<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/112559>112559</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang++] Assertion `(isa<CXXMemberCallExpr>(SubExpr) || isa<BlockExpr>(SubExpr)) && "Unexpected SubExpr for CK_UserDefinedConversion."' failed.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:frontend,
            crash-on-invalid,
            clang:frontend:fuzzer,
            regression:18
      </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/avfY3cvM4](https://godbolt.org/z/avfY3cvM4)

This invalid code will crash on Clang Assertion Trunk, it seems that this goes back to clang-18:
```cpp
template <typename Base>
struct Wrap : Base {};

struct S {
    constexpr operator Wrap<S> (this const S& self) {
        return Wrap<S>{self};
    };
    constexpr int operator <<(this Wrap<S> self, int i) {
        return self.base+i;
    }
 int base = 20;
};

void test() {
    constexpr S s;
 static_assert((s << 11) == a);
}
```

Stack dump:
```
clang++: /root/llvm-project/clang/lib/AST/Expr.cpp:1992: clang::Expr* clang::CastExpr::getSubExprAsWritten(): Assertion `(isa<CXXMemberCallExpr>(SubExpr) || isa<BlockExpr>(SubExpr)) && "Unexpected SubExpr for CK_UserDefinedConversion."' 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>:16:33: current parser token ')'
2.      <source>:14:13: parsing function body 'test'
3.      <source>:14:13: in compound statement ('{}')
 #0 0x0000000003bb1d58 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bb1d58)
 #1 0x0000000003bafa1c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bafa1c)
 #2 0x0000000003afcd68 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x0000758f9f042520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x0000758f9f0969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x0000758f9f042476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x0000758f9f0287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000758f9f02871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x0000758f9f039e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x0000000007ad828a clang::CastExpr::getSubExprAsWritten() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7ad828a)
#10 0x0000000006dd4aac clang::TreeTransform<(anonymous namespace)::TransformTypos>::TransformImplicitCastExpr(clang::ImplicitCastExpr*) SemaExprCXX.cpp:0:0
#11 0x0000000006de64be clang::TreeTransform<(anonymous namespace)::TransformTypos>::TransformCXXOperatorCallExpr(clang::CXXOperatorCallExpr*) SemaExprCXX.cpp:0:0
#12 0x0000000006dd2188 clang::TreeTransform<(anonymous namespace)::TransformTypos>::TransformParenExpr(clang::ParenExpr*) SemaExprCXX.cpp:0:0
#13 0x0000000006dd5ba0 clang::TreeTransform<(anonymous namespace)::TransformTypos>::TransformBinaryOperator(clang::BinaryOperator*) SemaExprCXX.cpp:0:0
#14 0x0000000006df0175 (anonymous namespace)::TransformTypos::RecursiveTransformLoop(clang::Expr*, bool&) SemaExprCXX.cpp:0:0
#15 0x0000000006d9380d clang::Sema::CorrectDelayedTyposInExpr(clang::Expr*, clang::VarDecl*, bool, llvm::function_ref<clang::ActionResult<clang::Expr*, true> (clang::Expr*)>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6d9380d)
#16 0x0000000006c60a61 clang::Sema::ActOnConstantExpression(clang::ActionResult<clang::Expr*, true>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6c60a61)
#17 0x00000000066f2d46 clang::Parser::ParseConstantExpressionInExprEvalContext(clang::Parser::TypeCastState) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66f2d46)
#18 0x00000000066ca36b clang::Parser::ParseStaticAssertDeclaration(clang::SourceLocation&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66ca36b)
#19 0x00000000066b8a29 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b8a29)
#20 0x0000000006764f72 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+++0x6764f72)
#21 0x0000000006765ca0 clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6765ca0)
#22 0x0000000006766b75 clang::Parser::ParseCompoundStatementBody(bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6766b75)
#23 0x00000000067682ca clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x67682ca)
#24 0x000000000667be43 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x667be43)
#25 0x00000000066b04fd 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+++0x66b04fd)
#26 0x000000000666fb8e clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x666fb8e)
#27 0x000000000667034e clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x667034e)
#28 0x0000000006677ae3 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6677ae3)
#29 0x00000000066789cd clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66789cd)
#30 0x000000000666aeea clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x666aeea)
#31 0x0000000004526408 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4526408)
#32 0x00000000047e0629 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47e0629)
#33 0x000000000475f1ae clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x475f1ae)
#34 0x00000000048c5dce clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x48c5dce)
#35 0x0000000000cdce6f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcdce6f)
#36 0x0000000000cd4b7a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#37 0x000000000456a119 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
#38 0x0000000003afd214 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3afd214)
#39 0x000000000456a70f 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
#40 0x000000000453000d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x453000d)
#41 0x00000000045310fd 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+++0x45310fd)
#42 0x0000000004538a25 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4538a25)
#43 0x0000000000cd9d3f clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd9d3f)
#44 0x0000000000ba9264 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xba9264)
#45 0x0000758f9f029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#46 0x0000758f9f029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#47 0x0000000000cd462e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd462e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
ASM generation compiler returned: 134
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkW19z4yiQ_zTKC2WXhP4_5MFRkr3szdRMjbO7c08uJLUcdmTQAfLE8-mvADkWsvNvK966q0s5KQua5tc_mqZBhEhJ1wzg0ouvvPj6gvTqgYvLHf2bsCiL4ouS17tLDy88vLh_oBIpkKoiEhCVaA0MBFFQo3KHCGr6X79AzK2w5197_vC34JuOtiDQzWPXcgHCCxfIi68elOqkFy48fOvh2zWvS96qORdrD9_-8vAt2Tb_FVbbz5EXX3s4e7s4zsfdG9yUbUlLa1TxGtBP2raoEkQ-IM5Q0RK2RgspQSjKGboXPfvh4QJRhSTARiL1QBRSWs2ag0QlqX4gxVGlG86CTGOy_SW-_VRdZ0sUbLqWKEBeWKhdB4xsAF0RCV54YyWkEn2l0F-CdEjzoiuRl1556bUXXo3tGCSXptaUIIRQxZlU8NgJxDs9GlwYXV5YLL3wBnk4M8CNGFp6OEES2sbDuatG_whQvWDj5l56ZaRHWLTg9PmAgTJ1wOGFhf4MCMaoLITCiNOXsGjBean5wlf0CIN90EpKw1p4jbB_YO2IwS2ntfFgD2dHvR6MWCJ56Eoqomi1IsY9TLtMDpahIDBawmvdM9FuN-7bdYkxjqXSHlT3m-7YdeyjcS0PX-mPniz4VnCuPHzbttvNrBP8b6j04yB329LSw7eL5b2Hb28eOzHXHhgugjzHur0VCxdeuNC1HnaKCiKVKTZPa1DLvtTPC_mXoEoBs3RpRYdZoqHijErihUXx_ftn2JQgCtK2VtONh7NBjWW68NICWfGrllc_TokZSZxoJ_Uw_oPBYweVji-DCGq4QMV_rv6QIK6hoQzqgrMtCEk5m3sYezhFDaEt1HPL49dPN4vlDZJ9uaEKEVT2aySg40LpCTyJKFQ99OW84puB52O6qZQ9SA_fIsJqRFnV9jUg9QBDNNGRQQlSgXbuTkAneAVSQo0k74Ut1i2JlLyiJnSKniFZCdqp-bPO4c89P_8q-FqQDSJi3W-AKTk4Bu-MIwwxdgb7GDs4x4zsh0zOlI1styVlB9_RPoZm6_onEc0sQrM1mnGtl3Sd1t6rrldziWYbzQWazR6zZEbkZiZ3TJFHL7ymTEGLZg3jsy2IkkvQ9Wi2RLPZuqpmivO2eiCU6YnyEl4tLBnp5ANXaNZUvOViVlOyZlwqWknbh2HaKfbCYqB3H1QDTZhTHC6CxAsXYWimQy8EMIU6IiQIpPgPYMjDqXHB1KrAp1RE-o9RoZtStkZNzyozH_RCqXXY8DIoCV9WQhnSPPCe1SbOgB5XZGZbOiwBFpQNRR4OfeQ_-vufsCyDOs6Q8VUzd-VO2i9fBWXKeNK9dcfsICTIzxWXSgDZmMlmwrCdetkH-ZOHr_zHAZ6DP3Dxk4YE1Sn8RQuE9d0XtqRrRloPZz0zmUqNWq57OQNaA8ZBix20pKnqJEOF9r9vUPEtiJ2F9x-E1a3uNBuYdGQKzhQ8qiEk--b3qYtw6CKNsyZv_AjH2B9MszH9MUtWSTRrKesfZ2vW24pqLvk8McBNEwd25OrMk7ypUKceBJB69UPnPu_qwLR3OoinoKM0QWtpuHgv-ChNHN2JqxtnaRMiUuqI_S7NpqGjOT3SHJTv1hmUjs7M1RnmkCfv02maODrzsdelpM5wRv7Bcv3RE2RAckiucRg44Sip64iQagz1XgDcC8Jkw8XG5oKEcbbb8F4inQvLzkSnfC8-iN7vOi5tuBwX3226llZUPTGAs1Fnx7ULTcMSNkQ_Ft-_H09BbUTgGgFJVMIZjSi-f_8yZMhP6ZJjx0mBt5mCJ-OBgyw7oylfiQB2bMCo-G2wwwnsuCT-GWFfUUbEbs-xi31a9zYDIteAxg_SGL0TpS77BlUvJN0erP3EeecifCK2QCXnrVnC3wAxdiHmYebXY461gsH_uBBQqWtoyQ5qg-7uxCiPcIxK_yTiGqrWAViMVvh9vrQS0HhhMWq5MOXfQPatcmtGPSnRw7CtPSWQmx3Fh4e-gS4n9CUOn1XikyQ4zeeiUl9YoXeXhJnABFLvV1wT3mP9OSy0BjgWpo6FSYPrKEHuNJcgRt-PbbR-c7Ml7ZAEHQWKJw33uw505F7qPPgcFloDHAsz18KKhEn5ooVLcxhgN8HazYkg6mgolybZ_8SroS45izUGrGNN7lpTZgTnL1rzrAX7Ci6ehs2Z5CcsLI56qhdKCVr2Sm-Y3y8x7WNxFhYNSWMWsZvSpEnUpPhVnzAbty9iROiiUSDG9o02YMsNads_odILjDPVl2qjhqke4t7M9JPEjbuvdaO3DdM0Vv_DYfr4YbAsO8MQTIYhrtyU4I3D8L-F93NwpilxOMMTzpIyjV8J2Pbw4Ym7K17vPJzZZfscmDUkB3M4wZzhiryI-XZIIKaYJ-HrGW93PKbiHZzNo7UhjqVujpikJUThmyw1J530OEp_tUdQh2D9Fq-9H15I3LGG2yPvl1t9IgoOUeATlepcodgQ4jAWTxY0P2rqVxe03wTvu2eJWnZQHRv82nr3xkD5LNFvWt2e1XfLxTfC1nDH6NnIN9w65Lv5bZI0ZQavkv9FjJz2jikQ9vDug3ODVwd0UVUgpa6jDQVxFsoMIw5lk4Q59cPodcqGhcph7tnp_uHETf3u3yDO8OIQN8nD05TAy6Hx5tG61rMZ7LnIOgcd2lqHjkkin2Z59XLcu-fdJ9hCaxe-MQ9fOvLfPXxVk4TnKVB-07vwE-nOYff6mdd9C3ebjov93uw8Gxpj5pgH92VHkiQE4Dg3MO88syl0a9D--OFc-YyF5GB28tYoxknkOydwBa_hN2B2u7_f4EPVKxiKznJ2OwBxkDrZYpSCn7jbxVuh10JWn4B6JpAWgwMydEHGTUDApdN2e2dOHio4zejzVp3FlwecjiFO9hdlVVxX4L6WN5AP9myfcoPsJXvPEpQGfI4BTjLmV3UFSYOqKlhtCHW3WQshyO6bPd57IGKfZS5MoCmQW4YLtOW0Po8dFqVjRjIxIypTgvbkF8G9iRSn94x3m649aVPiHnFqHUMeOcqwc1QLugVx8nQ2TN2wkZAgyA0xzx-dmtr9zYzhiLsibVuS6seqYW7At30PPlQEBd9sCKunk_rkGEo1yPFO9040ByN-lKBsPSwjdoCfGqxW1eNjENiHkkharaQRH1h0hHXBSglCldxXT9SRttVzwm7eh3otMjppNk5kOTdNPJy2ZFPWxLxH31OFs_075N95eXo8ssmb3xoH0WgoTr3fHU7we7YkDbQ7h86Xh-4ML7MtYsfz86mLpX6D_j-7iCZ93hGh5v5LvhD5LnGh77tvThzizNiRoxVzz6YTzCcNtcBzW_IXRBdOsjOy7WMTCGP22KGiSaoTBn7zbl5-56V8npTfefmJSuWQ8lJofvKDjlDtAuY2xtt5HJzlX2FTk-WwiSdsZgTHzyG_Hn13EocTGcNzo_AvsnmGdNbQ4_AXThb2vA6H8LbPUPb4TVhZDEHh9WX7w3MSjcyB7uSGfklynERIg_7ovq1qp-_JVR6c1_k77x-ZJo7O6RWeHCIfrVa62UoqItRqZNybe4HI7SWdZnIJBmT1f_yYaeVPvY-rwwUCIbh4umWLmmGHgaphRtgLqegnVQ8IHqmyd9CDMNIwewlotkWKIwmA6CjtHzpbLD_vL9pTbu8Lmrv09oI06CmqdU1uEV_Ul2Gdhzm5gMsgxbmf-3EcXDxc1mFc-2ke4KTETZYkfkiS0sfQhH4U5nV-QS-xj6PAD5IgiuM4mOdJWCZ-7Dd-Q0I_Tr3Ihw2h7VxPnTkX6wtzK_YyCHAc5xctKaGV5v8JMN7Hij0n5opuoSvMJU7OZsO9_EPFtIVOnn790qM2SAhY79-gh4sg0-Xx9YW4NFd1y34tvchvqVTyAFBR1Zp_cRiPXHz9f-g280Uv2st_fl15GJvtJf6fAAAA__-Yf0WT">