<p dir="auto">As I mentioned on <a href="https://discourse.julialang.org/t/issetequal-behavior-with-duplicate-elements/26238" rel="nofollow">Discourse</a>, the <code class="notranslate">issetequal</code> docstring says that <code class="notranslate">issetequal(a, b)</code> is equivalent to <code class="notranslate">a ⊆ b &amp;&amp; b ⊆ a</code>, but this isn't the case when there are duplicate elements:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="julia&gt; versioninfo()
Julia Version 1.0.0
Commit 5d4eaca0c9 (2018-08-08 20:58 UTC)
Platform Info:
OS: macOS (x86_64-apple-darwin14.5.0)
CPU: Intel(R) Core(TM) i5-5257U CPU @ 2.70GHz
WORD_SIZE: 64
LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, broadwell)

julia&gt; a = [1,2,3];

julia&gt; b = [1,1,2,3];

julia&gt; a ⊆ b &amp;&amp; b ⊆ a
true

julia&gt; issetequal(a, b)
false"><pre class="notranslate"><code class="notranslate">julia&gt; versioninfo()
Julia Version 1.0.0
Commit 5d4eaca0c9 (2018-08-08 20:58 UTC)
Platform Info:
OS: macOS (x86_64-apple-darwin14.5.0)
CPU: Intel(R) Core(TM) i5-5257U CPU @ 2.70GHz
WORD_SIZE: 64
LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, broadwell)

julia&gt; a = [1,2,3];

julia&gt; b = [1,1,2,3];

julia&gt; a ⊆ b &amp;&amp; b ⊆ a
true

julia&gt; issetequal(a, b)
false
</code></pre></div>
<p dir="auto">This is because the <a href="https://github.com/JuliaLang/julia/blob/master/base/abstractset.jl#L291">implementation</a> assumes no duplicate elements:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="issetequal(l, r) = length(l) == length(r) &amp;&amp; l ⊆ r"><pre class="notranslate"><code class="notranslate">issetequal(l, r) = length(l) == length(r) &amp;&amp; l ⊆ r
</code></pre></div>
<p dir="auto">Due to <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="53167972" data-permission-text="Title is private" data-url="https://github.com/JuliaLang/julia/issues/9513" data-hovercard-type="issue" data-hovercard-url="/JuliaLang/julia/issues/9513/hovercard" href="https://github.com/JuliaLang/julia/issues/9513">#9513</a>, we've decided to push the 0.3.5 release up two weeks, shooting for this weekend for a new release.  Let's discuss here what we want to try and include in this release.  Although it is motivated by a single issue, I see no reason to avoid other fixes that have already been merged into <code class="notranslate">release-0.3</code>/are close to being merged.  In short, this should be a fully-fledged release, not a targeted bugfix.</p>