Pitch: Multi-statement if/switch/do expressions

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What about the parsing issues of bare last statement? Unlike in SwiftUI @ViewBuilder contexts, in the contexts we’re discussing here the return type will very often be concrete, meaning that leading-dot syntax will be used often, but with no separating (non-whitespace) character or keyword between multiple expressions this will become ambiguous.

Imagine we start with this code:

var color: Color {
    if isSelected {
        .purple
    } else {
        .gray
    }
}

We want to add a print statement to the else branch, and the options under consideration so far are:

  1. A keyword (e.g., then)
  2. An operator (e.g., <-)
  3. No separator
  4. Semicolons

A keyword

var color: Color {
    if isSelected {
        .purple
    } else {
        print("Not selected")
        // Leading-dot syntax still works, but we had
        // to modify the return value using the keyword,
        // and also there are concerns about parsing a new keyword.
        then .gray
    }
}

An operator

var color: Color {
    if isSelected {
        .purple
    } else {
        print("Not selected")
        // Leading-dot syntax still works, but we had
        // to modify the return value using the operator.
        // At least we avoid issues related to parsing a new keyword.
        <- .gray
    }
}

No separator

var color: Color {
    if isSelected {
        .purple
    } else {
        print("Not selected")
        // Leading-dot syntax becomes ambiguous, so
        // we still end up having to modify
        // the line of the return value.
        Color.gray
    }
}

Semicolons

var color: Color {
    if isSelected {
        .purple
    } else {
        print("Not selected");
        // The only option that allows me to call `print(_:)`
        // without having to also modify the preexisting line.
        .gray
    }
}
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