<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/112003>112003</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] unexpected statement kind UNREACHABLE executed at /root/llvm-project/clang/lib/AST/ItaniumMangle.cpp:4785!
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          yijan4845
      </td>
    </tr>
</table>

<pre>
    **This testcase is generated by a fuzzer.**

Compiler Explorer: [https://godbolt.org/z/EG7rrdfhb](https://godbolt.org/z/EG7rrdfhb)

This valid code for C++2c will crash on Clang Assertion Trunk:
```cpp
template <int I, auto...V>
decltype(V...[I]) foo() {}

void fn() {
    foo<0, 0>();
}
```

Stack dump:
```
unexpected statement kind
UNREACHABLE executed at /root/llvm-project/clang/lib/AST/ItaniumMangle.cpp:4785!
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++ -gdwarf-4 -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 -O3 <source>
1.      <eof> parser at end of file
2.      <source>:4:6: LLVM IR generation of declaration 'fn'
3.      <source>:4:6: Generating code for declaration 'fn'
4.      <source>:2:19: Mangling declaration 'foo'
 #0 0x0000000003ba44f8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ba44f8)
 #1 0x0000000003ba21bc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ba21bc)
 #2 0x0000000003aef418 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007c9eca042520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007c9eca0969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007c9eca042476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007c9eca0287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000000003afacea (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3afacea)
 #8 0x0000000007d47e64 (anonymous namespace)::CXXNameMangler::mangleExpression(clang::Expr const*, unsigned int, bool) ItaniumMangle.cpp:0:0
 #9 0x0000000007d39fe9 (anonymous namespace)::CXXNameMangler::mangleType(clang::QualType) ItaniumMangle.cpp:0:0
#10 0x0000000007d4d40e (anonymous namespace)::CXXNameMangler::mangleBareFunctionType(clang::FunctionProtoType const*, bool, clang::FunctionDecl const*) ItaniumMangle.cpp:0:0
#11 0x0000000007d4e561 (anonymous namespace)::CXXNameMangler::mangleFunctionEncoding(clang::GlobalDecl) ItaniumMangle.cpp:0:0
#12 0x0000000007d524ce (anonymous namespace)::ItaniumMangleContextImpl::mangleCXXName(clang::GlobalDecl, llvm::raw_ostream&) ItaniumMangle.cpp:0:0
#13 0x0000000007d774d3 clang::MangleContext::mangleName(clang::GlobalDecl, llvm::raw_ostream&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7d774d3)
#14 0x0000000003fa8784 getMangledNameImpl(clang::CodeGen::CodeGenModule&, clang::GlobalDecl, clang::NamedDecl const*, bool) CodeGenModule.cpp:0:0
#15 0x0000000003fba35d clang::CodeGen::CodeGenModule::getMangledName(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fba35d)
#16 0x0000000003ff1541 clang::CodeGen::CodeGenModule::GetAddrOfFunction(clang::GlobalDecl, llvm::Type*, bool, bool, clang::CodeGen::ForDefinition_t) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff1541)
#17 0x000000000435774e clang::CodeGen::CodeGenModule::getRawFunctionPointer(clang::GlobalDecl, llvm::Type*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x435774e)
#18 0x0000000004362e34 EmitDirectCallee(clang::CodeGen::CodeGenFunction&, clang::GlobalDecl) CGExpr.cpp:0:0
#19 0x00000000043841c9 clang::CodeGen::CodeGenFunction::EmitCallee(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43841c9)
#20 0x0000000004384177 clang::CodeGen::CodeGenFunction::EmitCallee(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4384177)
#21 0x00000000043847c3 clang::CodeGen::CodeGenFunction::EmitCallExpr(clang::CallExpr const*, clang::CodeGen::ReturnValueSlot, llvm::CallBase**) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43847c3)
#22 0x00000000043d7f34 (anonymous namespace)::ScalarExprEmitter::VisitCallExpr(clang::CallExpr const*) CGExprScalar.cpp:0:0
#23 0x00000000043cbddb clang::StmtVisitorBase<std::add_pointer, (anonymous namespace)::ScalarExprEmitter, llvm::Value*>::Visit(clang::Stmt*) CGExprScalar.cpp:0:0
#24 0x00000000043d1a7c clang::CodeGen::CodeGenFunction::EmitScalarExpr(clang::Expr const*, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43d1a7c)
#25 0x000000000435aabe clang::CodeGen::CodeGenFunction::EmitAnyExpr(clang::Expr const*, clang::CodeGen::AggValueSlot, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x435aabe)
#26 0x0000000004380e75 clang::CodeGen::CodeGenFunction::EmitIgnoredExpr(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4380e75)
#27 0x0000000003f06cc5 clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef<clang::Attr const*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f06cc5)
#28 0x0000000003f0e9c4 clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&, bool, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f0e9c4)
#29 0x0000000003f76e64 clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f76e64)
#30 0x0000000003f88e4c clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f88e4c)
#31 0x0000000003ff1a1a clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff1a1a)
#32 0x0000000003fec6f5 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fec6f5)
#33 0x0000000003feccab clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3feccab)
#34 0x0000000003ff7153 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#35 0x00000000044fefe6 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#36 0x00000000044efbc8 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44efbc8)
#37 0x0000000006631c24 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6631c24)
#38 0x00000000044fcb58 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44fcb58)
#39 0x00000000047b6459 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47b6459)
#40 0x0000000004734ffe clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4734ffe)
#41 0x000000000489bf4e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x489bf4e)
#42 0x0000000000cda85f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcda85f)
#43 0x0000000000cd256a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#44 0x0000000004540829 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
#45 0x0000000003aef8c4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3aef8c4)
#46 0x0000000004540e1f 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
#47 0x000000000450675d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x450675d)
#48 0x000000000450784d 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+++0x450784d)
#49 0x000000000450f175 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x450f175)
#50 0x0000000000cd772f clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd772f)
#51 0x0000000000ba7084 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xba7084)
#52 0x00007c9eca029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#53 0x00007c9eca029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#54 0x0000000000cd201e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd201e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
ASM generation compiler returned: 134
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkW11z4ygW_TXKC2WXhL4f8uAocSZT3TO9nWzvvLkQQrYmEqgApZ359VuAFAvFTuxsPLVb29XdFQO695zD5XKFCRKiWlNCLp3wygmvL1AnN4xfPld_IhokQXiRs-L50oELBy4eNpUAkgiJkSCgEmBNKOFIkgLkzwCBsvvrL8LnZrDjXjtu_3_GmraqCQc327ZmnHDHXwAnvNpI2QrHXzhw6cDlmhU5q-Wc8bUDl385cHlzG3NelJvcCa8dmBw_HKZj9xr3E6qrAmBWEFAyDjIHXjnwCmLws6prgDkSG8AoyGpE12AhBOGyYhQ88I4-Kp_GXuSav7htTYskTVsjSYDjZxWV4M6BGUCdZPP5_Ifj35hRBcG1fG6JA5Mf8_ncCa_uNKUUlIw5MFE_OfGVE1-PcT-xqgAlHfXrZgCAfszPXOXMVV70EMfvR-zsDHjHZu8lwo-g6Jr2NS_zsaNk2xKsJlZIJElDqASPFS1M9z9_-36zyH5ZXH25AWRLcKcGIgkcuOSMSQcu6_qpmbWc_Umw-oiVqKq5yh24XNw_OHB5JxGtuuYrouuazJWe_iKIk9CBnvHy7cvN4v4GiC5vKgkQyLs14KRlXALJwCQWKrnp8jlmTe_8NYZKiI4IBy4BogWoKK67ggC5If3c5wg_So4wUZq2nLScYSKEkoB13DSrJ5EQDFc66HlHgcC8auX8oLLu3HHTb5ytOWoA4utOaSl0_MMla7U6_eqYkWF19IrN0BCGYiZ1HMJlXtGdoCqCwWxd_ES8nAVgtgYzpuyitlXWO9l2ci7ArFFagNlsm0QzJJqZeKYSbR3_uqKS1GBWUjZ7Ijxngqh-MLsHs9ka45lkrMYbVFHHv34TrxosKGrFhkkwKzGrGZ8VFVpTJmSFhfGhlbabf_fVyuklHpaLp0Rz_Iyw0vFvQIu4IFxFGKEFYCUoq5qYkbAfuTPgLwLHX0RK4S9ffnwFd9-HNKWWMyuBWouo_-jAWK2v2Bjz3zJ22xuh610SOWwq2GMKOv7CS5UtHfTK0tSASga9BeBA3wXu1h3--DkKgjIBOrz9heMvxLMwP3zjFZU6-B5MBCe7QRz9XDEhOUGNAyMVxRWVOp-onPEpIejAK3fbw3tJvQq_N8EPvRzvw5_VBNGu_Z3eV2uKagcmHdXbUgFqprycA60CY6GFFlpEysBLQKZC9jvB7InwZwPvF0SLWjlNeiWtMRmjkmxln9Fc_e_Fhd-7iHFKMHIDGEK3p2Zy4zaJVlEwqyvabWdr2pkOPBdsHmng-hELdmDbTKO0xKCVG05QsXpUm9tJDvTzloNwCjqII7AWWotTwQdxZNmObNswiUsfoFwl-ZMs6wcty7E9myXCBH16FBmzlt9k7DcugphEgfKLKKPPDesEoKghotXrNO3j_48_fkMNMXshN22N_nCzbTkRomKqCjDuda9qB5hRIXW1lYGXBaNjMgM5Y7WKzX3b7CQoUxuxn5Yk_TjiB1PmjLD-o0O1aX0XjsoZ7kTAInDJx-FcIU6WHcVqOl9DG3q-cSaZ6rY0NRpmYM8D1wTXo7FHEfMmxEgYeR8nNiC5oZgVlQrLMbHbmuWoViiPBAdtcCEM8LuqW2b7vHfXtPUYZk_gMLoMHN6rjkLu28jjOCj88ZRZ8MbQ_hNcn5xIeti79xboe4GVwEqUxEkA1kQaPoVCr8W2GGSsILeEWh--sqKrSb_5H2Q76lCmi0mE7zKKZXX_lIQ29Bz5YQGOQ6mbbJZvRfZnJ3SD1ZqHyCZTemHgnULmlshFUfDfy2HFHhdzJllZeWhPPrKcLxm_JmVFK-VldZYiz9C39LE22sAP4zggJ072d_TzJRMz9U7CT9To04n2PCyiiU00gsQPwE1TyeuKEywzVNeEvL8cd2Hw1oJMQXarNvn9Cyy1oSSBh9P3NH_xawqIptqLeFJYnEFYDXYsLHRfsYnj_yE2cWyx8aZsYux_jI1CP4mnvtVKzIdsfyey4_QHqjtyXzNpLx1l6QoJ0h_WnUeaGFtbGoS2NEVc-u_WxvcY1Ygr0koWORRBPypxgkjDajLG9q4p6NvgcF4U-Vjbe9lI7ZVxLZyfCVmYLlQUq3ZIXNnpjKyZ0ROmUOtDg4GqTVFhOZpYMFHdQzE-PSB3qN95ExnqhE-PJw3ciqdwsvUglL-79bxmtqDPR9A6ZHaxXltL7Gz0NTuLfjTJNC6Jw9Pp360p46R4V4JzZAiF2KJkv7WXboTxByiZ5TFdMNZ07tbbgnP0_J2Ujp-NHlhIOSLv35ylmNL0LP7JhD9JcfCBzYM1LetooVj_q5Ib1sl7zKYvv-NRA9XomDrTDvlz6KJoW7qkti5xRKIP6DK0XLHi-c34OAMnDXnMaXK6WyYJCU7My_2ZNFGdx1XMu-LzzaSW3Q4D72jJRsFxBmE0b0sYb_rGhTx0yhuFmmojwO64ZngtOk4m0_6yE5_nRQp5yKJtnz-XBEflu7lvP-3_QrqajUXXn9LFKP8Y3b_1gEDjtIhMDmrK2AvfLfinRB5Y-4U8kR72mI5pGSZl3iIu5-5x5zC-XR8FJSlJ9O6JozGr8grju9M886XH2zBvOetatZPCFBhYV11VF2R_Xerb5UtAyhwnY92uEH4ktMgYFV0z1P2n4vjsmsXAtObfqlmiyPcwtPamb4gLor_0tnYc0qDJfnum0rGHZGFOJpGB8zDZE7OL8QZqvulfDGdYZ1FXA7GQ2kcdcR4FoXXUseSMSkKLPVDPBNJgGIMM7BOM2A_KcvIiYtzeUSERxWS_oodZnWXr7XFaROzDiyTNS_swr4e84_PEMHoN_xXf87xAGHwWAWsTdXGBkrAEGHurBikbyf66f4MmxX4G7DaYgSdWFefhYVBaNPwJDRhGCAziZ96DzhQjMvcNqusfBL_k7D2cosnhKWN1_62IVeAVvHo6kLID-yghDNwEplqYkd2yr7lWXGure4f7Sf2JBkZ1nSP8uCqp_dZlfPcxlHkZaxpEi-mi3juHL4cxrFXekdJgpI_kFV3rkTf9BL88sFrh7dbzzIcciQqvhB7eq2gNVg0ryVElxdA9MYfqWq0Jxkf9asjocEQHkdFcP-LAuEZNXiAHxjupYDJcfviV5fvnI5xeWUhwMD7k23MxoT8b7Og9Kkn9bMn59tSdoZoyiK3Ij6YhRrwS_D-HyKTsOxgL9vcwoRvF9pdulnB67tCrHXNQ00rmkwfVAOu44LihC6vYGXH71B3B0LYCKpnoEifBybr8ynJxWJRfWf6lEvYZylup-SUOWlRxc2_0FB37YPlb1FRiWWqmEzVLzz5zHCO_Hv1sFQ57KoZDs_A3qvn59YmRZ6xf6E429jiGfXobKpQBv04ri1fHlYe27U-vSRQyC7pVG7o5it0kAAr0Z_s2pi3fcHJPLC3SEy_O6Ucsm_7UJglcsFqpx1ZCIi5XI3JHeyGB7SWYVnKuR4Cx__lzpoy_eB93-wtAOGf64r1uB2X_hgFwvyJKVNWkAD8ruQFkW0lzzdUz39B1goDZE5AMCEJANSr7e2eL-6_je7YDG8D1l5BELVFla3Ld_KK49IvUT9EFufRimERhlKTwYnOZ4BKGPnYDL8xznIeoRJFXRrkbkiIiUXpRXUIXBp7reV4AEzeZIx-FQey5sAz8FEbYCVzSoKqeq6UzZ3x9oW-AX3oedF3_okY5qYX-rQcIe6WgE15f8Et9cTzv1sIJ3LoSUuxMyErW-lclzBPhNTh4VR6c-5b8Rcfry49fg-91eLqE_w4AAP__uTA_qA">