SE-0415: Function Body Macros

[Douglas_Gregor]

@joshw

Could computed variables be declared via the "no-body" syntax functions can be declared with?

For example:

extension MyType {
    @Foo var name: String

    // expands to
    var name: String {
        "Foo"
    } 
}

(note this is in an extension so a stored property wouldn't be allowed here but leaving out the curly braces after the definition is more readable than not)

No, replacing a stored property with a computed property requires an accessor macro.

@wadetregaskis

Could preamble macros be replaced with wrapper macros

There's an "alternatives considered" section for this. I thought about it for a while and couldn't come up with a design that was a meaningful improvement over a body macro that calls a function with the original function body stuffed into a closure.

To have a macro produce boilerplate like what you show above, the macro implementation would be given some (opaque) variable names for the normal result and the error result, and then separately return code blocks to be executed on successful return (which gets the result value) and on thrown error (which gets the error value).

Doug