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      <base href="https://bugs.llvm.org/">
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Assertion failure in Parser.h:941: !isActive && "Forgot to call Commit or Revert!" when using concepts"
   href="https://bugs.llvm.org/show_bug.cgi?id=44822">44822</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Assertion failure in Parser.h:941: !isActive && "Forgot to call Commit or Revert!" when using concepts
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>10.0
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Windows NT
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++2a
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>curdeius@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=23105" name="attach_23105" title="run script">attachment 23105</a> <a href="attachment.cgi?id=23105&action=edit" title="run script">[details]</a></span>
run script

I get the following assertion failure in parser on Windows:

```
Assertion failed: !isActive && "Forgot to call Commit or Revert!", file
C:\src\llvm_package_1000-rc1\llvm-project\clang\include\clang/Parse/Parser.h,
line 941
```

It happens with this minimized snippet:
```
template <typename _Ty>
using iter_reference_t = decltype(*::std::declval<_Ty &>());

template <class _It> concept _Cpp17_input_iterator = requires(_It) {
  typename common_reference_t<iter_reference_t<_It> &&,
                              typename _It::value_type &>;
};
```

Initially run with clang-tidy (10.0.0-rc1):
```
clang-tidy bug-pre.cpp -checks=-*,readability-braces-around-statements -- 
-std=c++2a -x c++
```</pre>
        </div>
      </p>


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