[swift-evolution] Proposal Draft: Optional Upgrading Assignment.

[Radosław Pietruszewski]

What’s your use case for this? I don’t find myself doing this very often.

And when I do, Optional(x) does the job.

> Draft Proposal feedback welcome.
> 
> ## Introduction
> 
> Currently to make a optional from a value the type name must be repeated:
> 
> let x = “Some Value”
> let y : String? = x
> 
> This takes away some of the advantage of type inference because the very next line I must specify the type.
> 
> ## Proposal
> 
> I propose the following syntax:
> 
> let y? = x
> 
> This binds a new optional y which wraps the same value of x. It follows the same conventions asvarandletthat currently exist in the language.
> 
> The advantages: this is easier to read, more compact, and lets type inference determine the type.
> 
> If letand other conditionals would not support this syntax and optionals of optionals is not supported. So let x?? = y would not result in an optional optional. Also if y was an optional it would not let you upgrade that.
> 
> ## Detailed Design
> 
> The grammar:
> 
> let optionalValue? = value
> 
> This would not make sense in theif let, (guardlet)context becauseif letunwraps the value, so this would be an error.
> 
> This should not conflict with pattern matching as that requires thecasekeyword.
> 
> Wrapping optional in an optional is an error.
> 
> ## Impact on existing code
> 
> The current syntax will continue to exist so it will have no impact on existing code.
> 
> ## Alternatives Considered
> 
> None.
> 
> 
> 
> 
>  

— Radek