<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/94928>94928</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            `-ast-dump-decl-types` crashes on codes involving concepts 
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            c++20,
            clang:frontend,
            concepts
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          zyn0217
      </td>
    </tr>
</table>

<pre>
    <details><summary>backtrace</summary>
<p>

```
clang++: /root/llvm-project/llvm/include/llvm/Support/Casting.h:662: decltype(auto) llvm::dyn_cast(From*) [with To = clang::ValueDecl; From = clang::Decl]: Assertion `detail::isPresent(Val) && "dyn_cast on a non-existent value"' failed.

 #0 0x0000000003a01968 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3a01968)
 #1 0x00000000039ff64c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x39ff64c)
 #2 0x0000000003948068 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007a2c9c642520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007a2c9c6969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007a2c9c642476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007a2c9c6287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007a2c9c62871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007a2c9c639e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x00000000045cb5a5 (anonymous namespace)::ASTPrinter::print(clang::Decl*) ASTConsumers.cpp:0:0
#10 0x00000000045cd6ef (anonymous namespace)::ASTPrinter::TraverseDecl(clang::Decl*) ASTConsumers.cpp:0:0
#11 0x00000000045cda6a clang::RecursiveASTVisitor<(anonymous namespace)::ASTPrinter>::TraverseDeclContextHelper(clang::DeclContext*) (.part.0) ASTConsumers.cpp:0:0
#12 0x00000000045d72f9 clang::RecursiveASTVisitor<(anonymous namespace)::ASTPrinter>::TraverseTranslationUnitDecl(clang::TranslationUnitDecl*) ASTConsumers.cpp:0:0
#13 0x00000000045cd670 (anonymous namespace)::ASTPrinter::TraverseDecl(clang::Decl*) ASTConsumers.cpp:0:0
#14 0x000000000635b0ac clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x635b0ac)
...
```

</p>
</details> 

Code:
```cpp
namespace ns {

template <typename T>
concept C = true;

} // namespace ns

using ns::C;

template <typename T> concept Foo = C<T>;

template <C... T, C auto U>
auto FooFunc(C auto V) -> C decltype(auto) {
  C auto W = V;
  return W;
}
```

Command line:
```
-std=c++20 -Xclang -ast-dump -Xclang -ast-dump-decl-types -Xclang -ast-dump-filter="Foo"
```

https://godbolt.org/z/ebcMq8b4e
</pre>
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