Support for macros in suffix / postfix position?

language design
7

Not really. In my suggestion the macro does not define how it needs self - in fact, it has not macro-level access to self (the expression before the macro) at all! All it does is generate tokens based on the macro arguments and replace the macro invocation (and it alone - not the tokens that come before it. Though the . does count as part of the macro invocation and gets replaces) with these tokens.

If I were to convert your example to my suggestion, it'd look like that (I'm using the style describe in this comment):

macro_rules! a(&self) {
    .() => {
        .match {
            this => {
                println!("{:?}", this.a);
                println!("{:?}", this.b);
            }
        }
    };
}

And then this:

do_something().a!();

Will resolve to:

do_something().match {
    this => {
        println!("{:?}", this.a);
        println!("{:?}", this.b);
    }
}

Which is equivalent to today's:

match do_something() {
    this => {
        println!("{:?}", this.a);
        println!("{:?}", this.b);
    }
}
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