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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 - Partial ordering of function templates accepting template template parameters sensitive to existence of parameter list in requires expression"
href="https://bugs.llvm.org/show_bug.cgi?id=50577">50577</a>
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<th>Summary</th>
<td>Partial ordering of function templates accepting template template parameters sensitive to existence of parameter list in requires expression
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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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>davidfromonline@gmail.com
</td>
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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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<p>
<div>
<pre>The following translation unit is accepted by clang unless you define
AMBIGUOUS:
```
template<typename>
struct s {
};
#ifdef AMBIGUOUS
template<typename T>
concept true1 = requires(T) {
requires true;
};
#else
template<typename T>
concept true1 = requires {
requires true;
};
#endif
template<typename T>
concept true2 = requires {
requires true;
};
template<template<typename...> typename Template, typename T> requires
true1<Template<int>> and true2<T>
void f(T) {
}
template<template<typename, auto...> typename Template, typename T> requires
true1<Template<int>>
void f(T) {
}
void g() {
f<s>(0);
}
```
If AMBIGUOUS is defined, it is rejected with the error message
```
source>:35:2: error: call to 'f' is ambiguous
f<s>(0);
^~~~
<source>:27:6: note: candidate function [with Template = s, T = int]
void f(T) {
^
<source>:30:6: note: candidate function [with Template = s, T = int]
void f(T) {
^
1 error generated.
Compiler returned: 1
```
See it live: <a href="https://godbolt.org/z/6ecMWxcq6">https://godbolt.org/z/6ecMWxcq6</a></pre>
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