Open Radar

 
Summary:
The following line has an implicit return of Int(10) and generates an error message of "'Int' is not convertible to 'Void'".

    var caller1 = { () -> Void in 5 + 5 }

That's reasonable.

The following method has an implicit return of Void and doesn't generate an error:

    var x:[Int]?
    var caller2 = { () -> Void in x!.append(5) }

This third method has an implicit return type of Optional<Void> and should generate an error message of "'Void?' is not convertible to 'Void'".

    var x:[Int]?
    var caller3 = { () -> Void in x?.append(5) }

Instead it returns a cryptic error message:

    Cannot convert the expression's type '() -> Void to type Int'

It seems like the parser may be trying to turn it into something else because the following two methods compile once the return type becomes Void:

    var x:[Int]?
    var caller3ret = { () -> Void in x?.append(5); return }
    var caller3bang = { () -> Void in (x?.append(5))! }

Steps to Reproduce:
Paste the following into a storyboard.  Gawk at the resulting message:


    var x:[Int]?
    var caller3 = { () -> Void in x?.append(5) }

Expected Results:
A reasonable error message. Maybe something special since Void? is not a common type.

Actual Results:
Weird error message:

Cannot convert the expression's type '() -> Void to type Int'

Version:
Yosemite seed 10.1, Xcode 6.1