<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/150738>150738</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] crash on invalid lambda default argument in templated function
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:frontend,
            crash-on-invalid
      </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/fazvEf459
```cpp
template <class T>
void foo(T x) {
  [](T=x) {}();
};

void test() {
 foo(0);
}
```

Backtrace:
```console
clang++: /root/llvm-project/llvm/include/llvm/Support/Casting.h:578: decltype(auto) llvm::cast(From*) [with To = clang::sema::CapturingScopeInfo; From = clang::sema::FunctionScopeInfo]: 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: /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.      <eof> parser at end of file
2.      <source>:2:6: instantiating function definition 'foo<int>'
 #0 0x0000000003fd9768 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fd9768)
 #1 0x0000000003fd6b94 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fd6b94)
 #2 0x0000000003f1b388 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007e29e5642520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007e29e56969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007e29e5642476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007e29e56287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007e29e562871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007e29e5639e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x0000000006babb8e clang::Sema::tryCaptureVariable(clang::ValueDecl*, clang::SourceLocation, clang::TryCaptureKind, clang::SourceLocation, bool, clang::QualType&, clang::QualType&, unsigned int const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6babb8e)
#10 0x0000000006babfb8 MarkVarDeclODRUsed(clang::ValueDecl*, clang::SourceLocation, clang::Sema&, unsigned int const*) SemaExpr.cpp:0:0
#11 0x0000000006bad502 DoMarkVarDeclReferenced(clang::Sema&, clang::SourceLocation, clang::VarDecl*, clang::Expr*, llvm::DenseMap<clang::VarDecl const*, int, llvm::DenseMapInfo<clang::VarDecl const*, void>, llvm::detail::DenseMapPair<clang::VarDecl const*, int>>&) SemaExpr.cpp:0:0
#12 0x0000000006bbd2e9 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
#13 0x0000000006badba9 clang::Sema::BuildDeclRefExpr(clang::ValueDecl*, clang::QualType, clang::ExprValueKind, clang::DeclarationNameInfo const&, clang::NestedNameSpecifierLoc, clang::NamedDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6badba9)
#14 0x0000000006bae39f clang::Sema::BuildDeclRefExpr(clang::ValueDecl*, clang::QualType, clang::ExprValueKind, clang::DeclarationNameInfo const&, clang::CXXScopeSpec const*, clang::NamedDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6bae39f)
#15 0x0000000006bb3f13 clang::Sema::BuildDeclarationNameExpr(clang::CXXScopeSpec const&, clang::DeclarationNameInfo const&, clang::NamedDecl*, clang::NamedDecl*, clang::TemplateArgumentListInfo const*, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6bb3f13)
#16 0x00000000071e30e2 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformDeclRefExpr(clang::DeclRefExpr*) SemaTemplateInstantiate.cpp:0:0
#17 0x00000000071e324b (anonymous namespace)::TemplateInstantiator::TransformDeclRefExpr(clang::DeclRefExpr*) SemaTemplateInstantiate.cpp:0:0
#18 0x00000000071af589 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#19 0x00000000071b6139 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformRecoveryExpr(clang::RecoveryExpr*) SemaTemplateInstantiate.cpp:0:0
#20 0x00000000071af834 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#21 0x00000000071d8355 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformInitializer(clang::Expr*, bool) (.part.0) SemaTemplateInstantiate.cpp:0:0
#22 0x00000000071d8ee6 void llvm::function_ref<void ()>::callback_fn<clang::Sema::SubstDefaultArgument(clang::SourceLocation, clang::ParmVarDecl*, clang::MultiLevelTemplateArgumentList const&, bool)::'lambda'()>(long) SemaTemplateInstantiate.cpp:0:0
#23 0x0000000007f46071 clang::StackExhaustionHandler::runWithSufficientStackSpace(clang::SourceLocation, llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7f46071)
#24 0x00000000071aa937 clang::Sema::SubstDefaultArgument(clang::SourceLocation, clang::ParmVarDecl*, clang::MultiLevelTemplateArgumentList const&, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x71aa937)
#25 0x00000000071aeb9f clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#26 0x00000000071af98d clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#27 0x00000000071dbd16 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCallExpr(clang::CallExpr*) SemaTemplateInstantiate.cpp:0:0
#28 0x00000000071af4d2 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#29 0x00000000071f2d17 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformStmt(clang::Stmt*, clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::StmtDiscardKind) SemaTemplateInstantiate.cpp:0:0
#30 0x00000000071f339e clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#31 0x00000000071fca54 clang::Sema::SubstStmt(clang::Stmt*, clang::MultiLevelTemplateArgumentList const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x71fca54)
#32 0x000000000725cd20 clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x725cd20)
#33 0x000000000725a9e6 clang::Sema::PerformPendingInstantiations(bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x725a9e6)
#34 0x00000000068307c2 clang::Sema::ActOnEndOfTranslationUnitFragment(clang::TUFragmentKind) (.part.0) Sema.cpp:0:0
#35 0x0000000006830b42 clang::Sema::ActOnEndOfTranslationUnit() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6830b42)
#36 0x000000000668d810 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x668d810)
#37 0x000000000667f4aa clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x667f4aa)
#38 0x0000000004985888 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4985888)
#39 0x0000000004c78555 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4c78555)
#40 0x0000000004bf538e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4bf538e)
#41 0x0000000004d6c281 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4d6c281)
#42 0x0000000000daa6bf cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdaa6bf)
#43 0x0000000000da130a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#44 0x00000000049ec839 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
#45 0x0000000003f1b824 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f1b824)
#46 0x00000000049ece4f 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
#47 0x00000000049af47d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x49af47d)
#48 0x00000000049b050e 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+++0x49b050e)
#49 0x00000000049b8545 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x49b8545)
#50 0x0000000000da6b6f clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda6b6f)
#51 0x0000000000c5b964 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc5b964)
#52 0x00007e29e5629d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#53 0x00007e29e5629e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#54 0x0000000000da0db5 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda0db5)
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/eJzkW0tz2zgS_jXwBSUXCfB58EGW7NnMJhNv5MnOzQUSoIw1BXAB0JHn128BJMWHZMdKSVObmq1sjYxH4-uvG91NECRa87Vg7AqE1yBcXpDaPEp19TQjSslv-iKT9OXqC6uUpHXOFMBz4M0fjam0_YluAbpdS5rJ0lxKtQbo9k-Abgvy5_NNEYQp8OYg8pp_eVUBb27YpiqJYRDgRV4SreE9wDfAmz9LTmEhJUDJPdwClEIQXwNvDmGDzLYDvNz1xLYFoBRgO8r-2fxoJRmmTTOgk9PI9kZTBvCaudckfzKK5KxRtAcvhZYlA948L4lYA3Rt_-E5BOhWSWkAui3L582sUvI_LO_-BOiWi7ysKesbVnVVSWVHLIg2XKwvHwGeh3FipVGWl-alYgAlpDbSonfT8BzgeU6cSrdKbgCaO83C62_cPMJ7CQFewgaaG6vZhjS_FqQyteJivcplxT6IQgJ8Da2Q1-fc1iI3XIp-Sri08OZaM2U7IIg8rgnAi3tpzYeSr6R0iFAEUAQBQg4tXty_NP22k6h1vWHCQFlALnK5qYjhWclgo7IPEAIohgXhJaOXwJvffbyZr26grrMNN5DArF5DxSx90Eg48UJuHuvsMrfkdFxPTMK1rpkG6BYSQWFrGWgeGcwV0Y8w2xkfLWClrNPnTGtGoZa1aprtTKK1zDkxjEJVC6hzxStj8a4MyZ8grTdV4z7eJfDSOyXXimx22uvWbWRlMVkWeMnUjG2rUiqmbJu1yYx0ZOuZUbV4Aug246LrbjwQztb0G1HFLICzNZxJK5dUlZVem6o2lxrONpYFOJttk2hG9GamX4QhW4CXXBhWwlkh5OyZqUxqZvvhbAVns3Wez4yUZf5IuAB4-SZeO1gLUulHaeCsyGUp1YxyshZSG57rZg3H8agZ4EVLrIsAvmUL4AWTBcA3sCJKMwWJgUxQ6zIFdxsQtcP6qXiOAJ5HllcutCHCcGJ3FixaP4aUFVzwxnNRbCMBXnBhnGvGNjgAhD3obb3uf7igaRwlg92nX3Tz405xYZyl7xtfSfpBinx7kNooRjZuJyygXcXti-REJgfo2tu28Gwsa8D7E_BRlgaHwC9KRkRdfRYrvhZ2yya1cAmAwlLaJc4B1YLpoaIxVD_DSQIX1jm-sFw-M_XSYPsHEbS0KyYth6MxCykM25pLm1Xw3HP_b-TjVn7MUMrCKEAh8lqlSp4BdLtNoocomJVc1NvZWtRNR36p5WXkILspPeBgLDCN0iKHlXlUjNCHJ16Wx0l383vp4RRuEEdwrR0Fx8IO4qgXHI0FoyQuMCSZDZ5HiXUTe7Hxnlg_O1qgn_UCk7FAnLI0Ok6gm9ILTIcOFmUkyxI2zHOrXZ4z6qVJj-wrUZxkpd3Ng5FfSVmzJctLl28XIyEu-nyUObGbYNJ5v5P7Ty7od2dmUpaTQf-qSXnvsmL0ds9u-3JhoK1STFcbnHYbtzw2LNuA401ZLrIEfiLq6StRlrLPyy-_a0ZPQ6gz2XcUtmNutpWahASL1Z9gpaGH4FIO0H5hBVNM5FPAg4Xfi7WVuK-hBde29pF5yYRmn0jVlMMTGQP92kxyaGpT031vuq2KXb4biqDMEF6Oxd0Rrt6HxqbeG8fOm-yjMfsZRSx1nmLHn5D477Le7bO_Fft46vsZSQ9Hw-ual7TdDA1r79y6fUjaY97NOhAErSCinBV_Ixv3jNEpOLX5b0wbRu2oVcVyXnCmPsp8OohsGP2RSN0-js7b4vwj12YI5kyh1BqhD6XBxEQMp8VPZaLFH3-4R0VroJGf_rwWsjboLRROQhgufPwdCw2o27fUIcKmpB6zRV7n9o2udzDbxcwzMOw47BmOhgzHPsMeQ-OSirF7RYQupNoAvAAoIUKKl42sNRRkw3TlHsbSsW4fds-DUjWPik5WK-fVnTTq2FUX-0LZgYAbTzVBgSuQj4d7fqzJGCspwiQ9O-v7KvwQ9nSMPYt8fH7s3ePnvg7jnuN0Qd7UDgkOfhI7IH-MnSY4DM-O_YPghpOS_8leU2EUui4rosyld5xiaKoYY5Er5AYlXHfC9KBYAfDC9Xbn0jfdsW1ZZiR_eijEuLDrk8aqzrRZsoLUpemi8aQcfitF3hG1efWp41NdGv6RPbPyULwfZZSWsGYeQHFJNhklAMW9Rijpjonez-OoAo2LIPJif5Q8DcmfbraPpNZWue7cpzlQq8W_uXlc1UXBc87ag7dV4zFvE_ReI50-ubU67pIbCibbm6Q4Plw-_H95wsmJaVTviQknxLBsXPmeJXZ8dG69H_2G7UfGwGgav9OE_izxe1Kv0Iz60dmxL0hZHiiLd61H6rBXxwT0_NXjifif1DEFon58duwrs5nGFdey94xwwsXtCkuuc6Jo87h5BEt4UiEVGKfs_F4qN5WsBd1na9wzKjfer9OkcipyEgZvpIX32uzdcf4M8d3psIvv43c9MQpzirzDGg6Y6t4-L3cv7Y7IgP3kXQrsjv3G_z298o16vfJ4ojxJWXRY-TumrLvdMUG5WPdU2FUBSs4P3ELrgY_PoxLsxTk6DHyem8_iRtDPhdszpYP8u-DmVpH1fu1y_3vX3gWA_dr8wD4Jp3iy4Fg83VWQE59iNFh65kZ1QBQlNPG9SX2mu9LW_b6XldupjbsOufpckf_W7M5MToPtwF-UrKsvtpa9OXBEviPjk6R1yT5sKqls2WzYeTZ9q2ZPQjwmIS4CQvZImK_uXz3wP7O_t5B6wKPqIUiTMEmS0fGmpOwXJuYusHSZnuW1YW3TWZyrBdLDHBUKQR4n4fhB-1ZJYZigB3CeCWGDYYcwGCXpICtCPH7zumjXbCJcc8lqn8vXVTqL_7Y4ey1GaTmgUY4Sf3xo7vD2yjzvUtG0RBgpe5aj6hZfj36Ucj1KSJQVMM_9hw2xAgaXVeZKkRcXRhb5I1H9sW_znmrc1r3DOosSDcpeBzzRwccegR3tC__exYWBJqsNKcuvLDdSfdhU5UGFovGZgJXR3iEZVURU8Wd24D1aEIyDBMsTnJ7yNKhZuHWdhb-Qmw0RdLqLD1pPm3acrOzqxBIwIMcoLtZtumhMu5vw8JBvt77f_JERzfMH7Ya3FI4G24YHowg3uuueiCNlabeCVIN-O2RQhjn3aQh_1zHTrzI7YIxweocoQcPrToduCrWntLVYkYKVLyMu_-oDohZx7_DR1LlYMDoH-ds5x6QwPOwF8Zg1UgQxfZU1ZzWylxk7KkehezLRDnjt1dsbQ-eTw7SdYqetEpzavStNipnMCz12LCm_yky_zsivMts7MHwrFu88oGruNrRXKd5LYn_P4exUOrJ6KtMJlUkYhK_BXg5-jwqEA5XBayb4C6k8Q7Xq6NmRF3qTHB5lURvSukqkA-9CyXzvZtRrGfrktYdF1uMeVX9eHmZpFECL-NQLN6L7hdHkYmVK0yPvrbopvUA8FcgCDz482DkP2hBlHgZqvXsJFgyWCCZG9mgWwkb46e1khTdLD_vwHDKl3Ovyxr1g0T40wLz1_-aDAug-lWBbbt2JMujjwGKsNYOzZ2gk1IxBPijm7UpdEQ8VM7USzG4_O3P4bcgFvcI0xSm5YFd-HOLQC3HoXzxeZTT1Aw-jKKcFRT7DeZZESRpRP4sDlMQX_Ap5KPRiFHlBkPr-JQoTEmVx5OEoShGJQeCxDeHlpd0Wl1KtL9w3DFd-6MU4uShJxkrtPt1BqAsCnfrua4qF7XAX76WYcfFMSu46wuWFunKfR2T1WoPAK7k2ul_GcFO6b4IaqeGy_URCCthKgU3ZBmnzsqr_uIML2H3kQ3c38C9qVV79-Acbrb7PV-h_AQAA__98YE_W">