<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/116783>116783</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Clang-20 crashed at clang::FunctionDecl::getNumParams() 
        </td>
    </tr>

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

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

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

<pre>
    ### Description
I encountered a crash in Clang-20 when compiling the following code snippet:

```cpp
template<typename = int>
struct ct {
 friend void f(ct, int = 0);
};

void test() {
 f(ct<>{});
}
```

###  Command

The compilation command used was:
```sh
clang++  -fno-rtlib-add-rpath  -fno-ident -std=c++23 -Wall -Wextra -flto -O3 -ffast-math -Wall -Wextra -fno-strict-aliasing -fwrapv -g -fsanitize=address  test.cpp 
```

### Error Message
```sh
<source>:3:15: error: friend declaration specifying a default argument must be a definition
    3 |   friend void f(ct, int = 0);
      |               ^
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 -fno-rtlib-add-rpath -fno-ident -std=c++23 -Wall -Wextra -flto -O3 -ffast-math -Wall -Wextra -fno-strict-aliasing -fwrapv -g -fsanitize=address <source>
1.      <source>:7:11: current parser token ')'
2.      <source>:6:13: parsing function body 'test'
3.      <source>:6:13: in compound statement ('{}')
 #0 0x0000000003bf0cf8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bf0cf8)
 #1 0x0000000003bee9fc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bee9fc)
 #2 0x0000000003b3c0e8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x000073de87242520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x000000000751d884 clang::FunctionDecl::getNumParams() const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x751d884)
 #5 0x000000000704ea07 clang::Sema::addInstantiatedParametersToScope(clang::FunctionDecl*, clang::FunctionDecl const*, clang::LocalInstantiationScope&, clang::MultiLevelTemplateArgumentList const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x704ea07)
 #6 0x0000000006fc697a clang::Sema::SubstDefaultArgument(clang::SourceLocation, clang::ParmVarDecl*, clang::MultiLevelTemplateArgumentList const&, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6fc697a)
 #7 0x000000000704ed9b clang::Sema::InstantiateDefaultArgument(clang::SourceLocation, clang::FunctionDecl*, clang::ParmVarDecl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x704ed9b)
 #8 0x0000000006a0b68d clang::Sema::BuildCXXDefaultArgExpr(clang::SourceLocation, clang::FunctionDecl*, clang::ParmVarDecl*, clang::Expr*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a0b68d)
 #9 0x0000000006a2d486 clang::Sema::GatherArgumentsForCall(clang::SourceLocation, clang::FunctionDecl*, clang::FunctionProtoType const*, unsigned int, llvm::ArrayRef<clang::Expr*>, llvm::SmallVectorImpl<clang::Expr*>&, clang::Sema::VariadicCallType, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a2d486)
#10 0x0000000006a2e8c7 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+++0x6a2e8c7)
#11 0x0000000006a30301 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+++0x6a30301)
#12 0x0000000006ddaa4a 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
#13 0x0000000006ddb954 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+++0x6ddb954)
#14 0x0000000006a323da 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+++0x6a323da)
#15 0x0000000006a32d5c 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+++0x6a32d5c)
#16 0x000000000658d99d clang::Parser::ParsePostfixExpressionSuffix(clang::ActionResult<clang::Expr*, true>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x658d99d)
#17 0x0000000006586361 clang::Parser::ParseCastExpression(clang::Parser::CastParseKind, bool, bool&, clang::Parser::TypeCastState, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6586361)
#18 0x00000000065884b7 clang::Parser::ParseCastExpression(clang::Parser::CastParseKind, bool, clang::Parser::TypeCastState, bool, bool*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x65884b7)
#19 0x0000000006588549 clang::Parser::ParseAssignmentExpression(clang::Parser::TypeCastState) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6588549)
#20 0x000000000658cf69 clang::Parser::ParseExpression(clang::Parser::TypeCastState) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x658cf69)
#21 0x000000000660faa9 clang::Parser::ParseExprStatement(clang::Parser::ParsedStmtContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x660faa9)
#22 0x0000000006605c5e clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::ParsedAttributes&, clang::ParsedAttributes&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6605c5e)
#23 0x0000000006606bb0 clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6606bb0)
#24 0x0000000006607a95 clang::Parser::ParseCompoundStatementBody(bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6607a95)
#25 0x000000000660929a clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x660929a)
#26 0x000000000651d103 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x651d103)
#27 0x00000000065518bd 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+++0x65518bd)
#28 0x0000000006510e4e clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6510e4e)
#29 0x000000000651160e clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x651160e)
#30 0x0000000006518da3 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6518da3)
#31 0x0000000006519c8d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6519c8d)
#32 0x000000000650c1aa clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x650c1aa)
#33 0x00000000045736a8 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x45736a8)
#34 0x000000000482df89 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x482df89)
#35 0x00000000047ade9e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47ade9e)
#36 0x0000000004918d3e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4918d3e)
#37 0x0000000000ca83a7 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xca83a7)
#38 0x0000000000c9ff6a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#39 0x00000000045b68a9 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
#40 0x0000000003b3c594 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3b3c594)
#41 0x00000000045b6e9f 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
#42 0x000000000457d18d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x457d18d)
#43 0x000000000457e27d 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+++0x457e27d)
#44 0x0000000004585635 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4585635)
#45 0x0000000000ca5213 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xca5213)
#46 0x0000000000b7be24 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xb7be24)
#47 0x000073de87229d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#48 0x000073de87229e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#49 0x0000000000c9fa1e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc9fa1e)
clang++: error: clang frontend command failed with exit code 139 (use -v to see invocation)
Compiler returned: 139
```

The issue can also be reproduced on Compiler Explorer:https://godbolt.org/z/h8oYGx78a
Please let me know if you need any more details.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkm91z2ziSwP8a-gVFF79FPvhBkeO5zGU2rsg3u_fkAoGmhAsF8ADQlvevvwJAfYCWFGfWnMrNujIemsRH96-7gSYIYKXYigPcBPmHIL-9wr1eC3nD8AZzwV82oldEXdWCvtwESer-oVtQRLJOM8GD6DaI5p8QcCJ6rkECRRgRidUaMY4WLearMInQ8xo4ImLTsZbxFdJrQI1oW_Fs_iKCAlKcdR3oIJ27NoffReT-ka5zdzRsuhZrCNKFfumA4w2gIL1FjOsg_ejKKC17ohHRKJh9cLdQIxlwip4Eo6gJkpLoIFmYWrZ2FCRVkA5lg9nt4dr-trU0KB0kZZBUx826ptKF6Xz2wVQdteTr4Sm3J4oWYrPBnB4_fVjDQAwb0ubaFEG9AoqesTqQ2rWt1u4GMdSD5EOQfEAobLgIpW5ZHWJKQ9lhvR7uMgpco1BpGqS3xFVIUhT-HbctCv8OWy0xCptWCxR-SVHYNFjpcGMaGJfhIlRaMqJD3DKsjFXD5lni7gmF5lJhzjT7JwTpLaZUglLI8rwmXYfehOijlEKi30ApvIIzigfpQoleEjDGSOdpkM7jPEjnCExlczF4AQXSYum4qg4Ia16MyBhRaHDfaoTlqt8YOpteaVSDe8SMEjunRwihFAWzBUI_4lzI_rhqxz9BPjjv_eeP8-VHpPp6wzTCqO5XSEInpEZaoLXWnTV9chckdyum1319TcQmSO7a9mn3v7CT4n_ASHHHlOpBBckdMs7DOGl7CjYAXZTWmHzTEhMwEncSOikIKONjA8pkYWtipQRhWANFsufIjQDXTuSlxuQbov2m2ztldB1E1b0UK4k3e5pGcBQkd6IzkjnnBhnCtmuFBGnu2QEDKwXSkFahlj3_FiR3NeO7x4Nnhyv6jGUTZtbDhGkXd51pvdddr68VCjeGBQrDbVmEWG1C9cI13gbpLeMaWue2TyBrocA8R-ESheGKkFAL0ZI1ZjxIby_Kaworjju1FhqFDRGtkCFleMWF0owo14cl_fr2OCp_gqD0IsgaMjaGHAXWzARWbIxJeimNvB2WCiTS4htwFCQz4_HJzLWQnGihMC2Y-LQ1jWRNz4mNRzPZmCbccDu0kV5sg7m5RfScIqWxBhu6dqye7QZlK5KLwCBJIxRto91PWjcRaUpkAyidB-lcvSh3cS8Z19a9H1yMlIdCEj8_CqUl4E2QFEPA29nBdPwuTh4kH6LtIJ4nf-zLD1A15JT8ixYw77svfMlWHLdBUvbczvgUtcL0MoG0VhhP2sSXNiURlGhhguIrEPEE8sWJ9x-Y09Z0Wg4kvTILwTVs7ZQRpPPI_rfvIh26mKUUylmSJXkSDaq1rA6Su21ZPBZZ2DLeb8MV790Dcq3EdWEFt1U8sbNjsWd5TMsyQ05fC_ducNlbIK27swL9t35zjyXeqCFVIIIr_d6QB2E8aXNP2igDHM2OpV3CBrsrTOknrjTm2o7nVlzQINWDWBLRGS8_p2UyN35-5qnT9XWZz4Lg9tAjE3zophgV_K1vNfsMT9A-DFnefJg5PjOld80XE3jtwMsDWhwDLRpSVDN8Guiyr5W-danDTmIf4tKOWwaETSB8te-x3PyO5WnAb2ayQLUQ7QRsBtU9NrOxs9GqPs3myNP-OKHLPjjmN4l30Kr2CJSed-CoLkp6msCHnrV08Y9_HNT_uO3kZNp7D11PUzAZVPaYVD6ThGZlcZrJL1ivQe48Qd0JucBt-25Mdk_vpdDi4aUDb2jaT4F2llkczZtzKfHLV2iCdHECYvrRL73c4Lb9HYgW8tOma89XGo9zBw6_Y8kwZcRob-Q8hPF04ezssjecySaikeGgJGfmjoXgTyD1ZcuZO3vPO-2P72bMHzPeRfeaDrjh6QGPfeBplEbxhdHjKyjRPgE9gC2_C_VveAP0NNHXqr8jxdOC7Zz6lJe4fm8_mxv_yTidxAYWsWcDLystKMU4w-iOcabWX55AtgLTc8SteV6Htctq3ubz_8XlYNTPQnzru9OlLlnqt17juoWJDHZ0d0djgTllFGtYwoks71UpW-RcKcZXX0H1rT4OPIN1V-B1mm9slo5sVld5diFuvmvHv5LFpp43HG0vhLLRMJak9EyK7JKgf90If128jp6HNx_jpTk5jXdO9Bf-_xjvJDhpTjyc_gtdXtKqoqNMWoE8ur4XSjdsa6QEpcx7a980bOvzndvkZBjMTjJJFkjL3q5aTaCo08NTdDZStEiL-KKiC6z0QUtfv-PCppz9203T46AYT4jHVU3iZqovtZ0axlUn8QGnuYemHKEps3o2LZqfiodR1-NRjXnkWXWRx9x-MTS5_1uojLScRKU8q45VSqKRSqQpLqv0kyhi5PQU8V8SiqjB-PuKLHfr3-d1sdd0qTd6WFKdQh8nrqdPMtInJzlc1Gevyxe7vDF8sZs3GuRca8nqXoPy1uSPXsn9sdhoO4zFadKffCv_DqKLs9qJRRkF9FjIk72NS0xhBkPZM0M6MkNR19EfMMPPwn0KZgaJxywbMZvhKr88bQzfo_bsPgj6EiTlVNmjE8mTOR_JXCUVvijzbqFlLPNRnbNLkCOP2a_vT6GpUcTTdJTYxTSO0jdpenv4pv9qtGR8tfN2Id_itbv1-U-8Ed66_Jlan7GGwyjwmQ1LWhNMLRaIR2yUIeZxWV9OhQ2KX6Tou7Oglh2Q1wofEJ4O6DcOlGdBn1iFecvQPLR3J-RXzFfwibPJ4Fu2HvxRDhpHkF2eBw3EL_LIaT9xDdJ9z_3XJ51XJS4adE4IKLW0m2aYITKFvxoiHrJRmhrHRfR9ZMNE5ZE7G-7vDm7sd38KOMPlGFw6SobjkuLLQ-PHrXMtf6b_E2BNgcNo6-GIRzgqUl4e9x5EZz--uonvmMOXDv9vD_d6lPDsB0q7RHLx489vgvYtfNp0Qu7eKyaZMZ2aHgc_Fc8jEuPXucF8-XB22Xvq1TAnkiezl7dm-SwtcOl9TxAUfgHu1mN2KzBAeg3DrWHv5vtKOgjiSepli1mZ0Kb0XtzupJkLOT0h6kRCOhk8Ib30MJthChX4OF237gM-gdNEz2s1iS8PcnqKeNlfVsUlTcFfZLQiH_R52ucG5SV9JxmUBvk8BbxkLCK4TPEMERI_bjDzX7OO117XWB4-hA7Lrt69ZGE3pE6jh5PSU6P01aiapsBoB38RP9iR4vQ74-7z-SudCn8J2rQx5JHebiAq2RPIk5-M_E0JWV4XJa7cTt1Du7vNh4_SsrVPXSS6rYZBOie4bWtMvj023B_wXd-DDy3i3U7uUVCftKHd5GnuCbuZHhsGR3y0tF_J7DTiDLyv8PhItlu7BTNI5zVWjDwqW3yg6BU2Nx61xEyr3eNRc7htTUy4l_fhuSkyHy1IOua2SpDMWrypKbZbK3eoknK3rfBXUZ-0RxaNNwPmVXZkilNb_tyTrz1f4gbaFw_nZdNNsb_RSnzs-Vk8djGoGvTv7CIG-nWHpb6OLvpCMprSaeynYx64w1mI8bhuaXqD-aiiPThx5pX8QtH5aGPdJHs5B7U9hxqnOpDMfpjLr6JW56H8KupX-wcvDc17P-gwMy4wbJ16K8fBWf4UmgaWR9NPx_IyL9L8nOS3R9de4nAiYzhnhT-R5gTprMXj8ctH-UmexMM75C5D2clvh5X5q51Z56btd89JjGSe6F5uGNWzGpIMGaHfu2_XtNf3zN-SnlS0-sEt6baK12Y5bhOyCD0-mmqPSmOpH4-Ue3MvkPm9VONMDseAXPvvbjPb-L7348fH57bsfdQMbxj7s3ANZi1Q9Mz0GsGWaXeUME6ta_UKUPiEtEAKALGjtH_obJfxIwm6lxxMTJrKF86jPawB2RNViGCOcKsEqgHZU1O0J0CR4Gjf7McdlXQ-OrYlaC1afS3kKkju_hkkd-tS_Pcv21mJhzNgLWAFqAWNNoC-cfGMWINeRI84AEWYv6CNkIAoaMxadX1Fb1JapRW-gpt4liZRnFZldrW-ydO4IJAnaZIUEBdJhqGp05TGM6giKOordpNESRbHcRVHeZVl10kWQV3WVQFQVlAmQRbBBrP22oSzkfjK6n8Tx8WsTK9aXEOr7PHRJBmslwT57ZW8sQfR6n6lgixqmdLq0IRmuoWb_elQez7K6KV_-HjFVS_bmz9-KG7Q4ukm-b8AAAD__617LZg">