<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="fn main() {
    println!(format!(&quot;{}&quot;,123));
}"><pre class="notranslate"><code class="notranslate">fn main() {
    println!(format!("{}",123));
}
</code></pre></div>
<p dir="auto">When compiled, rustc will prints:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!(&quot;{}&quot;,123));
                     ^~~~~~
macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!(&quot;{}&quot;,123));
                     ^~~~~~
macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!(&quot;{}&quot;,123));
                     ^~~~~~
macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!(&quot;{}&quot;,123));
                     ^~~~~~
macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!(&quot;{}&quot;,123));
............"><pre class="notranslate"><code class="notranslate">macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!("{}",123));
                     ^~~~~~
macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!("{}",123));
                     ^~~~~~
macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!("{}",123));
                     ^~~~~~
macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!("{}",123));
                     ^~~~~~
macro.c:12:11: 12:17 error: macro undefined: 'format'
macro.c:12  println!(format!("{}",123));
............
</code></pre></div>
<p dir="auto">Apologies if this has been reported before.  A search didn't turn up anything but you know how GH's search is.</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="$ cat t.rs
fn main() { print!(format!(&quot;BAM&quot;)); }

$ rustc t.rs 2&gt;&amp;1 | head -20
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!(&quot;BAM&quot;)); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!(&quot;BAM&quot;)); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!(&quot;BAM&quot;)); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!(&quot;BAM&quot;)); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!(&quot;BAM&quot;)); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!(&quot;BAM&quot;)); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!(&quot;BAM&quot;)); }"><pre class="notranslate"><code class="notranslate">$ cat t.rs
fn main() { print!(format!("BAM")); }

$ rustc t.rs 2&gt;&amp;1 | head -20
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!("BAM")); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!("BAM")); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!("BAM")); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!("BAM")); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!("BAM")); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!("BAM")); }
                          ^~~~~~
t.rs:1:20: 1:26 error: macro undefined: 'format'
t.rs:1 fn main() { print!(format!("BAM")); }
</code></pre></div>
<p dir="auto">Tested with today's x86_64 lucid nightly from <a href="https://launchpad.net/~hansjorg/+archive/rust" rel="nofollow">https://launchpad.net/~hansjorg/+archive/rust</a></p>