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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Arbitrary overload resolution on template function instead of "ambiguous overload" error"
href="https://llvm.org/bugs/show_bug.cgi?id=25669">25669</a>
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<th>Summary</th>
<td>Arbitrary overload resolution on template function instead of "ambiguous overload" error
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>3.7
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++11
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
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<th>Reporter</th>
<td>poletti.marco@gmail.com
</td>
</tr>
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The code below is a minimal code sample that exhibits the bug.
The type FindInMap<Map, int>::type should be `void' but Clang thinks it's
`char'.
This works correctly in GCC (tested version 4.8.5) but fails in Clang 3.7.0.
Explanation:
* The first overload of f (templated) is ambiguous (both Value=char and
Value=float match, with the same priority since both require a conversion from
Map* to the respective Pair<...>*) so it should be discarded.
* The second overload of f (non-templated) is the only one that remains and
therefore is the one that should be picked.
What's even more puzzling is that if the non-templated f is commented out, then
Clang displays the ambiguous overload error (which is correct) but for some
reason that's otherwise ignored.
template <typename T, typename U>
struct Pair {};
template <typename M, typename T>
struct FindInMap {
template <typename Value>
static Value f(Pair<T, Value>*);
static void f(void*);
using type = decltype(f((M*)0));
};
struct Map : public Pair<int, float>, Pair<int, char> {};
#include <functional> // Just for std::is_same
static_assert(std::is_same<FindInMap<Map, int>::type, void>::value, "");</pre>
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