protocol Foo {}
protocol Fooo: Foo {}

class A: Foo {}

protocol Soo1: Foo & Foo {} 
// Xcode 9.2:  
//     error: Duplicate inheritance from 'Foo'
//     error: Protocol-constrained type is neither allowed nor needed here
//     warning: Redundant conformance constraint 'Self: Foo'
// 
// Xcode 9.4 beta: Nothing
//
// Suggested warning: Duplicate inheritance from 'Foo'


protocol Soo2: Foo & Fooo {}
// Xcode 9.2:  
//     error: Protocol-constrained type is neither allowed nor needed here
//     warning: Redundant conformance constraint 'Self: Foo'
//
// Xcode 9.4 beta: Nothing
//
// Suggested warning: Redundant conformance constraint 'Self: Foo' 



// Xcode 9.2 & Xcode 9.4 beta: Nothing

func foo1(_ arg: A & Foo) {} 
// Suggested warning:
// Redundant conformance of protocol-constrained type (or existential type) to 'Foo'  

func foo2(_ arg: A & A) {} 
// Suggested warning:
// Protocol-constrained type (or existential type) already contains class 'A'  

func foo3(_ arg: Foo & Foo) {} 
// Suggested warning:
// Redundant conformance of protocol-constrained type (or existential type) to 'Foo' [or]  Protocol-constrained type (or existential type) already contains protocol 'Foo'  

func foo4(_ arg: Fooo & Foo) {} 
// Suggested warning:
// Redundant conformance of protocol-constrained type (or existential type) to 'Foo'