<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/150403>150403</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [ObjC] Assertion `(GC_L != GC_R) && "unequal qualifier sets had only equal elements"' failed.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          k-arrows
      </td>
    </tr>
</table>

<pre>
    Reproducer:
https://godbolt.org/z/nEKK8qrbT
```cpp
extern id p3;
extern __weak id p3;
```

Backtrace:
```console
clang++: /root/llvm-project/llvm/tools/clang/lib/AST/ASTContext.cpp:12089: clang::QualType clang::ASTContext::mergeObjCGCQualifiers(clang::QualType, clang::QualType): Assertion `(GC_L != GC_R) && "unequal qualifier sets had only equal elements"' 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 -x objective-c++ <source>
1.      <source>:2:20: current parser token ';'
 #0 0x0000000003fcfbc8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fcfbc8)
 #1 0x0000000003fccff4 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fccff4)
 #2 0x0000000003f117c8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007e7747e42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007e7747e969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007e7747e42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007e7747e287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007e7747e2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007e7747e39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x000000000753d175 clang::ASTContext::mergeObjCGCQualifiers(clang::QualType, clang::QualType) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x753d175)
#10 0x0000000006a22aff clang::Sema::MergeVarDeclTypes(clang::VarDecl*, clang::VarDecl*, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a22aff)
#11 0x0000000006a3cc88 clang::Sema::MergeVarDecl(clang::VarDecl*, clang::LookupResult&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a3cc88)
#12 0x0000000006a3e0ba clang::Sema::CheckVariableDeclaration(clang::VarDecl*, clang::LookupResult&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a3e0ba)
#13 0x0000000006a42ebd clang::Sema::ActOnVariableDeclarator(clang::Scope*, clang::Declarator&, clang::DeclContext*, clang::TypeSourceInfo*, clang::LookupResult&, llvm::MutableArrayRef<clang::TemplateParameterList*>, bool&, llvm::ArrayRef<clang::BindingDecl*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a42ebd)
#14 0x0000000006a61f7f clang::Sema::HandleDeclarator(clang::Scope*, clang::Declarator&, llvm::MutableArrayRef<clang::TemplateParameterList*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a61f7f)
#15 0x0000000006a62a00 clang::Sema::ActOnDeclarator(clang::Scope*, clang::Declarator&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a62a00)
#16 0x00000000066b1ed3 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b1ed3)
#17 0x00000000066c1169 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+++0x66c1169)
#18 0x000000000667eb3e clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x667eb3e)
#19 0x000000000667f2d9 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x667f2d9)
#20 0x0000000006686fda clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6686fda)
#21 0x0000000006687f75 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6687f75)
#22 0x0000000006679cda clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6679cda)
#23 0x000000000497c238 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x497c238)
#24 0x0000000004c6f0d5 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4c6f0d5)
#25 0x0000000004bebf0e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4bebf0e)
#26 0x0000000004d62e01 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4d62e01)
#27 0x0000000000da218f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda218f)
#28 0x0000000000d98dea ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#29 0x00000000049e3409 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
#30 0x0000000003f11c64 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f11c64)
#31 0x00000000049e3a1f 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
#32 0x00000000049a5e2d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x49a5e2d)
#33 0x00000000049a6ebe 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+++0x49a6ebe)
#34 0x00000000049af2d5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x49af2d5)
#35 0x0000000000d9e63f clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xd9e63f)
#36 0x0000000000c52774 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc52774)
#37 0x00007e7747e29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#38 0x00007e7747e29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#39 0x0000000000d98895 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xd98895)
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/eJzkWl1v2zrS_jXMDSFDomR9XORCdeK-PScH7ZsU59agqJGtRiZVkkqd_fULknL0ESdt9sTFAlskhSKSw-d5ZjgcSqJK1VsOcImWH9Dy6oJ2eifk5b1HpRQ_1EUhysfLW2ilKDsGEoU58vOd1q0yl2SNyHorykI0eiHkFpH1vxBZ8-s__0y_y-Ir8nMU--6HtS3yczhokBzXJW5DFH4Y7mw2P4DejxueRpprP_9A2b2WlIHDMNgVXIkGkJ-zhvItIh_MT5hjRNZSCI3Iumke9l4rxTdgxz8RWWshGoXIuh-2buoCkXV-99X9vxJcw0EvDO4wD4ifZsaq6x3mKMz_v6PN18cWxveGge7vPcgtfC6-rT6uTPe6qkEqRNITZhBZnbKOiJ03VwqkrgXHhjZJP642NxiRAIVX-ONqc4tIhhGJEYkxIqTj8L2jDf5-nBMr0ArvaIkFbx6xa4UG9sC1QoQgkuCK1g2UC-TnX26u87trrLpiX2tMcdFtsYRWSI21wDP313rXFQsm9oO0M8FrpTowUmPKS1xz1nQlYL0DzCRVO1w8uZascCtNtDFQCkqsRCfdbTOSKiVYTTWUWHYcKybrVhu8d5qye1x2-9YFh79AfvZFiq2ke0zltnM0XVCI1mBiYt_WDUgPDm0jJMhjJHj0qLTytOz4PSLrouZDoJj4wt62_EFl5UXY22JPGLu0bY31TredXijs7Y0K2PMOaexRtffUI9f0gMKrmmtosFdx4T2ALIQC0469O-x5W8Y8E5hsR2uOwqtX8ZrOitNW7YTGXsVEI6RX1nTLhdI1U24Oq_H09gGLwvimfgCP9YxQuOrVDq-RnwdGwsm9MCfm17eroJMSuMYtlQok1uIeOEYkMSuXJMg3Qoc-9g_-8V9YsapgKbYRYgNcPSp38UXWXFsXfnVBkA6dJP2xEUpLoHsb3Stcc-1iPX0nXyLywT_08Mxic-CDGXhWVdEp8KsGKO_az_yu3nLaIJJ23KbUEjfCTHEOqAbMAJVMoQZBwlK8Ml6_BSYeQD46bP9HedmYGdNew0mfab7z7a-zH_b2E0iSKIGILInfk3I585DGmzjympp3B2_LO9fAFkosYgvZDhkAR1ODWZxVDLd6J4GWm_u6ad5m3Y4frC_ncKMkxltlJXgr7CiJB8Px1DBJkyrEtDBZ8U1m7cDBbPLMbFC82WBQDAbTqcEwgyx-m0E7ZDCYjQMsWYZlkCzPvum997LpcTtWZoFP0lNMCaFVNcZyB3vqrv4yfP6m8gqYRTfj0rcgks_YTBsKIZoz8OqRD7yCKa-QsTT9Oa9fpHQjxH3X3oLqGm0T8hn4WMQDHzLjA35BT_NZ7YDd_01lTYsGDH4qqZnyv4mbQT9wC6fcIgJFeZpbzvRnPucm5JTaHRNm7cyJjbvHJ9qOi_fZQBPsd7YA-MQr8QuKrUZb5F-dNlhzKenjLVQoXI0tw75tqIYvVNI9aJA3tbIAwuthrcwMnrb0oeZlzbdHl5rxZ_Cb9czgt2jqtziokhdyh9t0_6nD3kPVM6hieQ-qLGeqEOr7r0TzPxPlHHQM4IFOPKETFwGU4RjQF1v8jq5HKSevNMgBcc7LXGtZF52e7x6vLc5nM5RHD5v1iM3RV78-ai3kLeVb-MRrt77fXzYnzCBbMpWNBUGc_VS2j1J07VQY09Yv7LsW2OnU5ZR7SmDPdZjo_jZ9n_d3ufBGsH5bmYfo71beajson06VT6AI4afKf5brjjMz3xVUn7gG6Y4xbxfypz1e9WbOzJnftNl68Sx6WUUGvbKZXhUpfx6p_QKfyFbz-nmdcRbV5hH3W1QzujypRqZ1c5zGVUlfVe364ILqxYrsXEqdQQvLdtAimGmRVNOT0TMtvor2Bh6geV5yf27p9w6-aDnd0p-So93sr0_kpKGcF2XXwKd9K6S-01TDmfZJR3MQgcyWUcZOBIR9rprOcTs2rto73wnJQRoAT6ruKEuYOTOPoK1ECR-B53Z5u1vXB2Cdhv6WwffuMHsgA8xJkRmxuPLLSXCtpdn2eHkC55kQOgwDwknBFxVQVD5MhXRzfuJKU-4e3T_X8mVKZ4nfHufAYlLnRWVMwA_GLHq8A5mHpwIgfY3sWVJQj29APym3_JKSIK0wY8FmT42B9PT5aUflsXw8nrmm98gKP4i6PA8Jh3LgkE45ZGkJFB9lXwVfbV4YMbnb06b5G5gW8tO-bU4Smp2bjI2-TBzVzRkuZf0AcvbU02DKpkkCwsjPrCQjo1VfAmykVdW2uqXnHpijMGe0aQrK7jcVnyZ2N3EfOqtgJfZ7ysv5Kj7pPaX7fqI1s1MjwEgcLWu-7bcL59qnAZsNOxyCwP1RUFWzjbLdewknnc2NjZa01urYPDNHm8YsBSFH7abL6HmXDR8nuB2CSNLQfWHScTJIRdLjw_I_RPHcGfNXCUHA4vHT-FMPsl3LbcfvaAXN40TL1_12jkf2FvFTwE_fLpjgosHk-cH_XHAYxRctlXrhvxwFZKoaXQIpX1TNeo0-2xmPUk5S92yg6fDS4fqVrvmknBkRe98qwdIeQmlWzNAYCnirKH-IQr2syB-iuKmVnijyWi5-ioCW1sb59m3Tr4vYh8lvkdKINUgZzaSsyLTgGsO-Gl1PCoQTlcFLLviNUp6hWrXyDOItZ3s4xGGf0o6VyBG8TSV5nwh-vkO_d-1hkQ24J9Wfz5YkSSJsEL_3xM70MPH8vV9WZm98rWqHDAbTuUGIfLzZmDEbpanUmxGtX54CotEU2bxQS7Mldsbf30_GuJt63BbmGKQ0u0r_MQ6u-kMDZn38uw9Z8I9a7zAcahNOJeAgjAzGTgH2HrAWWAHgelTMm5mORTyWoDvJwSw_M3L8xdFFeRmWWZjRC7gMkmUYLpeEZBe7SwhCWiakiIKyykgChBVFFhKIsyph_jK6qC-JT5Z-QqIg8BM_W6QFLYHSMFumEIdhiiIf9rRuFmZZLITcXthvZy6DpR_54UVDC2iU_VaLEA4_sG1FhKDl1YW8tJ_dFN1WochvaqXVYEbXurEfeX0uvq3Q8uo3fk900cnm8j__Zqin_nBJ_h0AAP__c_rl6w">