[SR-3318] Operator matching bug

[an0]

Previous ID	SR-3318
Radar	None
Original Reporter	@an0
Type	Bug

Environment

Swift 3.0.1

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, 3.0Regression, TypeChecker
Assignee	None
Priority	Medium

md5: 198b215af0ca093eeba57a059779685a

Issue Description:

public prefix func - (v: CGVector) -> CGVector {
    return CGVector(dx: -v.dx, dy: -v.dy)
}

public func + (p: CGPoint, v: CGVector) -> CGPoint {
    return CGPoint(x: p.x + v.dx, y: p.y + v.dy)
}

public func - (p: CGPoint, v: CGVector) -> CGPoint {
    return p + (-v)
}

public func - (lhs: CGPoint, rhs: CGPoint) -> CGVector {
    return CGVector(dx: rhs.x - lhs.x, dy: rhs.y - lhs.y)
}


let points = [CGPoint.zero, CGPoint.zero, CGPoint.zero]
let startPoint = points[0] - (points[1] - points[0]) // ambiguous reference to member '-'

Compiler reports this error:

error: ambiguous reference to member '-'
let startPoint = points[0] - (points[1] - points[0])
                                        ^

note: found this candidate
public func - (p: CGPoint, v: CGVector) -> CGPoint {
            ^

note: found this candidate
public func - (lhs: CGPoint, rhs: CGPoint) -> CGVector {
            ^

I don't see how this is ambiguous.

[an0]

It is a regression because the same code compiles in Swift 2.3.