<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/62102>62102</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] Invalid cast assertion in clang::Sema::PrintInstantiationStack()
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            c++,
            clang:frontend,
            crash-on-invalid
      </td>
    </tr>

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

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

<pre>
    For:

```
template <typename> struct S {};
template <typename T, typename U> constexpr bool operator==(S<T>, S<U> x) {
  return 0 == x;
}

struct E {
 friend bool operator==(const E&, const E&);
  S<int> s;
};
bool operator==(const E&, const E&) = default;
```

Clang crashes while printing out diagnostics:

```
$ clang -cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -std=c++20 /tmp/a.cc
/tmp/a.cc:3:12: error: invalid operands to binary expression ('int' and 'S<int>')
  return 0 == x;
         ~ ^ ~
/tmp/a.cc:10:35: note: in instantiation of function template specialization 'operator==<int, int>' requested here
bool operator==(const E&, const E&) = default;
                                  ^
clang: /work/llvm-project/llvm/include/llvm/Support/Casting.h:579: decltype(auto) llvm::cast(From *) [To = clang::CXXRecordDecl, From = clang::DeclContext]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' 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: build/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -std=c++20 /tmp/a.cc
1.      <eof> parser at end of file
2.      /tmp/a.cc:2:50: instantiating function definition 'operator==<int, int>'
 #0 0x0000559070d83ad8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (build/bin/clang+0x34dcad8)
 #1 0x0000559070d8177e llvm::sys::RunSignalHandlers() (build/bin/clang+0x34da77e)
 #2 0x0000559070d8415d SignalHandler(int) Signals.cpp:0:0
 #3 0x00007fc45685af90 (/lib/x86_64-linux-gnu/libc.so.6+0x3bf90)
 #4 0x00007fc4568a9ccc __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #5 0x00007fc45685aef2 raise ./signal/../sysdeps/posix/raise.c:27:6
 #6 0x00007fc456845472 abort ./stdlib/abort.c:81:7
 #7 0x00007fc456845395 _nl_load_domain ./intl/loadmsgcat.c:1177:9
 #8 0x00007fc456853df2 (/lib/x86_64-linux-gnu/libc.so.6+0x34df2)
 #9 0x000055907365af60 clang::Sema::PrintInstantiationStack() (build/bin/clang+0x5db3f60)
#10 0x0000559072df38cc clang::Sema::EmitCurrentDiagnostic(unsigned int) (build/bin/clang+0x554c8cc)
#11 0x0000559072df47d7 clang::Sema::ImmediateDiagBuilder::~ImmediateDiagBuilder() (build/bin/clang+0x554d7d7)
#12 0x0000559072df4948 clang::Sema::SemaDiagnosticBuilder::~SemaDiagnosticBuilder() (build/bin/clang+0x554d948)
#13 0x00005590730f0e58 clang::Sema::InvalidOperands(clang::SourceLocation, clang::ActionResult<clang::Expr*, true>&, clang::ActionResult<clang::Expr*, true>&) (build/bin/clang+0x5849e58)
#14 0x00005590730f94eb clang::Sema::CheckCompareOperands(clang::ActionResult<clang::Expr*, true>&, clang::ActionResult<clang::Expr*, true>&, clang::SourceLocation, clang::BinaryOperatorKind) (build/bin/clang+0x58524eb)
#15 0x00005590730de72e clang::Sema::CreateBuiltinBinOp(clang::SourceLocation, clang::BinaryOperatorKind, clang::Expr*, clang::Expr*) (build/bin/clang+0x583772e)
#16 0x000055907347f926 clang::Sema::CreateOverloadedBinOp(clang::SourceLocation, clang::BinaryOperatorKind, clang::UnresolvedSetImpl const&, clang::Expr*, clang::Expr*, bool, bool, clang::FunctionDecl*) (build/bin/clang+0x5bd8926)
#17 0x0000559073677368 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::RebuildCXXOperatorCallExpr(clang::OverloadedOperatorKind, clang::SourceLocation, clang::Expr*, clang::Expr*, clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#18 0x000055907366cfdd clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCXXOperatorCallExpr(clang::CXXOperatorCallExpr*) SemaTemplateInstantiate.cpp:0:0
#19 0x0000559073693d45 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformReturnStmt(clang::ReturnStmt*) SemaTemplateInstantiate.cpp:0:0
#20 0x0000559073681d26 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#21 0x0000559073662ab3 clang::Sema::SubstStmt(clang::Stmt*, clang::MultiLevelTemplateArgumentList const&) (build/bin/clang+0x5dbbab3)
#22 0x00005590736bbae7 clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) (build/bin/clang+0x5e14ae7)
#23 0x0000559073200aaa void llvm::function_ref<void ()>::callback_fn<clang::Sema::MarkFunctionReferenced(clang::SourceLocation, clang::FunctionDecl*, bool)::$_0>(long) SemaExpr.cpp:0:0
#24 0x0000559072ded3af clang::Sema::runWithSufficientStackSpace(clang::SourceLocation, llvm::function_ref<void ()>) (build/bin/clang+0x55463af)
#25 0x000055907310a99a clang::Sema::MarkFunctionReferenced(clang::SourceLocation, clang::FunctionDecl*, bool) (build/bin/clang+0x586399a)
#26 0x000055907310fd06 MarkExprReferenced(clang::Sema&, clang::SourceLocation, clang::Decl*, clang::Expr*, bool, llvm::DenseMap<clang::VarDecl const*, int, llvm::DenseMapInfo<clang::VarDecl const*, void>, llvm::detail::DenseMapPair<clang::VarDecl const*, int>>&) SemaExpr.cpp:0:0
#27 0x00005590730cf98b clang::Sema::MarkDeclRefReferenced(clang::DeclRefExpr*, clang::Expr const*) (build/bin/clang+0x582898b)
#28 0x000055907347e39e CreateFunctionRefExpr(clang::Sema&, clang::FunctionDecl*, clang::NamedDecl*, clang::Expr const*, bool, clang::SourceLocation, clang::DeclarationNameLoc const&) SemaOverload.cpp:0:0
#29 0x000055907347febe clang::Sema::CreateOverloadedBinOp(clang::SourceLocation, clang::BinaryOperatorKind, clang::UnresolvedSetImpl const&, clang::Expr*, clang::Expr*, bool, bool, clang::FunctionDecl*) (build/bin/clang+0x5bd8ebe)
#30 0x0000559073051bf6 (anonymous namespace)::DefaultedComparisonSynthesizer::visitExpandedSubobject(clang::QualType, std::pair<clang::ActionResult<clang::Expr*, true>, clang::ActionResult<clang::Expr*, true>>) SemaDeclCXX.cpp:0:0
#31 0x0000559073051a19 (anonymous namespace)::DefaultedComparisonVisitor<(anonymous namespace)::DefaultedComparisonSynthesizer, (anonymous namespace)::StmtListResult, clang::ActionResult<clang::Stmt*, true>, std::pair<clang::ActionResult<clang::Expr*, true>, clang::ActionResult<clang::Expr*, true>>>::visitSubobjects((anonymous namespace)::StmtListResult&, clang::CXXRecordDecl*, clang::Qualifiers) SemaDeclCXX.cpp:0:0
#32 0x00005590730220e0 (anonymous namespace)::DefaultedComparisonSynthesizer::build() SemaDeclCXX.cpp:0:0
#33 0x0000559073021d12 clang::Sema::DefineDefaultedComparison(clang::SourceLocation, clang::FunctionDecl*, clang::Sema::DefaultedComparisonKind) (build/bin/clang+0x577ad12)
#34 0x0000559073040de6 clang::Sema::SetDeclDefaulted(clang::Decl*, clang::SourceLocation) (build/bin/clang+0x5799de6)
#35 0x0000559072cc4c2f clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (build/bin/clang+0x541dc2f)
#36 0x0000559072ce1f6f clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (build/bin/clang+0x543af6f)
#37 0x0000559072cc3b17 clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (build/bin/clang+0x541cb17)
#38 0x0000559072cc33f1 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (build/bin/clang+0x541c3f1)
#39 0x0000559072cc23ae clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (build/bin/clang+0x541b3ae)
#40 0x0000559072cc025e clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (build/bin/clang+0x541925e)
#41 0x0000559072cbadce clang::ParseAST(clang::Sema&, bool, bool) (build/bin/clang+0x5413dce)
#42 0x00005590716c734f clang::FrontendAction::Execute() (build/bin/clang+0x3e2034f)
#43 0x000055907163a38d clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (build/bin/clang+0x3d9338d)
#44 0x000055907179815e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (build/bin/clang+0x3ef115e)
#45 0x000055906e9f2d6d cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (build/bin/clang+0x114bd6d)
#46 0x000055906e9eeb6e ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#47 0x000055906e9ed783 clang_main(int, char**, llvm::ToolContext const&) (build/bin/clang+0x1146783)
#48 0x000055906e9fe821 main (build/bin/clang+0x1157821)
#49 0x00007fc45684618a __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#50 0x00007fc456846245 call_init ./csu/../csu/libc-start.c:128:20
#51 0x00007fc456846245 __libc_start_main ./csu/../csu/libc-start.c:368:5
#52 0x000055906e9eabaa _start (build/bin/clang+0x1143baa)
```

(From https://crbug.com/1432291)
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkWl9z46qS_zTKC5WUBPr7kAfHiXendu7O7Dj37Ly5ELQcdmSkCygnOQ_ns2-BZFsosp2cO3NrqzaVydgCun_966ZpEFRrsZUAt0FyFyT3V7QzT426_WPXcNhdlQ1_vV01KiCLILwPwv3fNBx-3VcDu7amBlBAlua1BUl3EJAHpI3qmEFrFGR3QXYfkLvT_dFjgJfo8O3vdjxrpDbw0ipUNk2NmhYUNRbMvf3F-Togy8eAPNiR9rMb9BLgwil0qhBSYDolUYj6YejlAMNCGhk1oH0YDa6UAMlPaHfo0EOAU6t__K04qEAOl5DG0eFp3n_-sHBrCOJQ0a42R4m-R_q_y5rKLWKK6ifQ6PcnUQNqlZBGyC1qOoO4oFvZaCOYPu_hAMeIOWnXjEXo2ijR1oBe8nSTxted_CGb3-V1LWT3cr2VHbqu9Ks09OW6kfUrutaGB-SeBfguwHc4RAFemV0b4BW9YWyvYfyILEhAFhEOyAKBUi4AkZDPtBa8J0tyjUyDSiGpekU2SEBr0UgU4DzAmaUcZ4hKjgKcHZ0Q4Mz652JsoP3PnyhIHtCf8yCj0CJNLDjZGOhBIiG1odIIaiyepkJVJ5n7fAh83QITtBZ_9H0CnE0ioMeLl-gAGyn4RwfaAEdPoOBnBg-6-BMkD31XFwTWzgCvfm_UjwCv6vp5d92q5n-AmeFrgFdCsrrjcHyw7tq2UbbHkmobgTdPAVkkWWGlcWC1nfsBzmlnGgvUDSOLgCwY1SbA-Uo1OxTghbMiuXtsnC17QAFZLL9__wasUfweWG0t70f4nWzbspEGXkyQ3FvdC61B9W5IQ6GpTSqN4zz_jdZOm6UuRQHGDgpZPr727baRqm23A2mso4Vkza6lRpQ1oN6eKMDYeq-iogZ-07P49fPDYv2AdFfuhEEUld0WKbD02Jh-MqZ18xGvArzaCvPUlTes2R25nFAutO5AB3jl4n1gHpkn6Oc-Kin7YRRlYElpFbSqYaA1cKSbTvWP7UiqdcMEtSGmOok0U6I1A-S1oewH4t2uPWSK8AZ9Vc1W0d2BBAsblZ2oeYBXpZABXv3atBHdDAFKltBUNsu2VGlQiBpkU7edfaIeZgved55MY5tmkrCfvYepK7fHecuhElK8e6oOsyrAJEThSxiGYZIUYRbynFCejyJbv-r-w1eblR3Fj72f8mMnRX_fNNoooLthRjt9NizzGaoDfBe-kJgzyvNjqgswiSZYoiyDOSzfOrkWW0nrf6eS16D0EOjn1dEsA08dnqiLo4QjT3CA88GS_rG-Ya2NrtD9Owgig6CsYnGS5gmtirDP8qtalAFeDeF0CKO-gd3o5ibt4ZVVEXrgYl8mLRhjaLNpzZMCyjc_RF1vxK6twQZ1n6NvArySrakDvBp3u7EBFMcBWWTpUX4yxQwVRooKDU6OdvYGeHXjvr1qDq2dv22jxUuAV66nk4yzgCxGglNfcJzEGUa0tJnDiTK858Q9chLyyGI7SsimEkiRoI2sN3VD-YY3Oyp6Y4V0xtrHO71ltBcXRZmFNOIyn9hKeIU_6J-YV9jzTzEOHpImtErDcRZfw46OZs6n8YrrptHlmE14Sar0GBZ2hnjTFfOK5IzNq33YCbPslAJp7g9FVIDzTrpymr9jjiZJzHLGPADRBECc8WwewKfdDrjN1Vb9nVUBqm_5c7bpMh9JzDOeeXDwFE4R5_Nw7KcjET6e-bZ3ASri3ANEvLgIqxCSE4A-9cXil6FWtFXRqJtb9j43zAWMK5KOjQuX87-BdiXSctTy8NIqV4AskVEduGSf_rOjz3OQxwUkPgfxhIMihnKeg-UTsB9LW5EomCfiX2yrN_qsE-5cXf9lWGn_Q0h-kakEx1B6TCU-UxwyDCeYUkAN2NA0Qt4J-aX9QMDMYfU6jNiYe3rBLpJlGDy7Us-uOKsKnJ6z68szKJvGgf900_4uFeimfga-BvNp19b9duOtty9wsHSb7PH_o16roQ7r6_qLjJU8L_pt-IGxzF9PsoykXt54VACPikpdNWoXkKXdh8hGvu6aTiNJd6BbV5YVQ_dhH3dcd2w1-DDUT-CQLb9_3_O2pHXdWzom_uiVM_ye9c5FTuejzYbHWwvgbfVlmct95lJWcf6rmDvIucjdbIePGzcpMwrC4-SXG_fNHTqszc74No2ff9gUHPqm5BH3c8Kv8VOza5tO8rfG-C2jCf5Bs6JJ-GFakhMVSFdq8xbICMDo6d-62ojP8Az1Hsli2MF-FtqMctilErKkJRlnGox9wGVJ4VQFd7T9mOD2-8wP5Og32fFtLt1Tf84WiGIKXvmH_WoLhyGlFD03go-2jfs98kZBFZCla-1ru0O4MFrXJWU_NpX0q4QjF3-j6sfejm9QgQLJgP8MEoZ4DnC8CftDm7qxJvdxaBPHfODFfukLnNBq3o-qk_8tzNO6qyrBBAz7-HU_nc4b8F4aLxbKKaGV5zq_9IlCWhR0Hv4vpP58XZOSoqAe6HQCuuJhiiw-66aT2KwlHysuR0jP1yJH_9yD1PA32voB_BtVVtY-XywOhzNzQz_Jqrk83Hp-eKVxFMHBUFH74r5Sod6Hxs7D_V7jfND7ZVLIqiI_sbWwXrHKvkF1yjFD8-lyZAT0QqjgvMi90h7nkxIYSAGor3ZHwfy2cJiPlpkQHrX-J90BPx0zHt8z1evFUKTKtVg1nxvmLT4W7r5OnHdZMd0LQHl2j_P_by8Apbd78s9kSZhEZZWiC-XQff_GBHi_mxa6ketXaZ5Aiz_25xzPQgvz8NJSyYGvu7Ip--P5McH_1dH60b0XWCJ3um0ftm9m8sc21n99T94vLe58Bli9_P59Nsb8k2PLGI2Kv8DYb5YgW0ZeKj4vsI2Xl5Tbos8WcgMN72VoVCuOyP2_4ad9MeWi7BBd_dn8h7iYTsbJW7PprLQRKyrhXgO8I1T88jfEOITwZ0yuYYLn7wIxOSXEEY_wfE50BTfMAPjn6p9TuqZa3nOulWWUR9jLYJMTwDjkcOL8Zw3GwjqofrtCzyCeGHsBXlFw8A5biFd7YsZihr3S-at7Qzf6fGn7YzsJud2vlY16G8VvZPLjFrNqTi1E41GfqYF-5MIYZWfMO5aXOOIMe5U3SX3rIarS89Zbs_5NNV170uh1C-wt-CMd-_fZM8Y5Y0TZGdCXi-RpJIyhrhr1jcotfJLiXcQQWqU-MdkkLEgZZReJ-aJGwfFJGlDuxdmUqPN2vq_HWbIXjIHWts0lw8txwcrI20yTfGo-qaKL5g-locfCySny00mYxsPHSSBV5JFQTEjAhMJZEh5eepePyPjXGH7JtJJQr6yMw4lpIU7Om_bYtO4Eqs_C3slwS__RwVczqTYOieIbVPNvVI7bs4Z3NXzatY0ya0MNvOMwK44KnPg2-a8jWUk5e2vTYv14co_1kQOoOCKc-fq9aiJKWUZiL5eulM18kvfF1L58AtZZgy9eWgAcktjLUTHxFRJKcu-02y7dogbVn90x8FQOKDwuJggveoHwgpCce6C85T7KijzyI2tQf8T2fMjo0yNZD_vFMCdQRdEkJMaLewpFhXnKEWPRZkft6NG9lYVS9NWF6pI90dE2eaiFvWf7k4-LmKIoLnnqE5T6mADKFNCelWX06IJvhGy9o3X9GzDTKLtNnQWY-icwVsawzHobdK7EM8yfpsTZBBbP8uHsek_WcFZktTvLF-9Tep6eNMu9I-k4n7gMchwhd83jrKAky7GXveNicnUkjXKKNptalGyjDVVmw2hdbw43SJju3t5xGe7QzA1yNwKz2N3-3CtNwqlSHCfIDbEL4VRP_9EKv3bC-zsrOA_IAh9dk0RzQj1L5oyYFU5SKzw5ysYTt9OSUtRLveA5UtLRgejcjd79NUj_iiBTZbcdbghGMcG4sH674rc2mxT0Cm6jNI8IjsI4unq6JVWcE1JARKu4CkvMOSGsyhnmOQuTsrgStzjEJIwjHGUkw9FNmfG4KuMwKvOYsJIHcQg7KuobG6s3jdpeuSuItymOQnxV0xJq7S6UYzzc3nO3IJf2-5CQqiExHhsU1U_XjbwervnahuT-St26y45lt9VBHNZCG33UaoSp3c31Xmpyj4ZrH4hRbRA93OwU8i_cHrrqVH371y9jOjL-NwAA__8HdkOi">