<p dir="auto">On this page, <a href="https://doc.rust-lang.org/std/macro.unimplemented!.html" rel="nofollow">https://doc.rust-lang.org/std/macro.unimplemented!.html</a>, the [src] hyperlink points to <a href="https://doc.rust-lang.org/src/std/%3Ccore%20macros%3E.html#1" rel="nofollow">https://doc.rust-lang.org/src/std/%3Ccore%20macros%3E.html#1</a>, which does not exist.</p>
<p dir="auto">The same problem happens on <a href="https://doc.rust-lang.org/std/macro.format!.html" rel="nofollow">https://doc.rust-lang.org/std/macro.format!.html</a>, which points to <a href="https://doc.rust-lang.org/src/std/%3Ccore_collections%20macros%3E.html#1-2" rel="nofollow">https://doc.rust-lang.org/src/std/%3Ccore_collections%20macros%3E.html#1-2</a>.  The filename here is <code class="notranslate">&lt;core_collections macros&gt;.html</code>, which matches the name that <code class="notranslate">collections</code> is aliased to in libstd below.</p>
<p dir="auto">I think the problem happens with macros that are reexported from another crate.</p>
<p dir="auto">This seems to be a complete list of reexported macros in Rust's standard library:</p>
<p dir="auto">src/libstd/lib.rs:</p>
<div class="highlight highlight-source-rust notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="#[macro_use]
#[macro_reexport(assert, assert_eq, debug_assert, debug_assert_eq,
    unreachable, unimplemented, write, writeln)]
extern crate core;

#[macro_use]
#[macro_reexport(vec, format)]
extern crate collections as core_collections;"><pre class="notranslate"><span class="pl-c1">#<span class="pl-kos">[</span>macro_use<span class="pl-kos">]</span></span>
<span class="pl-c1">#<span class="pl-kos">[</span>macro_reexport<span class="pl-kos">(</span>assert, assert_eq, debug_assert, debug_assert_eq,</span>
<span class="pl-c1">    unreachable, unimplemented, write, writeln<span class="pl-kos">)</span><span class="pl-kos">]</span></span>
<span class="pl-k">extern</span> <span class="pl-k">crate</span> core<span class="pl-kos">;</span>

<span class="pl-c1">#<span class="pl-kos">[</span>macro_use<span class="pl-kos">]</span></span>
<span class="pl-c1">#<span class="pl-kos">[</span>macro_reexport<span class="pl-kos">(</span>vec, format<span class="pl-kos">)</span><span class="pl-kos">]</span></span>
<span class="pl-k">extern</span> <span class="pl-k">crate</span> collections <span class="pl-k">as</span> core_collections<span class="pl-kos">;</span></pre></div>
<p dir="auto">see <a href="http://doc.rust-lang.org/std/macro.assert!.html" rel="nofollow">http://doc.rust-lang.org/std/macro.assert!.html</a></p>