func fancyThings() throws { }

func withTemporaryFile(filename: String = NSUUID().UUIDString, deleteWhenFinished: Bool = true, @noescape f: (NSURL) -> Void) { }

func AssertNoThrowNoAutoclosure<T>(expression: () throws -> T) {
    do {
        try expression()
    } catch {
        fatalError("Error was thrown when none were expected: \(error)")
    }
}

func AssertNoThrow<T>(@autoclosure expression: () throws -> T) {
    do {
        try expression()
    } catch {
        fatalError("Error was thrown when none were expected: \(error)")
    }
}


withTemporaryFile { tempFile -> Void in
//: Works fine, param is not autoclosure
    AssertNoThrowNoAutoclosure({ try fancyThings() })


/*: 
This triggers a compiler error even though autoclosure
    promotes the `try` into a closure; the `do` form below 
    should be equivalent since `AssertNoThrow` is not a 
    throwing function. Instead it attempts to promote the
    `withTemporaryFile` closure to throwing.
    
**error: invalid conversion from throwing function of type '_ throws -> Void' to non-throwing function type '(NSURL) -> Void'**
*/
    AssertNoThrow(try fancyThings())


/*:
Attempting to pass an explicit closure also confuses the compiler

**error: cannot invoke 'AssertNoThrow' with an argument list of type '(() throws -> ())'**
*/
    AssertNoThrow({ try fancyThings() })


/*: 
An explicit `do` still emits a warning because the compiler
correctly deduces that nothing can throw (the autoclosure 
hides the try)

**warning: 'catch' block is unreachable because no errors are thrown in 'do' block**
*/
    do {
        AssertNoThrow(try fancyThings())
    } catch { }
}