<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/130446>130446</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Clang] frontend crashes with: bool clang::CastExpr::CastConsistency() const: Assertion `!getType()->isBooleanType() && "unheralded conversion to bool"' failed.
        </td>
    </tr>

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

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

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

<pre>
    To reproduce: https://godbolt.org/z/Khe7cj3Ee
Clang frontend crashes when trying to do int to bool conversion on undefined identifier:

```c
#include <stdio.h>

typedef _Bool bool ; 
const bool false = 0 ; 

int main(void) {
    // bool value = false; // uncomment fix the problem
    switch (value) {
        case 1:
            printf("Is 1\n");
            break;
        default:
            printf("I don't know\n");
    }
}
```
This is related to https://github.com/llvm/llvm-project/issues/108326, which was fixed by https://github.com/llvm/llvm-project/pull/108657. 
But the problem seems to persist when the value to be converted is undefined. Adding back the definition fixes the problem.

Stack Dump:
```
clang: /root/llvm-project/clang/lib/AST/Expr.cpp:1949: bool clang::CastExpr::CastConsistency() const: Assertion `!getType()->isBooleanType() && "unheralded conversion to bool"' 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>:9:15: current parser token ':'
2.      <source>:6:16: parsing function body 'main'
3.      <source>:6:16: in compound statement ('{}')
4.      <source>:8:20: in compound statement ('{}')
 #0 0x0000000003e6b938 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3e6b938)
 #1 0x0000000003e695f4 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3e695f4)
 #2 0x0000000003db5f08 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x000070b139642520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x000070b1396969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x000070b139642476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x000070b1396287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x000070b13962871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x000070b139639e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x000000000765dba0 clang::CastExpr::CastConsistency() const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x765dba0)
#10 0x000000000765eb1d clang::ImplicitCastExpr::Create(clang::ASTContext const&, clang::QualType, clang::CastKind, clang::Expr*, llvm::SmallVector<clang::CXXBaseSpecifier*, 4u> const*, clang::ExprValueKind, clang::FPOptionsOverride) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x765eb1d)
#11 0x00000000065bd8b1 clang::Sema::ImpCastExprToType(clang::Expr*, clang::QualType, clang::CastKind, clang::ExprValueKind, llvm::SmallVector<clang::CXXBaseSpecifier*, 4u> const*, clang::CheckedConversionKind) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x65bd8b1)
#12 0x0000000006d820af clang::Sema::ActOnCaseExpr(clang::SourceLocation, clang::ActionResult<clang::Expr*, true>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x6d820af)
#13 0x00000000064aca72 clang::Parser::ParseCaseExpression(clang::SourceLocation) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x64aca72)
#14 0x0000000006527bd3 clang::Parser::ParseCaseStatement(clang::Parser::ParsedStmtContext, bool, clang::ActionResult<clang::Expr*, true>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x6527bd3)
#15 0x000000000651f253 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+0x651f253)
#16 0x00000000065208e0 clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x65208e0)
#17 0x00000000065217d1 clang::Parser::ParseCompoundStatementBody(bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x65217d1)
#18 0x0000000006521ea4 clang::Parser::ParseCompoundStatement(bool, unsigned int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x6521ea4)
#19 0x000000000651e957 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+0x651e957)
#20 0x00000000065208e0 clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x65208e0)
#21 0x0000000006523148 clang::Parser::ParseStatement(clang::SourceLocation*, clang::Parser::ParsedStmtContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x6523148)
#22 0x0000000006525a7d clang::Parser::ParseSwitchStatement(clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x6525a7d)
#23 0x000000000651f4a7 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+0x651f4a7)
#24 0x00000000065208e0 clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x65208e0)
#25 0x00000000065217d1 clang::Parser::ParseCompoundStatementBody(bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x65217d1)
#26 0x0000000006522fba clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x6522fba)
#27 0x00000000064347e3 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x64347e3)
#28 0x000000000646959d 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+0x646959d)
#29 0x000000000642851e clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x642851e)
#30 0x0000000006428cd9 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x6428cd9)
#31 0x00000000064304b3 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x64304b3)
#32 0x000000000643138d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x643138d)
#33 0x000000000642381a clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x642381a)
#34 0x000000000482f028 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x482f028)
#35 0x0000000004af7965 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4af7965)
#36 0x0000000004a7b13e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4a7b13e)
#37 0x0000000004be662e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4be662e)
#38 0x0000000000d522e7 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xd522e7)
#39 0x0000000000d490aa ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#40 0x0000000004877429 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 0x0000000003db63b4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3db63b4)
#42 0x0000000004877a1f 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 0x000000000483a1fd clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x483a1fd)
#44 0x000000000483b27e 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+0x483b27e)
#45 0x0000000004843195 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4843195)
#46 0x0000000000d4e583 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xd4e583)
#47 0x0000000000c16164 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xc16164)
#48 0x000070b139629d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#49 0x000070b139629e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#50 0x0000000000d48b55 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xd48b55)
clang: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134
```
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzsW1tz4zaT_TX0C0oqErw_-IGW7W-dzNbMjl2pvLlAoiUhpgAuAPqSX78FgBIvljV2hpNKasc1cWQSaJw-3ThokBBRim04wLkXX3jx5Rlp9VbI8z-ZFnzz51a0IFl1Vgr6cn4nkIRGCtpW4IUF2mrdKC8sPHzt4euNoKWo9VLIjYev__Tw9a9bSKs_wivw_GJVE75Baym4Bk5RJYnagkJPW-BIyxfGN0gLRAViXJtPpRA1qgR_BKmY4Ehw1HIKa8aBIkaBa7ZmIM3ovv2X-O5fZf7AIeNV3VJAXrhSmjKx3HrhlWuqXxqgsEb3F2YMO5AXXiDPLyrBlXZX1qRWpvcl8vd3Pb8w4HaEcQ9nj4JRD-fISy88v0AIIUeD6_5I6tZ1t4asBXe75ZXY7YBrtGbPSG8BNVKUNew6K-qJ6WqLzAjGxngI81MRBShwjqPBTyMZ12sPZx7GNwoFXrziHsYezr3wYtK2lEAexpcprElb62_YRVRwD6caPXDxdGwEL700VLnf-5h4fnG3ZQoxhSTURAM1IZ6kD9PbtlxWYufh67p-3P9v0UjxB1Taw9dMqRaUh68DPwtx4uEVetqyaoueiDJsAkXly8fNNm1dO6NJnC5NpC9aPYwMUgA7ZSA3JhuV7tJ2C12cTb5Cl63GOab6ZF2iglKT3iWpHmwfe4Npk9UGtBoOtXR5dqtN48t213QJPmCyMjPJTD8PX0sh9GuHXAt8XbPSw9fF7Z2Hr6-eG7msGmMvyKPc9HdTrLPmhcWKKG2a9X-tBDfuAq9ebPxzZGeI6VwoBdL6YFDhYAP67qUB12zhhVdMmekFhPeXkWeCliAP45ZvQZKaAh1O8m7e25xK0ZqwGqhh5Munq-L2Cqm23DGNCCrbjVEiIfX35REinKK9UpgoWFmykdKSVGAyrLGSV4FSQJESrXSXTU-ilKiYTWfZcqQqyRq9PISPHsLnLz0__yLFRpIdInLTmvmvuhiKxsZM7BpWg1zAc1MLCXIfxwXZM60WWrb8wcPXpVEgdxstNvSJyPUiQosNWghjkTSNsdvqptVLhRY74z9aLJ6zZEHUbqFeuCbPXnjJuIYaLdZcLB5BlkKBuY8Wt2ix2FTVQgtRV1ujd-HlSaSmseKkUVuh0WJdiVrIBWVkw4XSrFJuDMvu6LJRZ0epFefA8DS6FhYmVYPYcFW1UhrdbIhUIJEWD8CRh1Mb-tTzC3yke2K6m1-2m5mH65ZXNnHNmmb6O0E3BsKTBhhHxnfRcoqUJhqsitvUTo1Ep5fmA849v4iOGMq8sMD-Bw0hD4c-8p_9_U8ISZmHGbKZbSeqelHuwxcj1Db17lzyZn0jSZ7uhdISyM5zysm4dlMy--4c9PCF_9wB62EHE9h5vI6OwV4ZkWibz_yWbTipPZy13JYkFNXCGJ8XpIHRg8QjkLSM136GViZPv0IlHkG-OFT_RTitzVhZx9uozcpUNc-601ff_ufsh5391C-DME8iHGO_c8ep83OW3CfRoma8fV5seOtuVEsllomFbLv0gKOxwTzJ1xVq9FYCofcPrK4_Zt32763HU7hRmqCNshR8FHaUJr3hZGwYZ-k6RKQ0Cv4hs7ZjbzZ9ZTYoP2wwKHuD2dhgmEOefMyg7dIbzIcJliYxLYn_lxbd-SZBh8JhNBPVn2CEMqBDjDe7pmYV0xOsEog2KjNoWdzedXOhqxSc1gxa_E9LalcRrKY0_Mo4nVy2o-HCXO2V43ZH6vo3qLSQXrgaGvn99wui4LaBym0OXM-o9cKrPZ7iyAi_mSLuyOjXXz43lsrPjyAlozCrFnVE92EYCWYSlzQrgyGcW9iRQ0D2sbgTXX11nLXvYn7Eyw_if7WF6gHo6lAEuvFm5Lljsud5pPkJzbBP1sd5Lir9ma-IAsfokONbu7J_EhUxo0-cKmyB8RWU3VCtjodGy9ZWBrP66rzpfQ1HvkakIikeIv1ia6nB5723oJT165TPcwJ30Hrg0Xgy4LSk4TeB3-6LqTHuV23prd7pTqhMKNym4x8SQudrz0Q8ZiJY4_g0EwcWPstLqGoibbiKtQZZaC1Z2Wqz-8neMaMNT52vIW6tq1NB_ya5JxJoKgau_xDk0dGmLWZl3_Lbs59M8tDPwP8L7P9T6J43UQ0ZPVXphKogpcHpKdttgg6UXQhqah43HeeFasD0ULMpVCDRx6AeYK7QYbsy95aqA9bDzidSAHmc_pSCHycFht8D-9j_KQXvlAI8KWXNep69j6rTFcfRLHmbgnldNE70LuKJizFJ6WkX7YP99zs6L3gDrwcfTmuKiPwUkh9ZU0RkICTT2vankLwpJPG_pqbA00oRr0tyEup19yB6CnXQx0T7Hap3Wwmzr587ba0LvYPj-i4KoxROb0T2Dl4eXni93pcxvtmntJDvSc072DU10XDD1-Kth0zDXp-Ihn6Gf2LdQ4hZ966Wip6ocXUZJXmcn14aDAP_kaJt3uTntoHqtZ89c8cn6zu1701-X7f_yIJ8LeRXwjdww9kP4Nyy2nM-Lo0jnMUBfJPzz3KQojdcg3QvIL5_-XjV4mQci6oCpQbPzWZlynJxYGr8OsncrWj-Taa6JWdE2Jtzena-pln2o_mqaN7zFUxkz4_K07J39ewSabxU_w0czatpxs-eBTxhIQiz05p2J5pP8Ai1W8KG7n9uyP-28EVPCpWDCH6F9dEypX8u-9-CtjXc7BohtV09Z1_7nIO9-5PnqDjMgteLuz1pkU0ROz_2Dwvmr0McmB7qqLqMMrz28WjvtRIU_gPcPeDcP9KEqtXQXdqf1ZgJYAehBziq6SKyTvMkHr126Q6JHUE4OzY3eo8tGWNLyyCEMXlutBuuNOH2GNwR_t52ZuY87RD2-Ec1WlRCkmAYv9axSHs3Hg9LeXbKzZnlpUPW4x6VTD6NMYYUVVVw35226zc6hZTkxUrEqtoS2b9XMpKxQuNreIXcOb154Tt8Pfp8jD7KfULQnupVcGfn_PHN2s2uqY-6koxfuhkbr1-t5ohK9ghycvLAw2Hkj2UgTSOcWzIGRvdHYe6l5dPedVPMHVnxwqIidV2S6uF-zcdy7Qbu0mUVrMRuRzidztajcVO6ayfs61ViCBiQoyXjm24RcEE9dLi_r56fg8D9URLFqntlm3cUjhqbC_daEqbV_vbEHKlrk_5uy9zdN02KXqmL4ak3z540qsmupMQe0dlThbP9UZVfRHkkGMHkmEkSlsOzMMcOk7g7X1t-S9ZQv4y4PB23WQ_MOKyHVI_wNK1IMHp5-v8uLQzXy4ZIvfTfjn84Zi0kwZq-yZqNF3m19u2pHAn1pKNp8Nam-ETTYlSkzH7gpHO4T6JJiRKWOIWP0vGLKNXbXPwiSrPVH3FxSn8PsW8IM2G3r3LeT1-XID-YRENTT-K4jMqiMMjjtwBfDj6PSoAja_9b5P-NJM5afVpietqSyVoNcdZt5_a1xh62FY7i1fGjt1bi-aoLi6lHPKrp_CpIgiSy30KYb0hntB9ycgwO5zT_4LFF26U3mE8NQuSj-3vT515pIvX9wKF3DwFRP0TsTwKblXGMnPE5Y2PMukH3eY1ASrNWFC6NBl9y6TLcHWRHT0xvETwzkzYUUBBGBlerAC0ekRZIASA2KMjNGPtCHEnQreRgJpjpOfxOwBk9D2ke5uQMzoM0CqI0TaLkbHseU8ixH2Q5LQlNksjPaVXSFKIyxlW8hjN2jn0c-6GfmTTDyZKUPlRZHFcQrYMwBi_yYUdYvTTpvxRyc2bPzp8HoR9FyVlNSqiV_eYQxh1J2Isvz-S5PXJfthvlRX7NlFa9Cc10bb9uZL8T5MWXR74WxPT2X_QVhbNW1uff8XUWx-bjOf6_AAAA__-FFZsi">