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[SR-2266] Typealiased function-types are @escaping by default #44873

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karwa opened this issue Aug 3, 2016 · 4 comments
Closed

[SR-2266] Typealiased function-types are @escaping by default #44873

karwa opened this issue Aug 3, 2016 · 4 comments
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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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@karwa
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karwa commented Aug 3, 2016

Previous ID SR-2266
Radar None
Original Reporter @karwa
Type Bug
Status Resolved
Resolution Duplicate
Environment

Swift 6f743db

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

md5: 312a42469bcc5f7c24a5b6f50ae236fd

duplicates:

  • SR-2053 [Regression] Using @NoEscape for a type aliased closure results in a compile error

Issue Description:

The following code does not seem to be parseable:

protocol A { 
    associatedType Index 
    typealias TransformBlock = @noescape (_ oldIndex: Index, _ aParam: Bool) -> Index 
     
    mutating func doSomething(at: Index, with: TransformBlock) 
} 
error: repl.swift:3:43: error: expected type
    typealias TransformBlock = @noescape (_ oldIndex: Index, _ aParam: Bool) -> Index
                                          ^

error: repl.swift:3:43: error: expected ',' separator
    typealias TransformBlock = @noescape (_ oldIndex: Index, _ aParam: Bool) -> Index
                                          ^
                                          ,

error: repl.swift:3:62: error: expected type
    typealias TransformBlock = @noescape (_ oldIndex: Index, _ aParam: Bool) -> Index
                                                             ^

error: repl.swift:3:62: error: expected ',' separator
    typealias TransformBlock = @noescape (_ oldIndex: Index, _ aParam: Bool) -> Index
@belkadan
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belkadan commented Aug 3, 2016

I'm getting "use of undeclared type Index", which is better but not much.

@karwa
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karwa commented Aug 3, 2016

Also, a couple more points:

  • I removed the labels and it seemed to parse. However, any types which conform to the protocol do not inherit the typealias (no such member 'TransformBlock'), meaning I have to write the full expanded signatures in the implementation.

  • "@escaping" attributes have to be part of the typealias; you can't have an `@escaping TransformBlock` because the compiler complains `TransformBlock` is not a function-type.

@belkadan
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belkadan commented Aug 3, 2016

cc @milseman

@karwa
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karwa commented Aug 4, 2016

After more investigation:

  • The parameter label complaint seems to be some issue with SourceKit. The code compiles without errors, but as soon as I view the file Xcode will add a few errors of its own (`Expected type`, `Expected ',' separator`). I'll build again from `master` and see if maybe it's some kind of Xcode version thing.
  • You can access associated types. The diagnostics aren't very helpful, I don't know why it told you that:
// Works (but my Xcode displays an error because of aforementioned labels issue)
protocol MyProto {  
    associatedtype Blob
    typealias Executable = (_ argOne: Blob, _ argTwo: Bool)->()
    func execute(_ block: Executable)
}
  • Function typealiases seem to be escaping, rather than non-escaping, by default (whether in a protocol or not). This is the actual bug. It's a coincidence that the thing above affected the same declarations.
protocol MyProto {
    
    typealias Executable = ()->()
    func execute(_ block: Executable)
}

struct TestStruct : MyProto {

    // FIXME: SWIFT: We should inherit this from the protocol
    typealias Executable = ()->()

    func execute(_ block: Executable) {
        block()
    }

    private func doThing() {
        print("Doing a thing...")
    }

    mutating func execute_doThing() {
        execute {
            doThing()
        }
    }
}

Produces:

(source_file
  (protocol "MyProto"<Self : MyProto> type='MyProto.Protocol' access=internal @_fixed_layout
    (typealias "Executable" type='Executable.Type' access=internal type='() -> ()')
*    (func_decl "execute(_:)" type='<Self : MyProto> (Self) -> (Executable) -> ()' interface type='<τ_0_0 where τ_0_0 : MyProto> (τ_0_0) -> (@escaping () -> ()) -> ()' access=internal
      (parameter_list
        (parameter "self" type='Self'))
      (parameter_list
        (parameter "block" type='Executable'))))
  (struct_decl "TestStruct" type='TestStruct.Type' access=internal @_fixed_layout inherits: MyProto
    (typealias "Executable" type='Executable.Type' access=internal type='() -> ()')
*    (func_decl "execute(_:)" type='(TestStruct) -> (Executable) -> ()' interface type='(TestStruct) -> (@escaping () -> ()) -> ()' access=internal
      (conformance test.(file).MyProto.execute@/Users/karl/Desktop/test.swift:4:7)
      (parameter_list
        (parameter "self" type='TestStruct'))
      (parameter_list
        (parameter "block" type='Executable'))
      (brace_stmt
        (call_expr type='()' location=/Users/karl/Desktop/test.swift:13:3 range=[/Users/karl/Desktop/test.swift:13:3 - line:13:9] nothrow  arg_labels=
          (declref_expr type='() -> ()' location=/Users/karl/Desktop/test.swift:13:3 range=[/Users/karl/Desktop/test.swift:13:3 - line:13:3] decl=test.(file).TestStruct.func decl.block@/Users/karl/Desktop/test.swift:12:17 function_ref=single specialized=no)
          (tuple_expr type='()' location=/Users/karl/Desktop/test.swift:13:8 range=[/Users/karl/Desktop/test.swift:13:8 - line:13:9]))))
  • You can't add `@escaping` or `@noescape` to a parameter whose type is a typealiased-function (the typealias is not considered to be a function-type)

@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 @karwa