Swift 2b4: Pointfree reference to generic initializer in generic context does not compile

Originator:rix.rob
Number:rdar://21928143 Date Originated:21-Jul-2015 05:30 PM
Status:Open Resolved:
Product:Developer Tools Product Version:Xcode-beta (7A165t)
Classification:Other Bug Reproducible:Always
 
Summary:
String.init works fine when the type it’s being applied to is well-known, but doesn’t seem to in a generic context.


Steps to Reproduce:
1. This code:
extension Array {
	func f() -> String {
		return ", ".join(lazy(self).map(String.init))
	}
}


Expected Results:
should compile

Actual Results:
but totally doesn’t:
rob@Resonance ~/Desktop> swiftc boom.swift
boom.swift:3:42: error: could not find an overload for 'String.init' that accepts the supplied arguments
                return ", ".join(lazy(self).map(String.init))
                                                ~~~~~~~^~~~

Regression:
It works fine if the type is known statically:
extension Array {
	func f() -> String {
		return ", ".join(lazy([1, 2, 3]).map(String.init))
	}
}

Notes:
N/A

Comments

Probably due to the overlapping generic init(_:) definitions

The following does compile: 

extension Array where Element : SequenceType, Element.Generator.Element == Character {
    func f() -> String {
        return ", ".join(lazy(self).map(String.init))
    }
}

which calls this String.init overload: 

init<S : SequenceType where S.Generator.Element == Character>(_ characters: S)

That suggests to me that swiftc is unable to figure out you'd want to unconditionally (?) call: 

init<T>(_ instance: T)

in your Array extension.

By pyry.jahkola at July 22, 2015, 7:24 a.m. (reply...)

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