[SR-9777] SourceKit's 'editor open' request not returning correct accessibility value in Swift 5

[jpsim]

Previous ID	SR-9777
Radar	None
Original Reporter	@jpsim
Type	Bug

Additional Detail from JIRA

Votes	1
Component/s	Source Tooling
Labels	Bug
Assignee	@akyrtzi
Priority	Medium

md5: c83ce94350f84a6accca1bec8eed73bc

Issue Description:

For instance members of a private type with no explicit ACL annotation, SourceKit from Swift 4.x correctly inferred an ACL of private.

SourceKit from the Swift 5 preview included in Xcode 10.2 beta 1 incorrectly infers an ACL of internal.

I believe this to be a regression in Swift 5 compared to Swift 4.2.1 (and versions going back quite a bit, at least to 4.0 if not earlier).

Note that I'm just using 3rd party tools like SourceKitten and jq to simplify this demonstration, this problem is present without them.

$ cat file.swift
private class Foo {
  func bar() {}
}
$ cat request.yml
key.request: source.request.editor.open
key.name: "/tmp/SR-9777/file.swift"
key.sourcefile: "/tmp/SR-9777/file.swift"
$ brew install sourcekitten
$ DEVELOPER_DIR=/Applications/Xcode-10.1.app/Contents/Developer sourcekitten request --yaml request.yml | jq '."key.substructure"'
[
  {
    "key.accessibility": "source.lang.swift.accessibility.private",
    "key.attributes": [
      {
        "key.attribute": "source.decl.attribute.private",
        "key.length": 7,
        "key.offset": 0
      }
    ],
    "key.bodylength": 17,
    "key.bodyoffset": 19,
    "key.kind": "source.lang.swift.decl.class",
    "key.length": 29,
    "key.name": "Foo",
    "key.namelength": 3,
    "key.nameoffset": 14,
    "key.offset": 8,
    "key.runtime_name": "_TtC4main3Foo",
    "key.substructure": [
      {
        "key.accessibility": "source.lang.swift.accessibility.private",
        "key.bodylength": 0,
        "key.bodyoffset": 34,
        "key.kind": "source.lang.swift.decl.function.method.instance",
        "key.length": 13,
        "key.name": "bar()",
        "key.namelength": 5,
        "key.nameoffset": 27,
        "key.offset": 22
      }
    ]
  }
]
$ DEVELOPER_DIR=/Applications/Xcode-10.2.app/Contents/Developer sourcekitten request --yaml request.yml | jq '."key.substructure"'
[
  {
    "key.accessibility": "source.lang.swift.accessibility.private",
    "key.attributes": [
      {
        "key.attribute": "source.decl.attribute.private",
        "key.length": 7,
        "key.offset": 0
      }
    ],
    "key.bodylength": 17,
    "key.bodyoffset": 19,
    "key.kind": "source.lang.swift.decl.class",
    "key.length": 29,
    "key.name": "Foo",
    "key.namelength": 3,
    "key.nameoffset": 14,
    "key.offset": 8,
    "key.runtime_name": "_TtC4mainP33_DC7C78BA85A59EC6A4D8097C64295BD73Foo",
    "key.substructure": [
      {
        "key.accessibility": "source.lang.swift.accessibility.internal",
        "key.bodylength": 0,
        "key.bodyoffset": 34,
        "key.kind": "source.lang.swift.decl.function.method.instance",
        "key.length": 13,
        "key.name": "bar()",
        "key.namelength": 5,
        "key.nameoffset": 27,
        "key.offset": 22
      }
    ]
  }
]

[marcelofabri]

This also happens on the latest 5.0 and master snapshots.

[belkadan]

Technically internal is correct according to SE-0025, but I agree it's not necessarily the most useful answer.

[jpsim]

Ah, very interesting @belkadan, I hadn't seen this paragraph from SE-0025:

The compiler should not warn when a broader level of access control is used within a type with more restrictive access, such as internal within a private type. This allows the designer of the type to select the access they would use were they to make the type more widely accessible. (The members still cannot be accessed outside the enclosing lexical scope because the type itself is still restricted, i.e. outside code will never encounter a value of that type.)

Thanks for sharing! Seems like the effective visibility of those declarations is actually fileprivate however, which is what I would expect SourceKit to return.

Though I just noticed that members with an inferred ACL don't have a "key.attribute": "source.decl.attribute.private" so I think we can leverage this as a workaround for realm/SwiftLint#2607 .