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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Failure to partially order constrained overload set of three parameters"
href="https://bugs.llvm.org/show_bug.cgi?id=44661">44661</a>
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<th>Summary</th>
<td>Failure to partially order constrained overload set of three parameters
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++2a
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david@doublewise.net
</td>
</tr>
<tr>
<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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<p>
<div>
<pre>Given the following code:
```
template<typename>
concept c1 = true;
template<typename, typename>
concept c2 = true;
template<
c1 T1,
c2<int> T2,
c1 T3
>
int f(T1, T2, T3);
template<
c1 T1,
c2<int> T2,
typename T3
>
int f(T1, T2, T3);
auto x = f(1, 2, 3);
```
Compiled with `clang++ -std=c++2a -o /dev/null -c main.cpp`
The expected behavior is to call the first overload. It is exactly as
constrained for the first two parameters for both overloads, but the first
overload has a constrained third parameter but the second overload has an
unconstrained third parameter. Instead, clang outputs:
```
main.cpp:21:10: error: call to 'f' is ambiguous
auto x = f(1, 2, 3);
^
main.cpp:12:5: note: candidate function [with T1 = int, T2 = int, T3 = int]
int f(T1, T2, T3);
^
main.cpp:19:5: note: candidate function [with T1 = int, T2 = int, T3 = int]
int f(T1, T2, T3);
^
1 error generated.
```</pre>
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