<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/139053>139053</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Clang Crashes When Instantiating a Static Templated Method With void Parameter Pack since first clang (3.0.0)
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          mariete1223
      </td>
    </tr>
</table>

<pre>
    Clang crashes when instantiating a call to a templated static method with a void type in the parameter pack. The issue appears in the template specialization my_if<0, true>::run<void>(), even though the method does not use the type itself.

## Assertion

```
lang++: /root/llvm-project/llvm/tools/clang/lib/Sema/SemaExpr.cpp:5562: clang::ExprResult clang::Sema::BuildCXXDefaultArgExpr(clang::SourceLocation, clang::FunctionDecl*, clang::ParmVarDecl*, clang::Expr*): Assertion `Param->hasDefaultArg() && "can't build nonexistent default arg"' failed.
```

## Stack dump

```
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 -x c++ <source>
1.      <source>:20:31: current parser token ')'
2.      <source>:19:1: parsing function body 'main'
3.      <source>:19:1: in compound statement ('{}')
 #0 0x0000000003f7c0a8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f7c0a8)
 #1 0x0000000003f79d34 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f79d34)
 #2 0x0000000003ebebf8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x0000793fea242520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x0000793fea2969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x0000793fea242476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x0000793fea2287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000793fea22871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x0000793fea239e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x0000000006b1cab5 clang::Sema::BuildCXXDefaultArgExpr(clang::SourceLocation, clang::FunctionDecl*, clang::ParmVarDecl*, clang::Expr*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6b1cab5)
#10 0x0000000006b3f116 clang::Sema::GatherArgumentsForCall(clang::SourceLocation, clang::FunctionDecl*, clang::FunctionProtoType const*, unsigned int, llvm::ArrayRef<clang::Expr*>, llvm::SmallVectorImpl<clang::Expr*>&, clang::VariadicCallType, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6b3f116)
#11 0x0000000006b40636 clang::Sema::ConvertArgumentsForCall(clang::CallExpr*, clang::Expr*, clang::FunctionDecl*, clang::FunctionProtoType const*, llvm::ArrayRef<clang::Expr*>, clang::SourceLocation, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6b40636)
#12 0x0000000006b41fe1 clang::Sema::BuildResolvedCallExpr(clang::Expr*, clang::NamedDecl*, clang::SourceLocation, llvm::ArrayRef<clang::Expr*>, clang::SourceLocation, clang::Expr*, bool, clang::CallExpr::ADLCallKind) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6b41fe1)
#13 0x0000000006f491ba FinishOverloadedCallExpr(clang::Sema&, clang::Scope*, clang::Expr*, clang::UnresolvedLookupExpr*, clang::SourceLocation, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation, clang::Expr*, clang::OverloadCandidateSet*, clang::OverloadCandidate**, clang::OverloadingResult, bool) SemaOverload.cpp:0:0
#14 0x0000000006f49e90 clang::Sema::BuildOverloadedCallExpr(clang::Scope*, clang::Expr*, clang::UnresolvedLookupExpr*, clang::SourceLocation, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation, clang::Expr*, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6f49e90)
#15 0x0000000006b43c86 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+++0x6b43c86)
#16 0x0000000006b44cfe 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+++0x6b44cfe)
#17 0x0000000006675ced clang::Parser::ParsePostfixExpressionSuffix(clang::ActionResult<clang::Expr*, true>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6675ced)
#18 0x000000000666e6fa clang::Parser::ParseCastExpression(clang::CastParseKind, bool, bool&, clang::TypeCastState, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x666e6fa)
#19 0x0000000006670897 clang::Parser::ParseCastExpression(clang::CastParseKind, bool, clang::TypeCastState, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6670897)
#20 0x0000000006670929 clang::Parser::ParseAssignmentExpression(clang::TypeCastState) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6670929)
#21 0x0000000006675309 clang::Parser::ParseExpression(clang::TypeCastState) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6675309)
#22 0x00000000066f95e9 clang::Parser::ParseExprStatement(clang::Parser::ParsedStmtContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66f95e9)
#23 0x00000000066f10a2 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+++0x66f10a2)
#24 0x00000000066f1fcd clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 24u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66f1fcd)
#25 0x00000000066f9ce3 clang::Parser::ParseCompoundStatementBody(bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66f9ce3)
#26 0x00000000066fa4aa clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66fa4aa)
#27 0x0000000006601a53 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6601a53)
#28 0x00000000066380fd 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+++0x66380fd)
#29 0x00000000065f558e clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65f558e)
#30 0x00000000065f5d49 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65f5d49)
#31 0x00000000065fd66a clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65fd66a)
#32 0x00000000065fe60d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65fe60d)
#33 0x00000000065f09ea clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65f09ea)
#34 0x000000000491ebe8 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x491ebe8)
#35 0x0000000004c11f15 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4c11f15)
#36 0x0000000004b9131e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4b9131e)
#37 0x0000000004d05d39 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4d05d39)
#38 0x0000000000da788f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda788f)
#39 0x0000000000d9da5a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#40 0x00000000049854a9 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 0x0000000003ebf094 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ebf094)
#42 0x0000000004985abf 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 0x0000000004947f0d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4947f0d)
#44 0x0000000004948f9e 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+++0x4948f9e)
#45 0x0000000004950df5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4950df5)
#46 0x0000000000da37f8 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda37f8)
#47 0x0000000000c28b74 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc28b74)
#48 0x0000793fea229d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#49 0x0000793fea229e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#50 0x0000000000d9d505 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xd9d505)
```

## Program

```
#include <iostream>
template<int M, bool E = false>
struct my_if
{
    template<typename... _Types>
    static void run(_Types &&... __args) noexcept
    {
    }
};
template<typename... _Types>
struct my_if<0, true>
{
    template<typename... _Args>
    static void run(_Args &&...) noexcept
    {
    }
};
int main()
{
    my_if<0, true>::run<void>();
}
```

## To quickly reproduce

happens from clang 3.0.0 until current

https://gcc.godbolt.org/z/bqM3bd8vx
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzkW19z27ay_zT0C0YaEvwj8sEPtBz3pje58cS-bd80ILiUcEwBLAA6cj_9GYCkIdKSYk-ttKen405sYrH47W8XiyUIEKXYmgNcevGVF19fkFZvhLzcEslAQ4BxeFGI8ulyWRO-RlQStQGFvm2AI8aVJlwzohlfI4IoqWukBSJIw7apiYYSKU00o2gLeiNK9I3pDSLoUbAS6acGEONIbwA1RJItaJCoIfRhju43gJhSLSDSNECkGgQHxUg1QBmp2R9EM8HR9mnFKi9c-h5eIi1b8MIPXph7YS5b7oVLM6J5hFMPZ0YGHsFoFO16YxX3AEsBCnGhUaugG9Ci1Arqau75ufnBoYdDlCsF0ozdP038_sfPDVMevjI_YY48fCOF0B6-qevH7ayR4l9Ahz89fKOFqJWHb2jX7aZmhYdv7mBL-n8-7Bo5p03jhXkcJ9jo7GStfab1K6i21vtPbXf721XL6nL522_XUJG21rlcmx4eTvelRSspfBLUkmno2Wu8aTk1j6-B1h7OJ623RG5_IfJwYzdSbigPc8cY8hL_1nh85oUfNkQ5aJ1_kIcTDyfIw5gS7uGFRoWxAnHBYceUBq5R2XVCxPTCHl6girAayvnEGc5jd5rQB1S22-aly_baQtPmzz0_u5ViLcnWDNFugWvVu1M0xn1UbBtWg5zBrqmFBDn4cEYGQ9VMy5Y_ePimYNy52EQGmq3Lb0RWswjN1mgmjF7SNEZ7q5tWzxWabU2EoNlslyYzorYz9cQ12XnhNeMaajSruJg9giyEAtOOZndoNltTOjMhRTeEcS-8PonXCCtOGrURGs0qKmohZyUjay6UZlR1Y9hJP368Q7S3wwuXyoaPmV5-HhjiRs_CHPtemIeBDdxWSuO9hkgFEmnxABx5eGFn5cLzc3ygf2DCx3Y33UyuqfqYRCY1mf5bY6xVEJ5UwDgyPIiWd6kJjF-RDbuFt7jyFtc9GN94OvSRv_OH_8JqQX2SIjtvbXyrJ9XPAsm4tjF0LwkFD6dOSJJvK6G0BLK1cb1EjOsuytN3CiYPX_m7Hp4DH0zAZ2UYHQK_rIHwtvnC79iak9rDacvtmlCiWpghzgHVgHFQ8QgqFFBUKVqasPsKVDyCfOqw_Q_hZW1GTHsORzJLwTXsdJ8rfft_pz_s9S-ysAKCIxxjvzeqS7e7NFkl0axmvN3N1rztGuhciXliIdsuDnA0VpglWUVRozcSSLl6YHX9Nu22v9MeT-FGiwStlaXgrbCjReIUJ2PFOF1UISKFkPptam1Hp3bxQm1QvFlhUDiF6VhhmEGWvE2h7eIUZvsBlhQBJUX8d14v33vG9SZ3hJjc4I8JCasgSA4T8hPRG5D5sAbeCLkkdf1uhAytt1JocW-qLSq40r3gcyay8325l75yKcnTVzBF3wEGTam3L323JXX9C1At5MdtUx_vlEzg_UIkIyWjxmaDzjQXQtTu3zP4ynrD-SoY-yryk_CIr5aCP4LUp51lnjxH2uH4ezf_vc1fJyPqbGxbPh3beMJ2UEFwIlV8BSXqRygdq-l3Gf0_soXyMJ0v7X5HCg8DG8L5UIh0415_Mg_-l_HyPA4wFDsHhCMHVFEWFATdMM7U5ssjyFqQ8hjd3VvTdA7fUWEm7uui_f-57D36SYiHtjksdcpNn1tNihrO5K29pwMbS8JLVhINd6BfIWVFjkkxvu7eJvennKF1EJhUV8Zh0dRhkPknZsx3nfhPcte514qObTd54kn2Cml6ZK3oCp0_74F_Lrcde47bZMJtRCs4zG1O9Rf-H8ztObg0bDkuFyMuk0VMoZzUyQrk3u-3QumK7QxEUIoJftdWFduNyc1tKdInsIOE7G0PnsHKzg5nZTq2MoGkIietXBKlnYnTuk1pK9QtxNP4n656phYzXe60zflT8bN4ubPQ2Z9NvOyn2eL97f-rjbZmPRuN_anRGc5OGp3bLXhTsB8zfWLWWWzIcOZsCKbTM_RP2_AXIjfYHPJx-Z5UWQzfR343bAWOwb-QLe_0VvfbTGcxxsJ1xoQTYwKf4JPGPBvyxW4xEGnTfF5pkLnWkhWtBjXantx7Mx5nTGNqnzFx1B58Of4OPycXngMbIwrKfZAHR5tKnMMHhmXng2jqg4qeXqkO--DvQvpZCKuoW_RwPJ2BFMLTSb_fkX8m7kqUTx5Oz1XXdZAc4GQCmETk9Co97HlMAe_1Obr7N4mVrho8UyAbQ5yZk5LLD0h82i9u46dinOkXuf22-xozBLmQrwnW-_4L7kdeiWGr6FSvT0SDm_mfWL-1dAa6LCGOrkntFqZ-dXreGx5-kqJtjrJ01wB9aa3j7_AkfmVmPMrygQ2R1-TiXt-NkF8JX8NHzs7GvOXWMT-uGuMqjlP4LvNf5F64fuQaZPct688vMS8kTnozpxSUMm2sYoaO9-erY-SZr_FXStNaRqdLnr1laUTb0Vn-7qxNI-7HsFZGrrYafx5N4qpMktNZ_8OuC6rxov4DmDoHF8ZaxwWecAGJfzrX3YvmEzxC3S1z-yR8acjvLdzqSWHznBztVsWBssZtnnwWZVvDx20j5PDacJb1sTPTkRBOSPAzeBkQ-d390S3nc-9HdZAc4FFlGmUBFJCOdvFFCT8B7zZFhm0QoK2G_tFw2uZdYfZAHMxRPRjRIKiC0bfXG2mWPV4ewHkmhB0Gh3BUAEZFFoQBjInsxvxoD7xROMzlcZPOEr89TmfFqL6LSj8uw2y8u2fxOmMenwuA9JSxZ0lBPT6HflRu-SVZpGmFKA1W3dGe9PBnsA2R7ntjv9k5eoaX9rTheYzoUDobsrENWUliggbal8G9zQuHXwOHr9IvDErGu75GR18m7lXPGSolewT58uNM5I-TRBpHJOsOYDqlw3GqlbSs2tb-qORwjJKSui4IfVhVfJzYu4H70FkGS7HdEl5OZ_FB7yndy4nGjE4MAXvkaGk_RtnlonPtc4fViu52QdD9URDF6EpZ8Z7CkbB5sNKSMK2G5ok6UtdmKnQv4327EcknO4cd4baLhxc12RYlsefFBqpwOpyY-lkUB5wRTM45VX62fyTr0GmmruVry-9IBfXTiMvTfjvDua0O8XPAR3gaXKSo0H9zcBjG5w2Reu4fj4JwzFq0qMbV1og16zXyYmUcqByl7klHI3DsFfuEaD4qZ_YMe98qwZrtQmlSzERplcFbSflZFOo4Iz-L4hNTesTIqVz8HAENYcb5_RGk15LYh8kPodKQ5agcF1xZ7JdVfAz29d7vowLhQGVwzAU_kMozVKuWHkdeMqlDwkXVF9VDJTKAt6kkf3HQ6dgK_e61h0HmcI-qP5_itFhEyCB-74E71W7gyVlNnJXZG8_W2i5OYTZVCJGPVivTZ6U0kXq1Z9arh4DIDRH700It9mPUKX93P1nl_dAH7yX01wxeXkrwcMg4rdsSkJkzwyFye85-uAjTTSb0ecgy6APywmtUkVr1J_KVli3V_Q0ZP_cWV56fI4TQngr91AAnW5jP52h1_9SA6voasf4Gjy0uZGsmQCfR39KwXVZErpUJci5gR6HRfV83mLe4toNfe-HVGP6xsUe4Jzd7XmNGbiCdssIIOCPegt4w3ieD3rHPkm-7iGS19coPxsa9QL-3jD7UT0hCI0XZUugENqRpgCtUSbHt8hMK5_7cRy3XrB4uWvSyWjf2sD--6S59zNeiLESt50KuPXzzh4ne3z-HRZk-7i7Ky7DMwoxcwGWwiJIkS3CQXmwuy9QnabFIQ0irEONFQTGJgAZRVCwWuKIX7BL7OPZjP_Uz80Y3j2PIMA2KsAiqOC7Ai3zYElbPTbY0Y1_YS16XQZj5cXhRkwJqNVxEk5f2vlTRrpUX-TVTWrl-muka-jtpy_5O2q8b4Ojj5E7aXef3--cLaZ-7i16_Mr3pouH2-e7ZLaEPSDFOAVVMqv5ClUkIllkPZxetrC8nbDK9aYs5FVt3pWty0csaqTx809v5eIn_HQAA__9rkA7q">