<REPL Input>:1:8: error: type 'X' does not conform to protocol 'P'
struct X : P { func f(_:(Int)->()) }
       ^
<REPL Input>:1:19: note: protocol requires function 'f' with type '((Int?) -> ()) -> ()'; do you want to add a stub?
protocol P { func f(_:(Int?)->()) }
                  ^
<REPL Input>:1:21: note: candidate has non-matching type '((Int) -> ()) -> ()'
struct X : P { func f(_:(Int)->()) }
                    ^
<REPL Input>:1:21: error: expected '{' in body of function declaration
struct X : P { func f(_:(Int)->()) }
                    ^
(swift) protocol Q { var i: Int? }
<REPL Input>:1:18: error: property in protocol must have explicit { get } or { get set } specifier
protocol Q { var i: Int? }
                 ^
(swift) protocol Q { var i: Int? {get}}
(swift) struct Y : Q { var i: Int = 0 }
<REPL Input>:1:8: error: type 'Y' does not conform to protocol 'Q'
struct Y : Q { var i: Int = 0 }
       ^
<REPL Input>:1:18: note: protocol requires property 'i' with type 'Int?'; do you want to add a stub?
protocol Q { var i: Int? {get}}
                 ^
<REPL Input>:1:20: note: candidate has non-matching type 'Int'
struct Y : Q { var i: Int = 0 }
                   ^
(swift) protocol R { func f() -> Int? }
(swift) struct Z : R { f() -> Int { return 3 } }
<REPL Input>:1:16: error: expected declaration
struct Z : R { f() -> Int { return 3 } }
               ^
<REPL Input>:1:8: note: in declaration of 'Z'
struct Z : R { f() -> Int { return 3 } }
       ^
<REPL Input>:1:8: error: type 'Z' does not conform to protocol 'R'
struct Z : R { f() -> Int { return 3 } }
       ^
<REPL Input>:1:19: note: protocol requires function 'f()' with type '() -> Int?'; do you want to add a stub?
protocol R { func f() -> Int? }
                  ^