<h3 dir="auto">STR</h3>
<div class="highlight highlight-source-rust notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="fn main() {
    let mut v = vec![];
    write!(&amp;v, &quot;Hello world&quot;);
}"><pre class="notranslate"><span class="pl-k">fn</span> <span class="pl-en">main</span><span class="pl-kos">(</span><span class="pl-kos">)</span> <span class="pl-kos">{</span>
    <span class="pl-k">let</span> <span class="pl-k">mut</span> v = <span class="pl-en">vec</span><span class="pl-en">!</span><span class="pl-kos">[</span><span class="pl-kos">]</span><span class="pl-kos">;</span>
    <span class="pl-en">write</span><span class="pl-en">!</span><span class="pl-kos">(</span>&amp;v, <span class="pl-s">"Hello world"</span><span class="pl-kos">)</span><span class="pl-kos">;</span>
<span class="pl-kos">}</span></pre></div>
<h3 dir="auto">Output</h3>
<div class="highlight highlight-source-rust notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="$ time rustc write.rs
&lt;std macros&gt;:3:24: 3:14 error: cannot borrow immutable dereference of `&amp;`-pointer as mutable
&lt;std macros&gt;:3         let dst = &amp;mut *$dst;
[2]    2803 illegal hardware instruction (core dumped)  rustc write.rs
rustc write.rs  58.66s user 4.81s system 99% cpu 1:03.86 total"><pre class="notranslate">$ time rustc write<span class="pl-kos">.</span><span class="pl-c1">rs</span>
&lt;std macros&gt;<span class="pl-kos">:</span><span class="pl-c1">3</span><span class="pl-kos">:</span><span class="pl-c1">24</span><span class="pl-kos">:</span> <span class="pl-c1">3</span><span class="pl-kos">:</span><span class="pl-c1">14</span> error<span class="pl-kos">:</span> cannot borrow immutable dereference of `<span class="pl-c1">&amp;</span>`-pointer <span class="pl-k">as</span> <span class="pl-smi">mutable</span>
<span class="pl-kos">&lt;</span>std <span class="pl-smi">macros</span><span class="pl-kos">&gt;</span><span class="pl-kos">:</span><span class="pl-c1">3</span>         <span class="pl-k">let</span> dst = <span class="pl-c1">&amp;</span><span class="pl-k">mut</span> <span class="pl-c1">*</span>$dst<span class="pl-kos">;</span>
<span class="pl-kos">[</span><span class="pl-c1">2</span><span class="pl-kos">]</span>    <span class="pl-c1">2803</span> illegal hardware <span class="pl-en">instruction</span> <span class="pl-kos">(</span>core dumped<span class="pl-kos">)</span>  rustc write<span class="pl-kos">.</span><span class="pl-c1">rs</span>
rustc write<span class="pl-kos">.</span><span class="pl-c1">rs</span>  <span class="pl-c1">58.66</span>s user <span class="pl-c1">4.81</span>s system <span class="pl-c1">99</span>% cpu <span class="pl-c1">1</span><span class="pl-kos">:</span><span class="pl-c1">03.86</span> total</pre></div>
<h3 dir="auto">Backtrace</h3>
<div class="highlight highlight-source-rust notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="#0  0x00007ffff7351560 in oom::h6671a0e79ac45df3RTa () from /usr/lib64/librustrt-4e7c5e5c.so
#1  0x00007ffff499c535 in ?? () from /usr/lib64/libsyntax-4e7c5e5c.so
#2  0x00007ffff4a3fd27 in ?? () from /usr/lib64/libsyntax-4e7c5e5c.so
#3  0x00007ffff4a3b083 in diagnostic::EmitterWriter.Emitter::emit::h8944016a574210b0lrG ()
   from /usr/lib64/libsyntax-4e7c5e5c.so
#4  0x00007ffff4a398f9 in diagnostic::Handler::emit::hef6d94e096dac3f1F8F ()
   from /usr/lib64/libsyntax-4e7c5e5c.so
#5  0x00007ffff4a0c3ed in diagnostic::SpanHandler::span_err::he4174115bd82cc5fEWF ()
   from /usr/lib64/libsyntax-4e7c5e5c.so
#6  0x00007ffff5a77fea in middle::borrowck::BorrowckCtxt$LT$$x27a$C$$x20$x27tcx$GT$::report::h3050434306868883rEh () from /usr/lib64/librustc-4e7c5e5c.so
#7  0x00007ffff5a7d524 in middle::borrowck::gather_loans::GatherLoanCtxt$LT$$x27a$C$$x20$x27tcx$GT$.euv..Delegate$LT$$x27tcx$GT$::borrow::hd3a8e951ce2e3945bef () from /usr/lib64/librustc-4e7c5e5c.so
#8  0x00007ffff5a87421 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#9  0x00007ffff5a83d44 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#10 0x00007ffff5a830d0 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#11 0x00007ffff5a838d7 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#12 0x00007ffff5a876a9 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#13 0x00007ffff5a83091 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#14 0x00007ffff5a7ad31 in middle::borrowck::gather_loans::gather_loans_in_fn::ha2f120a3c6b6b70b96e ()
   from /usr/lib64/librustc-4e7c5e5c.so
#15 0x00007ffff5a9c574 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#16 0x00007ffff5a9961d in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#17 0x00007ffff5a9b666 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#18 0x00007ffff5a9a2f8 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#19 0x00007ffff5a99cc5 in middle::borrowck::check_crate::h7908f5f01a09671eOPg ()
   from /usr/lib64/librustc-4e7c5e5c.so
#20 0x00007ffff76a9917 in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#21 0x00007ffff7840568 in driver::driver::phase_3_run_analysis_passes::he238813c217c3b94efS ()
   from /usr/lib64/librustc_trans-4e7c5e5c.so
#22 0x00007ffff7833238 in driver::driver::compile_input::h117f94c1b348a398YVR ()
   from /usr/lib64/librustc_trans-4e7c5e5c.so
#23 0x00007ffff78b7cd7 in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#24 0x00007ffff78b62fc in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#25 0x00007ffff76c2f78 in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#26 0x00007ffff76c2e83 in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#27 0x00007ffff7bd6be2 in ?? () from /usr/lib64/libnative-4e7c5e5c.so
#28 0x00007ffff7390fec in ?? () from /usr/lib64/librustrt-4e7c5e5c.so
#29 0x00007ffff7390fd6 in rust_try () from /usr/lib64/librustrt-4e7c5e5c.so
#30 0x00007ffff733f843 in unwind::try::h03ead95328113b2fIZc () from /usr/lib64/librustrt-4e7c5e5c.so
#31 0x00007ffff733f70c in task::Task::run::hed7dc0cf620a0172y5b () from /usr/lib64/librustrt-4e7c5e5c.so
#32 0x00007ffff7bd69e7 in ?? () from /usr/lib64/libnative-4e7c5e5c.so
#33 0x00007ffff7340f35 in ?? () from /usr/lib64/librustrt-4e7c5e5c.so
#34 0x00007ffff1e0e294 in start_thread () from /lib64/libpthread.so.0
#35 0x00007ffff70181ed in clone () from /lib64/libc.so.6"><pre class="notranslate">#<span class="pl-c1">0</span>  <span class="pl-c1">0x00007ffff7351560</span> in oom<span class="pl-kos">::</span><span class="pl-en">h6671a0e79ac45df3RTa</span> <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustrt-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">1</span>  <span class="pl-c1">0x00007ffff499c535</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/libsyntax-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">2</span>  <span class="pl-c1">0x00007ffff4a3fd27</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/libsyntax-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">3</span>  <span class="pl-c1">0x00007ffff4a3b083</span> in diagnostic<span class="pl-kos">::</span><span class="pl-v">EmitterWriter</span><span class="pl-kos">.</span><span class="pl-c1">Emitter</span><span class="pl-kos">::</span>emit<span class="pl-kos">::</span><span class="pl-en">h8944016a574210b0lrG</span> <span class="pl-kos">(</span><span class="pl-kos">)</span>
   from /usr/lib64/libsyntax-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">4</span>  <span class="pl-c1">0x00007ffff4a398f9</span> in diagnostic<span class="pl-kos">::</span><span class="pl-smi">Handler</span><span class="pl-kos">::</span>emit<span class="pl-kos">::</span><span class="pl-en">hef6d94e096dac3f1F8F</span> <span class="pl-kos">(</span><span class="pl-kos">)</span>
   from /usr/lib64/libsyntax-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">5</span>  <span class="pl-c1">0x00007ffff4a0c3ed</span> in diagnostic<span class="pl-kos">::</span><span class="pl-smi">SpanHandler</span><span class="pl-kos">::</span>span_err<span class="pl-kos">::</span><span class="pl-en">he4174115bd82cc5fEWF</span> <span class="pl-kos">(</span><span class="pl-kos">)</span>
   from /usr/lib64/libsyntax-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">6</span>  <span class="pl-c1">0x00007ffff5a77fea</span> in middle<span class="pl-kos">::</span>borrowck<span class="pl-kos">::</span><span class="pl-smi">BorrowckCtxt</span>$LT$$x27a$C$$x20$x27tcx$GT$<span class="pl-kos">::</span>report<span class="pl-kos">::</span><span class="pl-en">h3050434306868883rEh</span> <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">7</span>  <span class="pl-c1">0x00007ffff5a7d524</span> in middle<span class="pl-kos">::</span>borrowck<span class="pl-kos">::</span>gather_loans<span class="pl-kos">::</span><span class="pl-smi">GatherLoanCtxt</span>$LT$$x27a$C$$x20$x27tcx$GT$<span class="pl-kos">.</span><span class="pl-c1">euv</span>..<span class="pl-smi">Delegate</span>$LT$$x27tcx$GT$<span class="pl-kos">::</span>borrow<span class="pl-kos">::</span><span class="pl-en">hd3a8e951ce2e3945bef</span> <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">8</span>  <span class="pl-c1">0x00007ffff5a87421</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">9</span>  <span class="pl-c1">0x00007ffff5a83d44</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">10</span> <span class="pl-c1">0x00007ffff5a830d0</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">11</span> <span class="pl-c1">0x00007ffff5a838d7</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">12</span> <span class="pl-c1">0x00007ffff5a876a9</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">13</span> <span class="pl-c1">0x00007ffff5a83091</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">14</span> <span class="pl-c1">0x00007ffff5a7ad31</span> in middle<span class="pl-kos">::</span>borrowck<span class="pl-kos">::</span>gather_loans<span class="pl-kos">::</span>gather_loans_in_fn<span class="pl-kos">::</span><span class="pl-en">ha2f120a3c6b6b70b96e</span> <span class="pl-kos">(</span><span class="pl-kos">)</span>
   from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">15</span> <span class="pl-c1">0x00007ffff5a9c574</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">16</span> <span class="pl-c1">0x00007ffff5a9961d</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">17</span> <span class="pl-c1">0x00007ffff5a9b666</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">18</span> <span class="pl-c1">0x00007ffff5a9a2f8</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">19</span> <span class="pl-c1">0x00007ffff5a99cc5</span> in middle<span class="pl-kos">::</span>borrowck<span class="pl-kos">::</span>check_crate<span class="pl-kos">::</span><span class="pl-en">h7908f5f01a09671eOPg</span> <span class="pl-kos">(</span><span class="pl-kos">)</span>
   from /usr/lib64/librustc-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">20</span> <span class="pl-c1">0x00007ffff76a9917</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc_trans-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">21</span> <span class="pl-c1">0x00007ffff7840568</span> in driver<span class="pl-kos">::</span>driver<span class="pl-kos">::</span>phase_3_run_analysis_passes<span class="pl-kos">::</span><span class="pl-en">he238813c217c3b94efS</span> <span class="pl-kos">(</span><span class="pl-kos">)</span>
   from /usr/lib64/librustc_trans-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">22</span> <span class="pl-c1">0x00007ffff7833238</span> in driver<span class="pl-kos">::</span>driver<span class="pl-kos">::</span>compile_input<span class="pl-kos">::</span><span class="pl-en">h117f94c1b348a398YVR</span> <span class="pl-kos">(</span><span class="pl-kos">)</span>
   from /usr/lib64/librustc_trans-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">23</span> <span class="pl-c1">0x00007ffff78b7cd7</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc_trans-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">24</span> <span class="pl-c1">0x00007ffff78b62fc</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc_trans-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">25</span> <span class="pl-c1">0x00007ffff76c2f78</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc_trans-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">26</span> <span class="pl-c1">0x00007ffff76c2e83</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustc_trans-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">27</span> <span class="pl-c1">0x00007ffff7bd6be2</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/libnative-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">28</span> <span class="pl-c1">0x00007ffff7390fec</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustrt-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">29</span> <span class="pl-c1">0x00007ffff7390fd6</span> in <span class="pl-en">rust_try</span> <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustrt-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">30</span> <span class="pl-c1">0x00007ffff733f843</span> in unwind<span class="pl-kos">::</span>try<span class="pl-kos">::</span><span class="pl-en">h03ead95328113b2fIZc</span> <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustrt-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">31</span> <span class="pl-c1">0x00007ffff733f70c</span> in task<span class="pl-kos">::</span><span class="pl-smi">Task</span><span class="pl-kos">::</span>run<span class="pl-kos">::</span><span class="pl-en">hed7dc0cf620a0172y5b</span> <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustrt-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">32</span> <span class="pl-c1">0x00007ffff7bd69e7</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/libnative-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">33</span> <span class="pl-c1">0x00007ffff7340f35</span> in ?? <span class="pl-kos">(</span><span class="pl-kos">)</span> from /usr/lib64/librustrt-<span class="pl-c1">4e7</span>c5e5c<span class="pl-kos">.</span><span class="pl-c1">so</span>
#<span class="pl-c1">34</span> <span class="pl-c1">0x00007ffff1e0e294</span> in <span class="pl-en">start_thread</span> <span class="pl-kos">(</span><span class="pl-kos">)</span> from /lib64/libpthread<span class="pl-kos">.</span><span class="pl-c1">so</span><span class="pl-kos">.</span><span class="pl-c1">0</span>
#<span class="pl-c1">35</span> <span class="pl-c1">0x00007ffff70181ed</span> <span class="pl-k">in</span> clone <span class="pl-kos">(</span><span class="pl-kos">)</span> from /lib64/libc<span class="pl-kos">.</span><span class="pl-c1">so</span><span class="pl-kos">.</span><span class="pl-c1">6</span></pre></div>
<h3 dir="auto">Version</h3>
<p dir="auto"><a class="commit-link" data-hovercard-type="commit" data-hovercard-url="https://github.com/rust-lang/rust/commit/1d81776209cfa2b5cb1825bdbf3965a7a7f0440a/hovercard" href="https://github.com/rust-lang/rust/commit/1d81776209cfa2b5cb1825bdbf3965a7a7f0440a"><tt>1d81776</tt></a></p>
<p dir="auto">Can anyone reproduce? I find this bizarre...</p>
<p dir="auto">cc <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/alexcrichton/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/alexcrichton">@alexcrichton</a> @jakub- <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sfackler/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/sfackler">@sfackler</a></p>
<p dir="auto">Compiling <a class="commit-link" data-hovercard-type="commit" data-hovercard-url="https://github.com/sfackler/rust-postgres/commit/1fa5941562739104d4a5fc39826f6ab7d27eb210/hovercard" href="https://github.com/sfackler/rust-postgres/commit/1fa5941562739104d4a5fc39826f6ab7d27eb210">sfackler/rust-postgres@<tt>1fa5941</tt></a> comes up with this on the current nightly, but not yesterday's:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="&lt;std macros&gt;:4:35: 4:50 error: type `&amp;mut [_]` does not implement any method in scope named `write_fmt`
&lt;std macros&gt;:4         format_args!(|args| { dst.write_fmt(args) }, $($arg)*)
                                                 ^~~~~~~~~~~~~~~
&lt;std macros&gt;:4:35: 4:50 error: type `&amp;mut [u8]` does not implement any method in scope named `write_fmt`
&lt;std macros&gt;:4         format_args!(|args| { dst.write_fmt(args) }, $($arg)*)
                                                 ^~~~~~~~~~~~~~~
&lt;std macros&gt;:4:35: 4:50 error: type `&amp;mut [_]` does not implement any method in scope named `write_fmt`
&lt;std macros&gt;:4         format_args!(|args| { dst.write_fmt(args) }, $($arg)*)
                                                 ^~~~~~~~~~~~~~~
&lt;std macros&gt;:4:35: 4:50 error: type `&amp;mut [u8]` does not implement any method in scope named `write_fmt`
&lt;std macros&gt;:4         format_args!(|args| { dst.write_fmt(args) }, $($arg)*)
                                                 ^~~~~~~~~~~~~~~
error: aborting due to 4 previous errors"><pre class="notranslate"><code class="notranslate">&lt;std macros&gt;:4:35: 4:50 error: type `&amp;mut [_]` does not implement any method in scope named `write_fmt`
&lt;std macros&gt;:4         format_args!(|args| { dst.write_fmt(args) }, $($arg)*)
                                                 ^~~~~~~~~~~~~~~
&lt;std macros&gt;:4:35: 4:50 error: type `&amp;mut [u8]` does not implement any method in scope named `write_fmt`
&lt;std macros&gt;:4         format_args!(|args| { dst.write_fmt(args) }, $($arg)*)
                                                 ^~~~~~~~~~~~~~~
&lt;std macros&gt;:4:35: 4:50 error: type `&amp;mut [_]` does not implement any method in scope named `write_fmt`
&lt;std macros&gt;:4         format_args!(|args| { dst.write_fmt(args) }, $($arg)*)
                                                 ^~~~~~~~~~~~~~~
&lt;std macros&gt;:4:35: 4:50 error: type `&amp;mut [u8]` does not implement any method in scope named `write_fmt`
&lt;std macros&gt;:4         format_args!(|args| { dst.write_fmt(args) }, $($arg)*)
                                                 ^~~~~~~~~~~~~~~
error: aborting due to 4 previous errors
</code></pre></div>
<p dir="auto">It's also a bit weird/concerning that there are no expansion traces.</p>