<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/150733>150733</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] crash on invalid  in C++11 mode
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            c++11,
            crash-on-invalid
      </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/6qfnP5jfe
```cpp
auto L = [](auto a) {
  auto M = [](decltype(a)) -> {
 };
};
```

Backtrace:
```console
unexpected statement kind
UNREACHABLE executed at /root/llvm-project/llvm/tools/clang/lib/AST/ItaniumMangle.cpp:5000!
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 -std=c++11 <source>
1.      <source>:2:31: current parser token '{'
2.      <source>:1:10: lambda expression parsing
3.      <source>:1:21: in compound statement ('{}')
4.      <source>:2:12: lambda expression parsing
 #0 0x0000000003fd9768 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fd9768)
 #1 0x0000000003fd6b94 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fd6b94)
 #2 0x0000000003f1b388 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007b7078042520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007b70780969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007b7078042476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007b70780287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000000003f26b4a (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f26b4a)
 #8 0x0000000007b6e2bc (anonymous namespace)::CXXNameMangler::mangleExpression(clang::Expr const*, unsigned int, bool) ItaniumMangle.cpp:0:0
 #9 0x0000000007b65b70 (anonymous namespace)::CXXNameMangler::mangleType(clang::QualType) ItaniumMangle.cpp:0:0
#10 0x0000000007b72dde (anonymous namespace)::CXXNameMangler::mangleBareFunctionType(clang::FunctionProtoType const*, bool, clang::FunctionDecl const*) ItaniumMangle.cpp:0:0
#11 0x0000000007b7ee0e (anonymous namespace)::ItaniumMangleContextImpl::mangleLambdaSig(clang::CXXRecordDecl const*, llvm::raw_ostream&) ItaniumMangle.cpp:0:0
#12 0x0000000007b560e9 (anonymous namespace)::ItaniumNumberingContext::getManglingNumber(clang::CXXMethodDecl const*) ItaniumCXXABI.cpp:0:0
#13 0x0000000006d2e145 clang::Sema::handleLambdaNumbering(clang::CXXRecordDecl*, clang::CXXMethodDecl*, std::optional<clang::CXXRecordDecl::LambdaNumbering>) (.part.0) SemaLambda.cpp:0:0
#14 0x0000000006d336b6 clang::Sema::ActOnStartOfLambdaDefinition(clang::LambdaIntroducer&, clang::Declarator&, clang::DeclSpec const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6d336b6)
#15 0x000000000671d0b8 clang::Parser::ParseLambdaExpressionAfterIntroducer(clang::LambdaIntroducer&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x671d0b8)
#16 0x000000000671e48b clang::Parser::ParseLambdaExpression() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x671e48b)
#17 0x00000000066fee15 clang::Parser::ParseCastExpression(clang::CastParseKind, bool, bool&, clang::TypoCorrectionTypeBehavior, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66fee15)
#18 0x00000000066ff7d7 clang::Parser::ParseCastExpression(clang::CastParseKind, bool, clang::TypoCorrectionTypeBehavior, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66ff7d7)
#19 0x00000000066ff869 clang::Parser::ParseAssignmentExpression(clang::TypoCorrectionTypeBehavior) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66ff869)
#20 0x00000000066b8088 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b8088)
#21 0x00000000066c6919 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+++0x66c6919)
#22 0x00000000066cf527 clang::Parser::ParseSimpleDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, bool, clang::Parser::ForRangeInit*, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66cf527)
#23 0x00000000066cf9e9 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66cf9e9)
#24 0x00000000067907d2 clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 24u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::ParsedAttributes&, clang::ParsedAttributes&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x67907d2)
#25 0x00000000067914a9 clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 24u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x67914a9)
#26 0x00000000067995db clang::Parser::ParseCompoundStatementBody(bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x67995db)
#27 0x000000000671d3a2 clang::Parser::ParseLambdaExpressionAfterIntroducer(clang::LambdaIntroducer&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x671d3a2)
#28 0x000000000671e48b clang::Parser::ParseLambdaExpression() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x671e48b)
#29 0x00000000066fee15 clang::Parser::ParseCastExpression(clang::CastParseKind, bool, bool&, clang::TypoCorrectionTypeBehavior, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66fee15)
#30 0x00000000066ff7d7 clang::Parser::ParseCastExpression(clang::CastParseKind, bool, clang::TypoCorrectionTypeBehavior, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66ff7d7)
#31 0x00000000066ff869 clang::Parser::ParseAssignmentExpression(clang::TypoCorrectionTypeBehavior) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66ff869)
#32 0x00000000066b8088 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b8088)
#33 0x00000000066c6919 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+++0x66c6919)
#34 0x000000000668430e clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x668430e)
#35 0x0000000006684a9f clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6684a9f)
#36 0x000000000668c7aa clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x668c7aa)
#37 0x000000000668d735 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x668d735)
#38 0x000000000668dbf0 clang::Parser::ParseFirstTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x668dbf0)
#39 0x000000000667f473 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x667f473)
#40 0x0000000004985888 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4985888)
#41 0x0000000004c78555 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4c78555)
#42 0x0000000004bf538e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4bf538e)
#43 0x0000000004d6c281 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4d6c281)
#44 0x0000000000daa6bf cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdaa6bf)
#45 0x0000000000da130a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#46 0x00000000049ec839 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
#47 0x0000000003f1b824 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f1b824)
#48 0x00000000049ece4f 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
#49 0x00000000049af47d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x49af47d)
#50 0x00000000049b050e 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+++0x49b050e)
#51 0x00000000049b8545 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x49b8545)
#52 0x0000000000da6b6f clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda6b6f)
#53 0x0000000000c5b964 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc5b964)
#54 0x00007b7078029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#55 0x00007b7078029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#56 0x0000000000da0db5 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda0db5)
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/eJzsm1tz27a2xz8N_IKRBwTvD36gZat1T9L4RD5n8qYBSVBiTQIsADry_vR7AFDixZIcZ6zs7F6mndLE7b9-WFxYoEAiZblmlF4B_xr4NxekVRsurh5nRAj-VV6kPH---kwbwfM2owK4CUDJRqlG6ku8AHix5nnKK3XJxRrgxb8AXgR_Fuze_6OgACUgQPbfrGkASkirOPwAgXsD7YgAR-YeATiGILwGKIHQ3Pk4rpXTrFLPDdUNAI519Rlwb3dtQHgDXH3VX-xG1tcouSbZoxIko9aGXhdnkldaasvotqGZojmUiihaU6bgY8lygJL_-_3zbTL_Nbn-cAvplmatrkUUBHghOFcAL6rqqZ41gv9Bs92fAC8U55UEeJFVhGk8VZkCvEiWDwAv7hRhZVt_JGxd0UvNx018hBDADkDJ_YfbZHkLZZvWpYIEpu0aCtpwoaDicDIFpdq06WXG637kiZ5SypZqJZCwHJYsq9qcQrWhMBNEbmC6x4PnsBF6xjMqpWbBW2Fv65ZESp6VRJsvWgZlJspGXQKULBXJHmHe1o0FjC4Biu8FXwtSQyLWrcapJWtmvNGaMl43ZUXFjG6bigsqdqBmREoqVMmZnCnRskeAF2nJeo7XAF_D2Tr_SkQx8-BsDWdc90uaRvfeqqZVlxLOak0BzmbbKJgRWc_kM1NkC9ybkilawVnB-OyJipRLqsvhbAlns3WWzfS8ZRtSMuDenNSrK0tGGrnhCs6KjFdczPKSrBmXqsykHcMwHt-WKgfuTWZtcRwI3HlH2r0FKHE0vtE9N8HATVxHI8xaIbR3NkRIKqDij5RBgEP9MOAQoAQfaK5bOkg3r0id5gTSbSOolCVnpqOSrQFK3CMtsRm4ZFBT4C0bPiQAR93g4Y2-wDFAiXfEAge_JgEC7CKItmj3j1vkcRhE0Li2mwA3kc_SXtyLkinjew_We6O-kiBfV1wqQUkNcKA9uGTKxBmt912cEOBrtO3kWbO1eGciPkhj75D4eUUJa5tPbFmuGakAjlpm4nEOK66HOIdULaaXisdSndSNIjjX7vqZZvyJimer7VfC8kqPGHUMR3XmnCm6VV0QQ-Y_27_b9R-mIQoj5GEfo84oGwu3UbAKvFlVsnY7W7PWFmSXkl8GRrJp0gv2xh3GQVxksFEbQUm-eiyr6m29m_Z97_5UrhcGcC0NgrfK9sKg7zgYd4yjsHAhSXU4f1O3pmHfbTiePhykHnl_nzHd9oNGw0HDNKA4zfSghHH2XPNWQkZqKhvzPMadq3_58jupqV3shL1Xmz9u9yEA4MiObUr1fahXZwVwoh_e_bNhPHAOU84r7YmH1tGhC8YTuX4aou-X-2BzkIHQ_21JZe-e1qIDAxprCXGe0-_Xck0EXbQs07P4Uteu5F5wxXXxiKalN4cHGtzQrBrUfd0qZ2IVpehVq0Z9dvHjrm6qoX0fzCKxLNdjw-ZfvujAI_KJ0Dk8HvtfNwKPjfADRONvNOL3tk6pKNm6s8MWrqkyg5VsbSu8sOIjVRs-tWKvdP7lS3J9d0CpO1Qa5Jg6nj-cxyWtib3amKhtMe5FnoDZYTymsis2qYsu5I12F1IBd360R3NrqsC97da2y4YIdanDO9Sqbb0DJntjk103SIPDJieZ-sSWigj1qbDd3dCiZKV6EWBs6R1Tu82NzREGNbQBRBDFj5QtG5rtZi44w2rdGWojr8bgjzCETo7SaCjq3uSDg2trYx9ik0JRMTT5VSDvb5SV3RsVTIyiXpS-ySgj8Bw6tZJe52itDYKCUsc_qXNOpDq2uukyU-l_9AZzEI_t_6fe9vDc8DkXgu5j_TXdkKdSe-a0bXIOGNbcHkY0gVGEefj-MH4uAtrGnkA8JRAF8UkCiXnXojdMxzicsvEsBkVBvDcIo7FBaYSi08FlFx53caUPlwnLE6VEmbaKyrGNp2LqixHyB1o3FVH0jhV8EGmPtlpw8ZmwNb1jpTqXHxgwPTZnjC0LYue0H2gCvwjeNmMw93b_u1tXTq1GuzTjAIcR97fxfVl_abbuH3hG7Oo5TQ5-NHnDtiePJ-QLH5-OQcuybqqh2x5zzcOApzgO4n19Al7WOBDuTqJ9bZLOgV7D7dG7U_Qxfd3pfy7o_wGEMR147zilDWMU5vi09-7et30S08g7Crb9JmhZk6r6f5rpYDtK0Zeq3nkS9lqTjr8eK3Sjb5ujg3Hi7XN0hpTOUO7nYJJPx45HTrvx4Tn4WaCfA5hG0gOb5Opx7Oenc_V597Z4D-6a588AR7uXN-8vWEvqBYfTHZNLTj9lP-mOySUDt43-O3ZMeJoi_513TC76u--YXOcvtmNy8T87pu_YMbnT5PGfHdMP2jG545wziDwX0VfJfxL9DwPFHVNU2N8q3zkJf3U2kyyjUuqysijpeR5wQ6Tn5U95kbj41gd8hO3gC-izUJt63I-hRuKipxZMqGUhISep3W6tUx3dJJ6L1DlYaGt7FpOXxlEeuqdToAfefKBPtLK_twwhfGrIny29V5NtxT44fqbFwU1F_9vIR563Fb2rGy6UScjPlK9aM3sI0RRCWqCTEBalkOovQiItUE9ikhGHhRe6L0iY42HRVPf4VdG59k9W0l6wN8pavTjyo3GKM-c5_YWyxAQ6e-vWno_rbp1lp9EJ6WWOUksvCyPfHz1mC6ETAJYf0HkmhVZDr3CUK3pp4bsRHYO0Y94xqQizxxRfsjxu0ln8t9PZWzFK3bw8yHDkDK3o9PbGPO1ToeiUsWcJxp2-Xv0o_UE5IUFawCxzVjUpxy9xEiHIswkj82xDBudQdFiZw_E9PIdPvMzPY4RV2dvgT2xwXETgDvvceTBx4fDrKHu84oBBwfjshO6jS5hHv27nonyi4uWv814wDhI0i9zYIBl0WnTJ0EoYqqbUPnr2aCBwk4xUVUqyx1XBxoHdDty5ztyZ87omLJ8-xQdn79BZhQEcJUq27pYLO7X7BqtVtt06jv0jJbLMVlLZ0wsG4aiyvrFSgpRK7oon3ZGq0o-CfSnYlesqyWQTboGbJgCH9pikOVO5Q4Wj3dnA33h6YDLC6Ym-CA8PHx46t2dLPrdsSQpaPY9Ynp63c5xQNIp7h4-mzkW9UQ7-t3OOybmZw14Qj6mRwgvzo9TMrJEXK-MO5Sh0TxrqCsdeM5yomozSmYFh75slGLP3ruRPkpkU-ePt77dA-Y2n8jiR33j6oZRqRORULN57QENKPfnd0cZvhdi5yY9AaWD1KJ0Jysgfn0Ebyr4ZXI8ShAOZwbEp-IEoz5CtGjw9PDxZw4M06ELaLhPZiTehJHlxuvHYCv3uuYdW1useZX8o89M48KBW_N4D2677gSeHvnGcx288RW6a9B360w6ph-BqpduspCJCrQZmffMQ1BsMEUwmGeWpD23n7z9PunM79LDMTSAVQq8qiXUvWHSbBph1_l-QsqI5_FqqDaTbUrtTTqHjelpjKymcPUHFoaQUloNkXo-0S-KhoKoVjOrHT7ccfl11kV-5eezG5IJeOaHverEfoOBic4Uyn4YBpiiPigJRHKdpjmgYhl6QIpp6F-UVRthHIQ4QRoEXXPpx4MYhLryocIIs9YGHaE3K6lI_FpdcrC_MN05Xjo9C172oSEorab5rw3j_mQ3AGOC5vmO-yOFsVrInUunkHQP_5kJcme-m0nYtgYeqUirZ969KVZkv5Sxj_6b7dooz2PUCYcngfP9NT81zetGK6ur7P9fqrHm6wv8OAAD__27MPrw">