<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/162485>162485</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] Assertion `UD.shadow_size() && "We shouldn't be codegening an invalid UsingEnumDecl" " containing no decls"' failed.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:codegen,
            crash
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          k-arrows
      </td>
    </tr>
</table>

<pre>
    Reproducer:
https://godbolt.org/z/o8a5rTb7v
```cpp
namespace foo {
enum class EnumOne {};
}
using foo::EnumOne;

template <class> void t() { using enum EnumOne; }
template void t<void>();
```

Backtrace:
```console
clang++: /root/llvm-project/llvm/tools/clang/lib/CodeGen/CGDebugInfo.cpp:6253: void clang::CodeGen::CGDebugInfo::EmitUsingEnumDecl(const clang::UsingEnumDecl&): Assertion `UD.shadow_size() && "We shouldn't be codegening an invalid UsingEnumDecl" " containing no decls"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang++ -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -g <source>
1.      <source>:7:24: current parser token ';'
2.      <source>:6:23: instantiating function definition 't<void>'
3.      <source>:6:23: LLVM IR generation of declaration 't'
4.      <source>:6:23: Generating code for declaration 't'
 #0 0x00000000041d1278 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x41d1278)
 #1 0x00000000041ce6a4 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x41ce6a4)
 #2 0x0000000004112ff8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007f7d87842520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007f7d878969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007f7d87842476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007f7d878287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007f7d8782871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007f7d87839e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x00000000044f63d1 (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44f63d1)
#10 0x00000000046b0bec clang::CodeGen::CodeGenFunction::EmitDeclStmt(clang::DeclStmt const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x46b0bec)
#11 0x00000000046c6feb clang::CodeGen::CodeGenFunction::EmitSimpleStmt(clang::Stmt const*, llvm::ArrayRef<clang::Attr const*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x46c6feb)
#12 0x00000000046be671 clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef<clang::Attr const*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x46be671)
#13 0x00000000046c697c clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&, bool, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x46c697c)
#14 0x000000000472efce clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x472efce)
#15 0x0000000004740fe4 clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4740fe4)
#16 0x00000000047add90 clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47add90)
#17 0x00000000047a8c74 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47a8c74)
#18 0x00000000047a9b10 clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47a9b10)
#19 0x00000000047b42e3 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#20 0x0000000004b18859 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#21 0x0000000004b07984 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4b07984)
#22 0x0000000007498d6a clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7498d6a)
#23 0x00000000072d29f2 clang::Sema::ActOnExplicitInstantiation(clang::Scope*, clang::SourceLocation, clang::SourceLocation, clang::Declarator&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x72d29f2)
#24 0x00000000068f3d6d clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x68f3d6d)
#25 0x00000000069013f9 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x69013f9)
#26 0x00000000069d1188 clang::Parser::ParseDeclarationAfterTemplate(clang::DeclaratorContext, clang::Parser::ParsedTemplateInfo&, clang::ParsingDeclRAIIObject&, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x69d1188)
#27 0x00000000069d1cdc clang::Parser::ParseExplicitInstantiation(clang::DeclaratorContext, clang::SourceLocation, clang::SourceLocation, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x69d1cdc)
#28 0x00000000069de848 clang::Parser::ParseDeclarationStartingWithTemplate(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x69de848)
#29 0x000000000690a700 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x690a700)
#30 0x00000000068c6df7 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x68c6df7)
#31 0x00000000068c7cc5 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x68c7cc5)
#32 0x00000000068a932a clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x68a932a)
#33 0x0000000004b14258 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4b14258)
#34 0x0000000004dffe65 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4dffe65)
#35 0x0000000004d81abe clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4d81abe)
#36 0x0000000004ef700d clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4ef700d)
#37 0x0000000000dbe180 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdbe180)
#38 0x0000000000db4cea ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>) driver.cpp:0:0
#39 0x0000000000db4e6d int llvm::function_ref<int (llvm::SmallVectorImpl<char const*>&)>::callback_fn<clang_main(int, char**, llvm::ToolContext const&)::'lambda'(llvm::SmallVectorImpl<char const*>&)>(long, llvm::SmallVectorImpl<char const*>&) driver.cpp:0:0
#40 0x0000000004b7d409 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#41 0x0000000004113494 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4113494)
#42 0x0000000004b7da1f clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (.part.0) Job.cpp:0:0
#43 0x0000000004b3ed22 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4b3ed22)
#44 0x0000000004b3fcce clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4b3fcce)
#45 0x0000000004b47405 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4b47405)
#46 0x0000000000dba6a9 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdba6a9)
#47 0x0000000000c6ab74 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc6ab74)
#48 0x00007f7d87829d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#49 0x00007f7d87829e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#50 0x0000000000db4785 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdb4785)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134
```
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzkW11z4yiz_jXKDeWUhGR9XORCceI52ZqtmYpndy9dCJDDiQQ6gDLJ_vpTgBwsxU7ivPHUbr1bszWygKafp5umaTFIKbbhlF4E88tgfnWGen0n5MX9DEkpfqqzSpCni1vaSUF6TGUQl0FY3mndKfMIlwFcbgSpRKPPhdwEcPl3AJciR3P5o8oegrAM0tD9wV0XhCVHLVUdwhTUQoAguwzCkvK-BbhBSoFr3rffOLUN2VUQm2bzEJa9YnxjBpl543LoOPQIS03brkGagiBeWFFBfA0eBCNABzAPYGFEAifEzucFADfBs4RhVLwwD0F87cYPM23RuFkvEb7XEmHqePFYBVeioUFY4gbxTQAvzZ-4BAFcSiF0AJdN89DOOin-l-LtzwAutRCNCuByGLZsWBXA5UIQ-oVy8_Tlilb95obX4twQGpcpnMdGstXaDbMEbce4H37YQF_L9B-GDEPDFcVNAHOjtN4VMemQWhZKUCpFpWaCgyAN_7g6V3eIiJ9rxf6mW6pN3xQEEP5FgboTfUN4ADMNKgqwIHRDubED4oDxB9QwAiZTQTMWYME1YrYrF4BQbKiBAcxAjVhDyXkQlt-_Xpera6D6qmUaIFD1GyBpJ6QGWoCJozJ911fnWLSe8IkZmFI9NQYAiBPAOG56QoG-owBLpO5A9WxwuACdNOsCU6UoAUr00r02I5FSAjOkKQGy50BhyTpt9F1phO8B6dvOuUx4HoTFdyk2ErUAyU3fUq7V4CqiMzph0XasoXJGH7tGSCq3_jFDW0uomZY9vw_gsmLcu4_xOjDbgJkw0lDXGZm97np9rsCsNdjBbPaYpzOk2pl64ho9BvEV45o2YFZzMXugshKKmnYwW4HZbIPxzDgpvkOMB_HVq1qazoqjTt0JDWY1Fo2QM8LQhgulGVZuDsvs-PXGLOOB0fg6CMvI0DR6F5dZEJcwMVThXkrKNeiQVFQCLe4pBwHMzJqFWRCWcM_w1Ay3S4dxpRHXDGkbYnqOrXcTWjPOnKPDbBQQjMz4VZlfv_75O7i5BRvKqURWiKitD6Php5VpJSWvSvoySOAbu3ZALeQBOSCAcQjCx3D7XxKRCGY5sL5ul7R6Uu7hu2RcW2f84dw5950k-rkWSkuKWruSF4Bx7dZ1_kleGcDL8HFQz4QVp3w0Vh7TFCX7lF80FPG--8ZXbMORiV09t9sYAY0wU5xAVauMVxWOVY1gXedgYTz5lmLxQOWT0-1_ECeNmTEfOBz1WQiu6aMeQnlo_3fy40F-Vmckz_IEzmE4gHJ7wmOertNk1jDeP842vHcN-FyJ89SpbIZ4hZOxwCItagw6fScpIut71jTHSbfjvfT5VN0kS8FGWQqOVTvJUi84HQuGeVbHAFUmvh8l1g70YrMXYqPqaIFR5QXmY4FxQYv0OIF2iBdYjBwsqdOYRJ_u1U6sm9Ssv3H0SKuwovhwUuF-LId46RMLs4evdGsSr52x27fA5hkunfh0QE5lD2gcUVKc1rQ6HtCKtV1DX0LahVOaOOljVSklerqltUtHtwNKraUfYHaSE1BgQXoK4MSmNM2iD1DwLwFv4Xnw8dT-RfYBh16IthM9JwbyX0zfiV6vsOjomJDdXjtOvgCVEI35-9C85WbzJ2p6umrESbZZB9uTkoxIySCtMT2elO2bS0GeXvWMzwfkVPaA5mNASVjT5DhAQ5JFTeMYzJdGVKhxx5JdH38e75z_8Mlr29Ecvk4a-xxuz0o6ZgURUoRvsfK7IH1DvZEd-i2Eq-eM-H0cuffWt0_lCRaVx5xNMOc4e9MT9mP-J2I1aDzWfIK1qKIP2vcwwlOgMHp6FOM8J6sSSONjUfwQ3Vf6QJttIWOcdHhznHdI6vPQpuG7kib5t0nvx5lQFeX53IpAXPCnVvQKPFeyXFnEa2cCiZA3bde41-4I8LqOX6ToO7NjwgI4nS571hAq96g2zmmqMCvykY9fInxPOVkIrvrWleyOV-Kzze7UfDY7HGUlWVLkJEW7IFa0Re7p5vl0Tt-KQyt7gP4qMHJto7DsBw8u4Tfm8d-fDn6A58GPspIMEljUcD_4Eutv_Pqxaxhm2jPxErlLR6Zb0auEvNp4NVQYhDzNbjWg9pyMkpI0r2OSjuqZ321tZ-f5ytdAylpT6TUuOTG5Jqt6TdVLN9-BtXh1BvJjKAlPtu6Do5ZC3iK-oTecnSj1GYjxtI1Sn7QIo7gu3qTNLvQxMaaN8Y09pHXmBDXF6Zkbihb7eBjxfhy_L_tP_XPq3L-YecetZz4dM0-iKM-Pctgt-kMe-grPR7C4Y9jb8ubmW-Uq3W-Rvdd4r5q3xJgqZZyH1cwwfAITWJK9CbKpCTDBr3L1jkj6Fv8fD6n_Foox8WdFmE8opnnybi9faSQ14xtzZP6Ys3-IslOQYmB7UopJ0EVZGL6XlF9AwJE99sTZU0RPQ9IzhePvFGmOU1JnbyxdTSV355K9VH4GFS92wdPs4Rat5yKacJFhPH-Vi8Np_LcO_V9Pv2s5Lr2Nsvv4eo8PPGec7vRx03ZC6pW2K_Yka8rB9CTAMQmoiCF6QUK5-jHJe43e4yrbiZL4QSWvcDw5ISZwnu85uJa7ZbNHintNh1fbb-WffNCying1x8U-Utc0HTnXUprAw8kePU-kodPBaziu3pE8QtWkHOnmdJs2pvu5PAzpNNU2p6dHMa620ToLw9H5ZdDXg3l4DrjTIvII7GlqSU4_r_0okwpJRaM8BBhH6xYZAfn-2v4dmhT0F2D8Di7svZTTgHBaegz5BEOCKQJb2hfRDxsXdpCsWtQ0f1L8XKzZAygdF_mMjGGjHp0HfY8brmWv2AO9pfWCaxeJffNDPXzCXrKGrp6Upu3wJYRI9rCv3DP-EGhg0ZQAxvXOpNsrC2tp7WIaP4K0cFcPgrjEqGkqhO_XNd9uJFtPsJ-xnZ2tWcv3MDQUyAKYNaitCApg9mEFYe6-8e_O-t7xB1lOJvW-jCRh4e5UHaTZtm4vhx0mzjW4iYc1vogWom0RJ9Nwu3eZKT30E52ZHTUjj1ppyfhm2NfdGnwesF7jx8cocj8qpBheK9t9IGjU2bxYa4mYVtvmiTjUNCZmCbnTbrrs1NLsOne077P4xIQF-E1Ue4wxuQcSxUmxew9k3xUK13Lb8xWqafM04vJ1u53isojV-DkyJXDqXCiqwX-zc0yK8fu9YJJgxZRAeJA1azX0IoXZUjnaYycDTYdD1b1XupajvHMH2Oemcxa2d6VkQkqNx99u30PKb6JShxn5TVRfmTq0v72MtM8e0CEm3e5zDImDm_wSKg1Znspx3lklWRLOD6l9tfM8yuT2pHCHTPALqTzBscLS48lLJ1kJStFQd_7PEoXPTxKNZl7vcaKLU1RlCTAaf_bETrSfeHJBDBakOPJCnx3iBRZTgTQJwXptxqyVRlKvd2C9ewqa-Cnm4TT1zPI5cMI_305GuJt6ty0uAZXS7Cqlcy9QD6c7gAf_d5fBwU-m7wB9ZNpdk43ixOjYKwpmD0ALoCgFbOfUZWbanraApLqXnJrlZ0bu3uU_IxcxKeICndGLKJsXRQzjMDq7u6goSeqakDDDNCRREiIcZTXN8ijOoriAZ-wChnAehWEeJWEyj8_jIglDUmcRpUVCsyRIQtoi1pybZXEu5ObM3j-_iFKY5POzBlW0UfZfZkC4DQLD_Xl7EX5h3ptkyPyaX53JC3udveo3KkjChimtvGjNdGP_mYeTNL_6B13kP-tlc_Hxy_oDXw8X8P8DAAD___a0rbY">