<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/120033>120033</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Compilation Hang Issue with Deeply Nested Template Instantiation in LLVM-18 and Trunk
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          iamanonymouscs
      </td>
    </tr>
</table>

<pre>
    This hang can be observed in both LLVM 18 and LLVM trunk versions.[https://godbolt.org/z/dKPhr395q](https://godbolt.org/z/dKPhr395q)

# Command 
`clang++ bug.C`

# Code
```cpp
template<template<int N, int M> class>
struct A;

template<class U>
struct B {
  template<class T>
 struct C {
    template<template<auto X, auto Y> class TT>
    using type = A<TT>;
  };
};

template struct B<>;

template<class U>
struct C {
 template<class T>
  struct D : C<typename B<T>::template C<T>::type<int>::template C<T>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type<int>::type>::C<int>;
```
# Version
`clang++ --version`
```sh
Ubuntu clang version 18.1.8 (++20240731025011+3b5b5c1ec4a3-1~exp1~20240731145104.143)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
```

</pre>
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