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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - c++2a: unable to set attributes to defaulted member functions"
href="https://bugs.llvm.org/show_bug.cgi?id=41991">41991</a>
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<th>Summary</th>
<td>c++2a: unable to set attributes to defaulted member functions
</td>
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>8.0
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++2a
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>development@jordi.vilar.cat
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>The following code, compiled with clang-8 -std=c++2a, fails with:
error: an attribute list cannot appear here
(it also issues error: only special member functions may be defaulted, but this
is reported in a separated bug report #41989)
#include <compare>
struct type
{
// original
[[nodiscard]] friend constexpr std::strong_equality operator<=>(const
type&, const type&) noexcept = default;
// variant #1
// [[nodiscard]] friend constexpr std::strong_equality operator<=>(const
type&, const type&) noexcept;
// variant #2
// [[nodiscard]] friend constexpr std::strong_equality operator<=>(const
type&, const type&) noexcept { return std::strong_ordering::equal; }
};
With variant #1, clang complaints with the same error, this time is correct as
attribues for friend declarations are not allowed as per specs.
With variant #2, clang accepts the code with no complaints as the friend
operator is now a definition and attributes are allowed in this case.
With the original variant, clang applies the rule for friend declaration when
in fact it is a (implicit) definition, that is, the friend operator is not
expected to be later defined.</pre>
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