[rust-dev] Macros expanding to multiple statements

Ashish Myles marcianx at gmail.com
Sat Jan 11 18:40:26 PST 2014


Rust 0.9 indicates that support for expansion of macros into multiple
statements is now supported, and the following example from the test suite
works for me.
https://github.com/mozilla/rust/blob/master/src/test/run-pass/macro-multiple-items.rs

However, I receive an error for the following code

#[feature(macro_rules)];

macro_rules! my_print(
    ($a:expr, $b:expr) => (
        println!("{:?}", a);
        println!("{:?}", b);
    );
)

fn main() {
    let a = 1;
    let b = 2;
    my_print!(a, b);
}

(Note that the ^~~~~~~ below points at println.)

$ rustc macro_ignores_second_line.rs
macro_ignores_second_line.rs:6:9: 6:16 error: macro expansion ignores token
`println` and any following
macro_ignores_second_line.rs:6         println!("{:?}", b);
                                       ^~~~~~~
error: aborting due to previous error
task 'rustc' failed at 'explicit failure',
/home/marcianx/devel/rust/checkout/rust/src/libsyntax/diagnostic.rs:75
task '<main>' failed at 'explicit failure',
/home/marcianx/devel/rust/checkout/rust/src/librustc/lib.rs:453


What's the right way to do this?

Ashish
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