<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/112207>112207</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang++] Assertion `!OldParam->hasUnparsedDefaultArg()' failed.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:frontend,
            crash-on-invalid,
            clang:frontend:fuzzer
      </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/szKsjoef8](https://godbolt.org/z/szKsjoef8)

This invalid code will crash on Clang Assertion Trunk, it seems that this goes back to clang-7:
```cpp
class A {
  template <typename T> class B {};
public:
  template <typename T> class D {};
};

class E : public A {
  template <typename T> void foo(A::D<T>, int v = v);
 template <> void foo<A::B<char>>(A::D<A::B<char>>, int) {}
};
```

Stack dump:
```
clang++: /root/llvm-project/clang/lib/Parse/ParseCXXInlineMethods.cpp:477: void clang::Parser::ParseLexedMethodDeclaration(clang::Parser::LateParsedMethodDeclaration&): Assertion `!OldParam->hasUnparsedDefaultArg()' 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 <source>
1.      <source>:10:2: current parser token ';'
2.      <source>:7:1: parsing struct/union/class body 'E'
 #0 0x0000000003ba9d48 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ba9d48)
 #1 0x0000000003ba7a0c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ba7a0c)
 #2 0x0000000003af4c68 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x0000717c83842520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x0000717c838969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x0000717c83842476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x0000717c838287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000717c8382871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x0000717c83839e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x00000000066693f7 clang::Parser::ParseLexedMethodDeclaration(clang::Parser::LateParsedMethodDeclaration&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66693f7)
#10 0x000000000665e92d clang::Parser::ParseLexedMethodDeclarations(clang::Parser::ParsingClass&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x665e92d)
#11 0x00000000066b014f clang::Parser::ParseCXXMemberSpecification(clang::SourceLocation, clang::SourceLocation, clang::ParsedAttributes&, unsigned int, clang::Decl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b014f)
#12 0x00000000066b27a3 clang::Parser::ParseClassSpecifier(clang::tok::TokenKind, clang::SourceLocation, clang::DeclSpec&, clang::Parser::ParsedTemplateInfo&, clang::AccessSpecifier, bool, clang::Parser::DeclSpecContext, clang::ParsedAttributes&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b27a3)
#13 0x0000000006686fa0 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+++0x6686fa0)
#14 0x0000000006644494 clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6644494)
#15 0x0000000006644efe clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6644efe)
#16 0x000000000664c693 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x664c693)
#17 0x000000000664d57d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x664d57d)
#18 0x000000000663fa9a clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x663fa9a)
#19 0x0000000004502248 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4502248)
#20 0x00000000047bbb49 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47bbb49)
#21 0x000000000473a6ee clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x473a6ee)
#22 0x00000000048a16be clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x48a16be)
#23 0x0000000000cdb8ef cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcdb8ef)
#24 0x0000000000cd35fa ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#25 0x0000000004545f19 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
#26 0x0000000003af5114 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3af5114)
#27 0x000000000454650f 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
#28 0x000000000450be4d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x450be4d)
#29 0x000000000450cf3d 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+++0x450cf3d)
#30 0x0000000004514865 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4514865)
#31 0x0000000000cd87bf clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd87bf)
#32 0x0000000000ba7d14 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xba7d14)
#33 0x0000717c83829d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#34 0x0000717c83829e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#35 0x0000000000cd30ae _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd30ae)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkWl9zm7gW_zTKiwYPCDD4IQ-OHe_tbnfa2eTe6ZtHiIOtLUhcSaROP_0dCZwg4rjNTtyX20kTG6Rzfud3_uggRLXmOwFwjdIblK6vaGf2Ul0_8r-pSPIkvSpk-XiNyBKR5f2ea2xAG0Y1YK7xDgQoaqDExSOmuOq-fwc16wejcI3C4fdKNi2vQeHbQ1tLBQrFS4zSm70xrUbxEpENIpudLAtZm5lUO0Q23xHZ6O9_6L8lVDlK14jkPz-cLMbqHW4uHmjNS8xkCfgbr2vMFNV7LAVe1VTs8FJrUIZLge9VJ74issLcYA3QaGz21GBjxewkaFxQ9hUbiZmdGGQWUq9uHvY_rG37K6ymWuMlRtlNfwFjA01bUwMYxSvz2IKgDeB7FN_ifvCNG5ytUTxMabui5uxJyY8lrKcSvM8jXLfYOqKX_7MgHyQvcSUlIvnSYoqXaxSv7C3HmDD4AaN4jR-sE45KPXmelHg1SLlB8YrtqbKCrKyx9FeGOHWILI7mvrT16I-x6XfGeq_smval357IETtEbuyPDVSyUVIaRDZ1_dAErZJ_A7Nfh3GbmheIbD5TpeH4d_XlywdRcwF_gtnLUs9sRMTLJLPB0lvfz3aGuSlq9PkjHKDsp66B1VRRG5iI5K9M-kgNuO-nJs2dJ5ajALeWkuhTXX6mijYBim_3VP9btE7CGira1WZp08plEslwRXkN5ayn5_PH2-XdLdZd0XCDKS66HVbQSmVsTkySlJt9V8yYbAb6XrLIte5AI7LBVJSYC1Z3JWCzhyFBbbIZRRlYh7cKWiUZaA0l1rJT_WU7k2otGXfVSHUCa6Z4a2av-jycoXDxWcmdog2matc1IIwe_C1b59-hbAVwLFuDzwN6pFIHpi8Wm4KL55CwoYODXfmNqipIcLDDgbRyadta6Z1pOzPTOGgsFzgIDvk8oLoJ9KMw9IDiNRcGahxUQgYPoAqpwd7HwR0Ogh1jgZGyZnvKBYrXZ_HawVrQVu-lwUHFZC1VUHK6E1IbznSvwzHtXUbxaqA3vu0Jiyxh3uV4GYUoXhJLGuuUAmGwiyGFjfwKAiOS2VwkWS-BnJBg8yFyVYgqzcUOa6M6FxedcNG76UuVXYasvNsnaRiROMThITz-iwu6KJMcuzBzaaEf9ZArigvjguC-j6T8eZCi37ZSGwW0cbnyXFVs-L9LKCByEx4GeE9rk8UfTfBnNGSn8K9qoKJrP4k7vhO0RiTvhFu3S1xLq-USaC0YDy3x0NIqYfMcr2zo_AVMPoB67OH9i4qytkrzgUlvzEoKAwczVMTQ_X9SEQ8qsihjeZwnJCXhYFpfZQ_5fDtPgpqL7hDsRNffYDMtZ3MH3E3xYCe-zMV8UTHcmr0CWm6_2k7gTQrcfE9BOgWdZHO8046Lt4JPsrkne-7LJnlWxZgWtti-SbKb6EnOXkiOijfLjApPZu7LjBewmL9NppviyVyMo24-ny_iKvu1i-d759ZgxHOXSuIo9K1MYUH-SYugXzfzc19gV7acXsouB9uzK_LtKsIoqc7atfry5U9oClB3LTBecXbCe3duAfkoj_dW-Gdv9n5eGqN40RnQQ8V_qqauYHkzLLnuieYCdDk2PLrIhC6S0fg8XdadA1Wu5I4GG_m1_3BvV-M_uCjfQpU13AoeKDoHorwf2vsPopIvxy-ZbdhGIFe4kLI-I_Woe1grfsaJl3CPZd9zT-y7J59XNDzLzCg1n-yf5OhFef7n_L4ojpbvj1wblwze-A9NW3PGzf3woPgk9QI-cZR7Pkl8nyRJskh-6JNPatMJZlWuofogDKi-rfpxqXjzCC52r7v4hcsuQJljxKMsnVIGFfxsGHvMccFfWVvfm7hpzP0a4qACj7j5hDg2X5wvz7eHPrTONyIXIOsSdFhrPTqyCR1lmp1vWu5l-xEeoO4X1TEPn1r63w4-G4Xi1aQ4_qZk1_4Fldvzmdp-Bw3tP_0py66GD00rlX3UM3CpZcGZ6fGQ-zzEFV3QFzws7-4nXYyF3ht0XA77vxfA7CB5mL22OklDQpJ8jHklS_gNxNKlen_p9gCsMzBccptD7410ADJGSrzWOMmKokgWY6QbZdcbUZ6AeiGQPQYPZOSDjOkcwKezV_tBaEMFg9OMvm7VRWJ5wOkZ4nWgSU6jeeEZMkB-tudBnmrRX9h7kaI04PMM8Hq0kJVFDhVmLNo21MoY7fwslaKPrrC4bWXMpOjbm35z2b9GVm7b9jJ29Cg9M5KJGXFaUXwkfxXdu0oxMuauoXX9H2BGKtuPnbTJ1ZrnKVbG0Ksdx7koKxV_APVyg8bCSv2ykaRVtOj3s5_lVkODsFWOW3d32Et2e34oXjJa1wVlX7eV8At-r3uIoVW0kk1DRTlN6pM-1GYYJ1urnVoORvwYxcVuWEZ6Bz9N2G7Z4RBF_ZeCas622g0_vnAYD7YXtkZRbvTofcR4BK1rmxNSTd5XLJ9LvAuinnM3BZGspk1RUkSyZ6pIftzd-10Wp_0xn-zJpVGUjFxxauetv_NXJ-5oBfWjR-d5111gm7FH7EV-NgmxeRp6Wwb_dyFiSZ-1VJlZeDYW8smSXkBSvkqc8x19sWIe2fSK-WSiHTAqGKszOsZDl16zM7LtnRsIa7YXUNNWh1Xxm3n5XRb6dVJ-l4V9NPZIOVean-KgpdyGwMttp7M8DsHyS9i0ZI3Z9N-5JGmU5PP0NeTr0WevcTjRMbzmhV_I5gXaWUePx180WdjzrBjK27FDOeJ3ZWU5FIUfL9vv3pNYZB50rzcMC5qVUYIt6PfW3Yv2dE_eDJFFuXjjmyE3xZOZTGVCEuLt1k7bakOV2Y6M-2ktkPha0mknF1LAvfz395kV_qR9cpABlJLu6I27jqvhCQOzISP6t_z4Gzd7DAdu-rMyUZxYmJ0GHDxgI7EGwHzU9i8mh3wUmE4JsDlpJ0-OWFyV13G5iBf0Cq6jjOSLyObI1f46TrMYFmE0L8OQLSJKsjKL0ixiNKIlZOUVvyYhSaIwSqIkIiSf0SxLSUSSkJUkS6MYJSE0lNczmyszqXZX7mzBdRQREmZXNS2g1u6gEyHH4nAkARGCyMrecK_CpQiGA0PPN6YzbLf0_bt1E0Hp-kpdu4MNRbfTKAlrro1-BmK4qd0Zq7FL0vU7nMm46lR9_c8PXQzcPFyT_wUAAP__rhidTA">