ci
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Comment by Florent Bruneau (JIRA)

In order to reproduce you can use those three files:

module.map:

module blah {
    header "blah.h"
}

blah.h:

typedef enum ic__ic_priority__t {
    IC_PRIORITY_LOW,
    IC_PRIORITY_NORMAL,
    IC_PRIORITY_HIGH,
} ic__ic_priority__t;

and blah.swift:

protocol MyEnumWrapper : RawRepresentable {
    typealias RawValue = Int32
}

extension ic__ic_priority__t : MyEnumWrapper { }

Then run the following command in the directory where you put the three files:

swiftc -swift-version 3 -I. -emit-module -module-name blah -import-underlying-module blah.swift

With swift 3.1, this works without any warning.
With swift 3.2, I got the following output:

blah.swift:2:15: warning: typealias overriding associated type 'RawValue' from protocol 'RawRepresentable' is better expressed as same-type constraint on the protocol
    typealias RawValue = Int32
    ~~~~~~~~~~^~~~~~~~~~~~~~~~

Swift.RawRepresentable:94:20: note: 'RawValue' declared here
    associatedtype RawValue
                   ^
blah.swift:5:1: error: 'MyEnumWrapper' requires the types 'ic__ic_priority__t.RawValue' (aka 'UInt32') and 'Int32' be equivalent
extension ic__ic_priority__t : MyEnumWrapper { }
^
blah.swift:5:1: note: requirement specified as 'Self.RawValue' == 'Int32' [with Self = ic__ic_priority__t]
extension ic__ic_priority__t : MyEnumWrapper { }
^

@belkadan
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Huh. Thanks, Florent!

@swift-ci create

@belkadan
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Okay, as far as I can tell nothing has changed in how we import the enum—i.e. it's always had a UInt32 raw type. So what's changed is that we've gotten better at telling that all your associated types need to be consistent.

@belkadan
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@slavapestov, do you remember where we had this discussion? I found SR-4382, but I remember us talking somewhere else as well.

@belkadan
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Florent, you can confirm that the old behavior used UInt32 with this code:

protocol MyEnumWrapper : RawRepresentable {
    typealias RawValue = Int32
}

extension ic__ic_priority__t : MyEnumWrapper { }

func getRawType<T: RawRepresentable>(_: T.Type) -> T.RawValue.Type {
  return T.RawValue.self
}
print(ic__ic_priority__t.RawValue.self)
print(getRawType(ic__ic_priority__t.self))

@swift-ci
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Comment by Florent Bruneau (JIRA)

Hi Jordan,

You're right, the RawValue is indeed an UInt32 with Swift 3.1

% swiftc -swift-version 3 -I. -module-name blah -import-underlying-module blah.swift
% ./blah
UInt32
UInt32

Unless the enum contains some negative values, in which case it switches to Int32.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 4.0
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@belkadan @swift-ci @AnthonyLatsis