<p dir="auto">If you do <code class="notranslate">make install</code> with previous installed versions, multiple copies of all the libraries get left in (for me) <code class="notranslate">/usr/local/lib/rustc/x86_64-apple-darwin/lib</code>. Then the next time you try building something with the installed rustc, it'll promptly fail with <code class="notranslate">error: multiple matching crates for core</code></p>
<p dir="auto">It was disabled in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="50301165" data-permission-text="Title is private" data-url="https://github.com/rust-lang/rust/issues/19362" data-hovercard-type="pull_request" data-hovercard-url="/rust-lang/rust/pull/19362/hovercard" href="https://github.com/rust-lang/rust/pull/19362">#19362</a>. It'd be good to have it back one way or another.</p>