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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - member using declaration of function templates with different return types does not bring base class overload into derived class"
href="https://bugs.llvm.org/show_bug.cgi?id=50239">50239</a>
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<th>Summary</th>
<td>member using declaration of function templates with different return types does not bring base class overload into derived class
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>gonzalo.gadeschi@gmail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>Clang incorrectly accepts the following example
(<a href="https://clang.godbolt.org/z/7abPjfcf6">https://clang.godbolt.org/z/7abPjfcf6</a>):
template <class T> struct A {
template <class U> long f(U) const { return 1; }
};
struct B : A<int> {
using A<int>::f;
template <class U> int f(U) const { return 2; }
};
int main() {
return B{}.f(3);
}
Instead, it should error at "B{}.f(3)", since the call is ambiguous.
A member using declaration brings into the derived class all the overloads of
the specified function from the given base class, except for any overloads
where the derived class has a function declaration with the same signature
([namespace.udecl]/p11).
For non-template functions, the return type is not part of the signature
([defns.signature.member]).
For function templates, the return type is part of the signature
([defns.signature.member.templ]).
In this example, A<int>::f and B::f have different return types (long vs int),
and have different signatures. B::f does not hide A<int>::f, and both B::f and
A<int>::f are available for overload resolution.
Because they have the same parameters types, any call is ambiguous.</pre>
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