<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/105885>105885</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Alias template with NTTP crashes if it has an unevaluated generic lambda taking `auto...`
        </td>
    </tr>

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

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

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

<pre>
    https://godbolt.org/z/rzdG81qd7

```c++
template<int>
using test = decltype([](auto...) {
}());
static_assert(__is_same(test<0>, void));
```

```
clang++: /root/llvm-project/clang/include/clang/AST/TemplateBase.h:439: unsigned int clang::TemplateArgument::pack_size() const: Assertion `getKind() == Pack' 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++ -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++2c <source>
1.      <source>:4:25: at annotation token
2.      <source>:2:23: instantiating function definition '(anonymous class)::operator()<>'
 #0 0x0000000003b07c88 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3b07c88)
 #1 0x0000000003b0597c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3b0597c)
 #2 0x0000000003a4e8f8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007558f8642520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007558f86969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007558f8642476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007558f86287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007558f862871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007558f8639e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x00000000072b00d3 clang::Sema::getNumArgumentsInExpansionFromUnexpanded(llvm::ArrayRef<std::pair<llvm::PointerUnion<clang::TemplateTypeParmType const*, clang::NamedDecl*>, clang::SourceLocation>>, clang::MultiLevelTemplateArgumentList const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x72b00d3)
#10 0x00000000072bf91d clang::Sema::getNumArgumentsInExpansion(clang::QualType, clang::MultiLevelTemplateArgumentList const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x72bf91d)
#11 0x000000000725333c clang::Sema::addInstantiatedParametersToScope(clang::FunctionDecl*, clang::FunctionDecl const*, clang::LocalInstantiationScope&, clang::MultiLevelTemplateArgumentList const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x725333c)
#12 0x00000000072a01ff clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x72a01ff)
#13 0x000000000669ff51 clang::Sema::runWithSufficientStackSpace(clang::SourceLocation, llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x669ff51)
#14 0x00000000070f4ba2 clang::Sema::DeduceReturnType(clang::FunctionDecl*, clang::SourceLocation, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x70f4ba2)
#15 0x0000000006ab9795 clang::Sema::DiagnoseUseOfDecl(clang::NamedDecl*, llvm::ArrayRef<clang::SourceLocation>, clang::ObjCInterfaceDecl const*, bool, bool, clang::ObjCInterfaceDecl*, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6ab9795)
#16 0x0000000006f3df97 CreateFunctionRefExpr(clang::Sema&, clang::FunctionDecl*, clang::NamedDecl*, clang::Expr const*, bool, clang::SourceLocation, clang::DeclarationNameLoc const&) SemaOverload.cpp:0:0
#17 0x0000000006f7cbaa clang::Sema::BuildCallToObjectOfClassType(clang::Scope*, clang::Expr*, clang::SourceLocation, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6f7cbaa)
#18 0x0000000006b2456d clang::Sema::BuildCallExpr(clang::Scope*, clang::Expr*, clang::SourceLocation, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation, clang::Expr*, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6b2456d)
#19 0x0000000006b2658c clang::Sema::ActOnCallExpr(clang::Scope*, clang::Expr*, clang::SourceLocation, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation, clang::Expr*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6b2658c)
#20 0x000000000720cb70 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCallExpr(clang::CallExpr*) SemaTemplateInstantiate.cpp:0:0
#21 0x0000000007200485 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#22 0x00000000072112bd clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformType(clang::TypeLocBuilder&, clang::TypeLoc) SemaTemplateInstantiate.cpp:0:0
#23 0x0000000007217cca clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformType(clang::TypeSourceInfo*) SemaTemplateInstantiate.cpp:0:0
#24 0x0000000007217dec clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformType(clang::QualType) SemaTemplateInstantiate.cpp:0:0
#25 0x0000000007219aab clang::Sema::SubstType(clang::QualType, clang::MultiLevelTemplateArgumentList const&, clang::SourceLocation, clang::DeclarationName) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7219aab)
#26 0x0000000007053216 clang::Sema::CheckTemplateIdType(clang::TemplateName, clang::SourceLocation, clang::TemplateArgumentListInfo&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7053216)
#27 0x00000000070555d7 clang::Sema::ActOnTemplateIdType(clang::Scope*, clang::CXXScopeSpec&, clang::SourceLocation, clang::OpaquePtr<clang::TemplateName>, clang::IdentifierInfo const*, clang::SourceLocation, clang::SourceLocation, llvm::MutableArrayRef<clang::ParsedTemplateArgument>, clang::SourceLocation, bool, bool, clang::ImplicitTypenameContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x70555d7)
#28 0x000000000663967b clang::Parser::AnnotateTemplateIdTokenAsType(clang::CXXScopeSpec&, clang::ImplicitTypenameContext, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x663967b)
#29 0x0000000006574710 clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6574710)
#30 0x0000000006577492 clang::Parser::ParseSpecifierQualifierList(clang::DeclSpec&, clang::ImplicitTypenameContext, clang::AccessSpecifier, clang::Parser::DeclSpecContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6577492)
#31 0x000000000657e470 clang::Parser::ParseTypeName(clang::SourceRange*, clang::DeclaratorContext, clang::AccessSpecifier, clang::Decl**, clang::ParsedAttributes*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x657e470)
#32 0x00000000065b7324 clang::Parser::ParseTypeTrait() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65b7324)
#33 0x00000000065a6f7d clang::Parser::ParseCastExpression(clang::Parser::CastParseKind, bool, bool&, clang::Parser::TypeCastState, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65a6f7d)
#34 0x00000000065b4c7e clang::Parser::ParseConstantExpressionInExprEvalContext(clang::Parser::TypeCastState) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65b4c7e)
#35 0x000000000658c114 clang::Parser::ParseStaticAssertDeclaration(clang::SourceLocation&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x658c114)
#36 0x000000000657ad09 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x657ad09)
#37 0x0000000006537c31 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6537c31)
#38 0x0000000006538abd clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6538abd)
#39 0x000000000652bf5a clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x652bf5a)
#40 0x0000000004424038 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4424038)
#41 0x00000000046b2fb9 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x46b2fb9)
#42 0x000000000463678e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x463678e)
#43 0x000000000479c6be clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x479c6be)
#44 0x0000000000ca698f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xca698f)
#45 0x0000000000c9fbda ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#46 0x00000000044676f9 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 0x0000000003a4eda4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3a4eda4)
#48 0x0000000004467cef 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 0x000000000442d885 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x442d885)
#50 0x000000000442e2ed 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+++0x442e2ed)
#51 0x0000000004435f05 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4435f05)
#52 0x0000000000ca3d85 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xca3d85)
#53 0x0000000000b780e4 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xb780e4)
#54 0x00007558f8629d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#55 0x00007558f8629e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#56 0x0000000000c9f68e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc9f68e)
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkW19z4ygS_zTKC2WXjP4_5MHjJHvZy2xy4-zdvrkQIJuNDFpAmWQ__RVItoUse5KpaHavbsuzsSVo-vfrprtBCCnF1pzSSy_65EVXF6jWGyEvPzONyrnaiKeLXJDXy43WlfKCuQdvPHizFiQXpZ4KufbgzZ8evJF_kp_S2R8k8fwrz5-3_4_95oM9-Ml87FVNt1WJNPWCBePaC66by7VifA00VRp4wRUgFJf6taIeTBvNPJiiWovpdOrBDHhJK81LzB0PZuYTtBeVRprhFVKKSu3BdLViaqXQ1kgzI3jBwjcDwwV4Foz0eu_VHsTS_MQl4usWVTAHhgEhtAdvyvJ5O6mk-J1i87Ntd8M4LmtCO1fmy0cP3jy2ZHxCik43XjAPg8wIrLk1CwGMa9B0CeZeMN-1n8t1vaWGPnO1QvhppdiftKECYMENyDmYWwaY4MCL_TXV_2SctG284Mrw_IDwkwcTUCBWUjJt0D3cXc-X10DV-ZZpgEBer4GklZAaaAF6vsD0ps6nWGxb9MckMKVqqjx4AxA3iCwVQG8owBKpDcgRftISYWoMUklaSYGpUpQAJWrZXDY9kVICM6QpAbLmQGHJKt2qvNQIPwFSbyujmb3kTz0_e5BiLdEWoJYw1ZpLVNY8YluxksoJfalKIancGWiCdsypiZY1f_LgTc74wX7G8mCyJl-RLCYhmKzBRBi5qKqM9FpXtZ4qMNkaLsBk8pLGE6S2E_XKNXrxgivGNS3BpOBi8kxlLhQ198FkCSaTNcYTLUSJN4hxY6hz-prGiqNKbYQGkwKLUsgJYWjNhdIMq2YMy7R7WWniBVft3IQYeMGi5Xs3J2eGQedyMA-9YA4jwyLSAHEuzFwTHGjxRHnTDQ50g-ZfYLoxrjTimiFtJnxRc2z7E1owzhpfhYmZ7Vzw162olfF_pewMNc4uKiqRFrKd9sHCzuQ28AAPBj7wX_zdf0HuJzhNgfVM21-9qubLg2RcW795bJwvPTSS6OtKKC0p2nowNg5oYpWZNmbUD_EeD37yX1r1DJC9_rOe_lGW4CH9FyVFvK7u-ZKtOSo9mO6jRinMKGNoa5RxtIWOtiikaZGChfG2LxSLZypfG_X-gTgpzaBpy6TTZiG4pi96iiszf337bz9E0A6RRFFapHEII-i30EqWe_DmJY1XcTgpGa9fJmteNzfwVIlpbBW3XRy1Q1dmFmcFBpXeSIrI6omV5fsGsP2dAaK-0mESg7WyXLxX-TCJHdmxKxumSREAlJv4_C7JtqMjOTmSPMvfLXOWOzJTV2aQ0Sx-n0zbxZGZdb0ugbnvk6CbJ5d0i5pva6p_qbe7fKlu-fVLhbhigt9Isf2VU_OTUOJM_7mU6PULLUwQM1GySbJMesHi0OhBmBguf-VMcC9YDGTpx9eKPiC5NX_bpAznJph02v6CtpRcUVyaW01N0sVhQ-idwDbI2lDab_K5LjW7o8-07BcHd0zp3bDxCOGg5X1vGBO7_J5himxG3msYD6adHv-qUfloK8G_D2yDyoE9c2FHQRDgYdiIkNt9BqTkAUm0pZpK9SiWWNiCt9Pvpk2POwdxOejePeVfxnfKw4hM8HaY-G9EqOXLIRS6hCJ_VhTDhHbYPPCxqyVcNnuz6TSZLY25EOXx3xHwW3gO_qCLP46zoohmw_hlzf_D9GZZFwXDjLYlzbJqSpqz6A-xbFeGraQNemZVBHYF1vUIkFtEDuTQMblfhDmCw5CvKKkx_UJ1LXkTGt4-Z45ZGMuqDQIHYuRYFeVZkkUnIDaVOv1V0fuiQZKeyhqOJTup62wecVm5z39f3JpsViBMj8JJfx6c6-h0-Xi_aThzSI0dUouAFFkCFpJ2AsIXWly_VLI3HwzZR2HwvPf0ee_cMgMMsvbWAGTEImnvmGHuBHaCrlH3_pnKUiByXCcbIhKXiATnCA1716ealWSByvJR3OdmlX5fLMwi63gytcliCOxb5tbBLz_XGuUlHXbPnbhv1T8jOFRDk-NQqcNjDsMoPlHD7Hkc8K6_F3GnlBg5tbXsOfRmPXrjKD1RK82xvuf_w_SOQadhq0sn7FXcPs4T39kylJQ-SsRVIeTWCxbO1gpHW6qaUiFz1y6HskrIZgvHymrlDBvlcHW-i1jH4uhg8IK9Ctr3wzQaHcYxhO9Vv1evzmYwJ6OrfxyuzZU7gW1cMg7Wz27t_XfDC3rwEozRXwSvmXq3vBDfY6ewD4RQ_BcAOSxq36l_1NM_QygfDp7LOlf63Mjft_r77npmlIWTxe-Ew9hdRUQBnMXDBC02FD_tiScD3tbea7R_O_AhBht_HWX13GB0SEh6JEQRSc6k2HMknEi0i99-s3eWFcXv9Iv7Cv1R0wcthzfNLNtHCfeWUK5Zwag0TJ7a7Dg77ndXAQ9IKkqOH719uyg4s3C63VYlw8zOUBNX2h3wcRzE2N9xELfEjYMsTpwwYiHL1kWahzy04yXiifL5wGrhvFechDxe-dkgc6C75WeUhMnMPwXdfu_EMYPLOqFycZsmw5iPpJFDqG8jgtN-jjFVaj_OGWm7MTssnmh5hzRtxp5rLU00Op45P84dW8q7NnEf2cVRkoQZPMviniCTzuyXBtbbjHLGET_GFGOQZjhxSJv1SKNhct6RDdwmlx1vC35BfD0Q5ne-L-T3cLTfKOmLPXgjy2tN1UirpYYThzTokpYnpiT8FmmPEjG9Ozfx0TpaFRwd3b3fCMVFQs7quEBKm4ULVcePT7qNTTv7uzkH0s9P52KXocF0X5pMcNx1HPNZ5A41Yc98IU7oeWpEU1Ef6LEPmuT1Myr3Ln2Krx7oMYxvADgI3S3iKMWz2XkHXdrDTs1Jn06qOr_3P0Yh2irroIl7MQoRP3trsj2O5uci0QDCb4Sc97fojzFS0DIkOSy6G7tRkOBgdpbF6xdNJUflSTY_gg3TgvH1Ic2OQ4dF69CR9uhIUX4-Pj6Kyi5tj5-jnFiLmIY_SVFXdi1wPeAJ-wXUZ0Hqkt5uKyF3cWKcyWVhOjz0KlmYFxE64sGeMzzx2GPszd9Gpa7OoVPphSEM_SB11pWC0J8on-PmOVWzJUdxrWl7aZQs3CriaOqUV2GcwyJ3QteNNHGIkwFVR1Ky0cFRErpKBnGSUpfOZthmXwnTYUZPoxrFl1s9HSBOzRMmGY5z6u6pW5UPeJ73UTg9h3eUoNTq5wBwKhMfozhLC4DxbLVFRsbw4SK8QZ1nhu2GgnNtf0R5DByNlg6MyIWRFTlBYEf-YvZoI0UHzHKLyvLfFGshzapqEFPs7rUYGW0Odx5wEsmeqRzc9gxjN2zESVxklpg3n2GwTTAqyxzhp1XRO7HVjN360GK2ENst4qQ_qc8fEBOVGR2VziGxpZaMr9s00hh432G1wi8vs1nzI0eK4ZWyzVsWncbmwkqbhYja3e6JQ2Vp5oSQnfumybxXpu9Oh5sPTEq0zQlqjtzujnuku_OjP4t82B5J_9QnQWHHFENnO5s7X2q-RAUtXx06f_Txk1Zjx_PTvoth6pw4-r9zEUP6tEJST_2zvpD1UjpJ3Sd3DnHWdugoY-7YdIJ5r6NpcOpBxJmmc6fY6WD74ALCwO46VNQvdSik5L28_CxydZqUn0V-9HTmXGjun2W1J7HfzmPrLD-ETUOWw6ZbjoVBVPgnveyq890pHAYqhlNW-IFsjlDOWnoc_mCvPgnIbpbuKpSd_jaszI8Olp1K2x9ekxjNHNWd2tDPk9SnITBKf_TYjWhn7N57AjAj2TvfPbBdHJlRXyYNfbBamW4rpZHUqw64N49CQ3eUuF_JxSkFjfwPt5kVfhh9967cBbkMSBZk6IJezhIYhmHop9HF5jJAxSwuSBSSJA_DAs38IstiP8thEcG0mF2wS-jD0E9hAP1ZGIZTQnxMaYgISbNZhKgX-nSLWDk1DjoVcn1h3zK7nPlRmkYXJcppqexLjRBy-hXYux6EXnR1IS_tC2p5vVZe6JdMaXUQo5ku6eW8ZEiB3auK4CvTG_DL4-ND88YaVYAVgGmwQQogDmpOn1FZ2zfT1pRTyTBo6iqg0RPja-DF_u7txdi_qGXZf6PyHW_RtRCfL-F_AwAA__9zOMxz">