Swift fails to select correct overloaded function with Decimal

[jasonbobier]

The following code produces the error: member 'attributed' in 'Decimal.FormatStyle' produces result of type 'Decimal.FormatStyle.Attributed', but context expects 'Decimal.FormatStyle

public func formatted(_ formatStyle: Decimal.FormatStyle) -> String {
	Decimal(1).formatted(formatStyle)
}

public func formatted(_ formatStyle: Decimal.FormatStyle.Attributed) -> AttributedString {
	Decimal(1).formatted(formatStyle)
}

formatted(.number.attributed)

But this code works fine:

public func formatted(_ formatStyle: IntegerFormatStyle<Int>) -> String {
	1.formatted(formatStyle)
}

public func formatted(_ formatStyle: IntegerFormatStyle<Int>.Attributed) -> AttributedString {
	1.formatted(formatStyle)
}

formatted(IntegerFormatStyle<Int>.number.attributed)

Environment

• Swift compiler version info: swift-driver version: 1.62.15 Apple Swift version 5.7.2 (swiftlang-5.7.2.135.5 clang-1400.0.29.51)
  Target: arm64-apple-macosx13.0

• Xcode version info: Version 14.2 (14C18)

[LucianoPAlmeida]

I think this is expected behavior, to make the first case to work we have to specify the base formatted(Decimal.FormatStyle.number.attributed) because basically when base is not specified .number.attributed when attempting each overload solver will try infere base from context which in for first overload that takes Decimal.FormatStyle base will be attempted as **Decimal.FormatStyle**.number.attributed which fails with mismatch because the result of it is Decimal.FormatStyle.Attributed but parameter expects Decimal.FormatStyle. And when attempting second overload that takes Decimal.FormatStyle.Attributed base will be inferred as **Decimal.FormatStyle.Attributed**.number.attributed which fails because that type has no member number.
This results in no overload matching formatted(.number.attributed)
Note that second example works because you do specify base.

[jasonbobier]

Yep. That makes sense to me as well. And once Foundation is open sourced, I'll sneak in a .number for Decimal.FormatStyle.Attributed, so it all looks pleasant. :)

[LucianoPAlmeida]

We could get away with that by using extensions in your context

public func formatted(_ formatStyle: Decimal.FormatStyle) -> String {
  Decimal(1).formatted(formatStyle)
}

public func formatted(_ formatStyle: Decimal.FormatStyle.Attributed) -> AttributedString {
  Decimal(1).formatted(formatStyle)
}

extension Decimal.FormatStyle.Attributed {
  static var number: Decimal.FormatStyle.Attributed { Decimal.FormatStyle.number.attributed }
}

// Now inference can work with `Decimal.FormatStyle.Attributed` as base.
let _: AttributedString = formatted(.number) // Picks second overload
let _: String =  formatted(.number) // Picks first overload 

[jasonbobier]

That's almost what I did. I extended it like this:

public func formatted(_ formatStyle: Decimal.FormatStyle) -> String {
	Decimal(1).formatted(formatStyle)
}

public func formatted(_ formatStyle: Decimal.FormatStyle.Attributed) -> AttributedString {
	Decimal(1).formatted(formatStyle)
}

extension Decimal.FormatStyle.Attributed {
	static var number: Decimal.FormatStyle { Decimal.FormatStyle.number }
}

formatted(.number)
formatted(.number.attributed)

To keep .number and .number.attributed consistent in meaning with their current versions (.i.e. number is String based and number.attributed is AttributedString based).