DistinctUntilChanged with boolean tuple behaves unexpectedly

[mickamy]

Short description of the issue:

Observable<(Bool, Bool)>.distinctUntilChanged behaives unexpectedly.

Observable<(Bool, Bool)>
    .of(
      (false, false),
      (true, false),
      (false, true),
      (true, true)
    )
    .distinctUntilChanged { $0 == $1 }
    .subscribe(onNext: { print("onNext: \($0)") })
    .disposed(by: bag)

Expected outcome:

onNext: (false, false)
onNext: (true, false)
onNext: (false, true)
onNext: (true, true)

What actually happens:

onNext: (false, false)
onNext: (true, false)
onNext: (true, true)

Self contained code example that reproduces the issue:

See above.
I also made a project for this.
https://github.com/mickamy/DistinctUntilChangedBugExample

This is not an issue belongs to Swift language I think.

print((false, false) == (true, false)) // false
print((true, false) == (false, true)) // false
print((false, true) == (true, true)) // false

RxSwift/RxCocoa/RxBlocking/RxTest version/commit

$ cat Podfile.lock
PODS:
  - RxCocoa (5.0.1):
    - RxRelay (~> 5)
    - RxSwift (~> 5)
  - RxRelay (5.0.1):
    - RxSwift (~> 5)
  - RxSwift (5.0.1)

DEPENDENCIES:
  - RxCocoa (~> 5)
  - RxSwift (~> 5)

SPEC REPOS:
  https://github.com/cocoapods/specs.git:
    - RxCocoa
    - RxRelay
    - RxSwift

SPEC CHECKSUMS:
  RxCocoa: e741b9749968e8a143e2b787f1dfbff2b63d0a5c
  RxRelay: 89d54507f4fd4d969e6ec1d4bd7f3673640b4640
  RxSwift: e2dc62b366a3adf6a0be44ba9f405efd4c94e0c4

PODFILE CHECKSUM: 1d020afcc2b600eb5b35469eadd8d975ae798179

COCOAPODS: 1.7.2

Platform/Environment

• iOS
• macOS
• tvOS
• watchOS
• playgrounds

How easy is to reproduce? (chances of successful reproduce after running the self contained code)

• easy, 100% repro
• sometimes, 10%-100%
• hard, 2% - 10%
• extremely hard, %0 - 2%

Xcode version:

$ xcodebuild -version
Xcode 11.1
Build version 11A1027

⚠️ Fields below are optional for general issues or in case those questions aren't related to your issue, but filling them out will increase the chances of getting your issue resolved. ⚠️

Installation method:

• CocoaPods
• Carthage
• Git submodules

I have multiple versions of Xcode installed:
(so we can know if this is a potential cause of your issue)

• yes (which ones)
• no

Level of RxSwift knowledge:
(this is so we can understand your level of knowledge
and formulate the response in an appropriate manner)

• just starting
• I have a small code base
• I have a significant code base

[mickamy]

Observable<(Bool, Bool)>
    .of(
        (false, false),
        (true, false),
        (false, true),
        (true, true)
    )
    .distinctUntilChanged({ $0 as (Bool, Bool) == $1 as (Bool, Bool) })
    .subscribe(onNext: { print("onNext: \($0)") })
    .disposed(by: bag)

onNext: (false, false)
onNext: (true, false)
onNext: (false, true)
onNext: (true, true)

Sorry it was Swift lang issue.

Somehow == in comparer { $0 == $1 } is taken as func == (lhs: Bool, rhs: Bool) -> Bool, which should be func == <A, B>(lhs: (A, B), rhs: (A, B)) -> Bool where A : Equatable, B : Equatable thou.

Gonna close this issue.