[swift-evolution] Obsoleting `if let`

[Brent Royal-Gordon]

> The original proposal says 
> 
> 	if let name? = optionalCondition { }
> 
> This would unwrap it? 
> 
> This seems like it should be mean the opposite.

The reason it unwraps it is that the thing on the left is a pattern, kind of like the cases of a case statement:

	switch optionalCondition {
	case let name?:
		// optionalCondition was not nil; name here is non-optional
	case nil:
		// optionalCondition was nil
	}

Think of it as the left side specifying a template the right side must match, with `let name` capturing the value corresponding to that particular position in the template.

-- 
Brent Royal-Gordon
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