Open Radar

 
Summary:
ExtensibleCollectionType requires init(). I want my default initializer to optionally take a collection to initialize with. I can’t do this via default arguments; I have to provide two initializers instead.

The same applies to function requirements.

This is surprising and necessitates boilerplate.


Steps to Reproduce:
1. Try to compile this code:

protocol P {
	init()

	func f()
}

struct S1 : P {
	init() {}
	func f() {}
}

struct S2 : P {
	init(_ x: Int = 0) {}
	func f(_ x: Int = 0) {}
}



Expected Results:
“Build succeeded”


Actual Results:
./Protocol-default-args.swift:14:1: error: type 'S2' does not conform to protocol 'P'
struct S2 : P {
^
./Protocol-default-args.swift:4:2: note: protocol requires initializer 'init()' with type '()'
        init()
        ^
./Protocol-default-args.swift:15:2: note: candidate has non-matching type '(Int)'
        init(_ x: Int = 0) {}
        ^
./Protocol-default-args.swift:6:7: note: protocol requires function 'f()' with type '() -> ()'
        func f()
             ^
./Protocol-default-args.swift:16:7: note: candidate has non-matching type '(Int) -> ()'
        func f(_ x: Int = 0) {}
             ^


Regression:
N/A


Notes:
N/A