<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/125359>125359</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            ICE on lambda expression with concept constrained template argument
        </td>
    </tr>

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

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

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

<pre>
    This program
```c++
template<class T>
concept C = true;

static_assert([]<int I>() -> decltype([]<C auto = I>{ return true; })
    { return {}; }.template operator()<{}>()());
```
is accepted in GCC, but Clang crashes:
```
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-19.1.0/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-14.2.0 -fcolor-diagnostics -fno-crash-diagnostics -std=c++20 -Wall -Wextra -pedantic-errors -stdlib=libc++ <source>
1.      <source>:5:45: current parser token ')'
 #0 0x00000000036fdb08 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x36fdb08)
 #1 0x00000000036fbc74 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x36fbc74)
 #2 0x0000000003647be8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007ee200442520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x0000000007281d4d clang::StmtVisitorBase<llvm::make_const_ptr, (anonymous namespace)::IntExprEvaluator, bool>::Visit(clang::Stmt const*) ExprConstant.cpp:0:0
 #5 0x000000000724bbfe Evaluate(clang::APValue&, (anonymous namespace)::EvalInfo&, clang::Expr const*) ExprConstant.cpp:0:0
 #6 0x0000000007262bee EvaluateInPlace(clang::APValue&, (anonymous namespace)::EvalInfo&, (anonymous namespace)::LValue const&, clang::Expr const*, bool) ExprConstant.cpp:0:0
 #7 0x000000000726ada9 clang::Expr::EvaluateAsConstantExpr(clang::Expr::EvalResult&, clang::ASTContext const&, clang::Expr::ConstantExprKind) const (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x726ada9)
 #8 0x000000000621686e clang::ActionResult<clang::Expr*, true> calculateConstraintSatisfaction<calculateConstraintSatisfaction(clang::Sema&, clang::NamedDecl const*, clang::SourceLocation, clang::MultiLevelTemplateArgumentList const&, clang::Expr const*, clang::ConstraintSatisfaction&)::ConstraintEvaluator>(clang::Sema&, clang::Expr const*, clang::ConstraintSatisfaction&, calculateConstraintSatisfaction(clang::Sema&, clang::NamedDecl const*, clang::SourceLocation, clang::MultiLevelTemplateArgumentList const&, clang::Expr const*, clang::ConstraintSatisfaction&)::ConstraintEvaluator const&) SemaConcept.cpp:0:0
 #9 0x000000000621835a CheckConstraintSatisfaction(clang::Sema&, clang::NamedDecl const*, llvm::ArrayRef<clang::Expr const*>, llvm::SmallVectorImpl<clang::Expr*>&, clang::MultiLevelTemplateArgumentList const&, clang::SourceRange, clang::ConstraintSatisfaction&) SemaConcept.cpp:0:0
#10 0x00000000062188a7 clang::Sema::CheckConstraintSatisfaction(clang::NamedDecl const*, llvm::ArrayRef<clang::Expr const*>, llvm::SmallVectorImpl<clang::Expr*>&, clang::MultiLevelTemplateArgumentList const&, clang::SourceRange, clang::ConstraintSatisfaction&) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x62188a7)
#11 0x0000000006219467 clang::Sema::CheckInstantiatedFunctionTemplateConstraints(clang::SourceLocation, clang::FunctionDecl*, llvm::ArrayRef<clang::TemplateArgument>, clang::ConstraintSatisfaction&) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x6219467)
#12 0x0000000006ada2fa clang::Sema::FinishTemplateArgumentDeduction(clang::FunctionTemplateDecl*, llvm::SmallVectorImpl<clang::DeducedTemplateArgument>&, unsigned int, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, llvm::SmallVectorImpl<clang::Sema::OriginalCallArg> const*, bool, llvm::function_ref<bool ()>) (.constprop.0) SemaTemplateDeduction.cpp:0:0
#13 0x0000000006adae4a void llvm::function_ref<void ()>::callback_fn<clang::Sema::DeduceTemplateArguments(clang::FunctionTemplateDecl*, clang::TemplateArgumentListInfo*, llvm::ArrayRef<clang::Expr*>, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, bool, bool, clang::QualType, clang::Expr::Classification, llvm::function_ref<bool (llvm::ArrayRef<clang::QualType>)>)::'lambda1'()>(long) SemaTemplateDeduction.cpp:0:0
#14 0x0000000006097151 clang::Sema::runWithSufficientStackSpace(clang::SourceLocation, llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x6097151)
#15 0x0000000006af201f clang::Sema::DeduceTemplateArguments(clang::FunctionTemplateDecl*, clang::TemplateArgumentListInfo*, llvm::ArrayRef<clang::Expr*>, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, bool, bool, clang::QualType, clang::Expr::Classification, llvm::function_ref<bool (llvm::ArrayRef<clang::QualType>)>) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x6af201f)
#16 0x00000000068f68ef clang::Sema::AddMethodTemplateCandidate(clang::FunctionTemplateDecl*, clang::DeclAccessPair, clang::CXXRecordDecl*, clang::TemplateArgumentListInfo*, clang::QualType, clang::Expr::Classification, llvm::ArrayRef<clang::Expr*>, clang::OverloadCandidateSet&, bool, bool, clang::OverloadCandidateParamOrder) (.constprop.0) SemaOverload.cpp:0:0
#17 0x00000000068f6d23 clang::Sema::AddMethodCandidate(clang::DeclAccessPair, clang::QualType, clang::Expr::Classification, llvm::ArrayRef<clang::Expr*>, clang::OverloadCandidateSet&, bool, clang::OverloadCandidateParamOrder) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x68f6d23)
#18 0x0000000006907473 clang::Sema::BuildCallToObjectOfClassType(clang::Scope*, clang::Expr*, clang::SourceLocation, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x6907473)
#19 0x0000000006512c8f clang::Sema::BuildCallExpr(clang::Scope*, clang::Expr*, clang::SourceLocation, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation, clang::Expr*, bool, bool) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x6512c8f)
#20 0x00000000065186fc clang::Sema::ActOnCallExpr(clang::Scope*, clang::Expr*, clang::SourceLocation, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation, clang::Expr*) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x65186fc)
#21 0x0000000005fa512b clang::Parser::ParsePostfixExpressionSuffix(clang::ActionResult<clang::Expr*, true>) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x5fa512b)
#22 0x0000000005f9ce71 clang::Parser::ParseCastExpression(clang::Parser::CastParseKind, bool, bool&, clang::Parser::TypeCastState, bool, bool*) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x5f9ce71)
#23 0x0000000005fabac9 clang::Parser::ParseConstantExpressionInExprEvalContext(clang::Parser::TypeCastState) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x5fabac9)
#24 0x0000000005f81cbf clang::Parser::ParseStaticAssertDeclaration(clang::SourceLocation&) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x5f81cbf)
#25 0x0000000005f71028 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x5f71028)
#26 0x0000000005f27cfa clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x5f27cfa)
#27 0x0000000005f29ac8 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x5f29ac8)
#28 0x0000000005f1877a clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x5f1877a)
#29 0x0000000003fce825 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x3fce825)
#30 0x0000000004274201 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x4274201)
#31 0x00000000041f699b clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x41f699b)
#32 0x000000000435a843 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x435a843)
#33 0x0000000000c874dc cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0xc874dc)
#34 0x0000000000c8146d ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#35 0x0000000004017309 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
#36 0x0000000003648013 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x3648013)
#37 0x0000000004017529 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
#38 0x0000000003fdd947 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x3fdd947)
#39 0x0000000003fde2fd clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x3fde2fd)
#40 0x0000000003fe7d4c clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0x3fe7d4c)
#41 0x0000000000c847f1 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0xc847f1)
#42 0x0000000000b5c2d4 main (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0xb5c2d4)
#43 0x00007ee200429d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#44 0x00007ee200429e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#45 0x0000000000c80f0e _start (/opt/compiler-explorer/clang-19.1.0/bin/clang+++0xc80f0e)
```
Online demo: https://gcc.godbolt.org/z/74aWojehv

It is a modified example from https://stackoverflow.com/q/77431308/7325599
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzsW99zozjy_2vIi8ouEGDwQx4YJ9lv9jtzyY1TO_vmEpKwtZElVhIZ5_76KwkwBv9IMsdu7dXe1uxMAlL3pz_dajWNQFqztaD02os_efHNFarMRqrrO0rUVS7J6_XThmlQKrlWaOv5mTfz6z_Yg5_sHz8zdFtyZKgXLjBHWoMnL7z1_AxLgWlpwAJ44Q0wqqJeaMd7fqYNMgyvkNZUGQ-mtXIvXDBhwL2dDlMPzsHEC28BoZib15IejlsAVBnpBLvhySegqKmUaPUAL7nx4NzzMwAAOLjvJZ_srXrEtMUOZEkVMlLVir1w0Y5roLR_zxsbWho8P2MaIGwtpQQwAX5aLDy4AHllwIIjsQZYIb2h2guzwcTHz7fZ8hboKt8yAxDIqzVQtJTKACPBxpjSTYJ3HrxbM7Op8imWWw_ecf7S_jMplfyNYuPBO6Z1RbUH7wASFgnmFaHAbGiNAOQIPxuFMLXwSkVLJTHVmhKgZaXqy3Ym0lpihqw5qhJAY8VKM_X8bGkQfgak2pa1Lf7U8-ePdWgApNbVlgpjIQMP3snSYsJyWzJO1YTuSi4VVfaaZWUSzKfB1PfgXc5Ee7EOKTBZk-9IFZMITNZgIq00VJZWZmXKykw1mGyt7WAy2aWzCdLbiX4VBu288IYJQzmYFEJOXqjKpab2PpgswWSyxnhipOR4g5jwwpuLKO3gIJrCqQ8mBZZcqglhaC2kNgzrWoPjtX9ZG-KFN83igD6YfEOcg8k3ujMKgUlJCRKG4QlVSqp6PGe5F95wljezgBcuGo-4dRRYmnvXwiz2wiyyfwFcKUWFASVSmipg5DMVwIOJi9bExr8HQx_4O7_9L5wVJPdT4KIozLww06-6_uFRMWGcm5_qQEm7QQp9X0ltFEVbD85ssDBh7CJ1S-M_8LcHP_m7BlSzZD0YBgPIOU6iU5AXnCJRlQ9iydYCcQ-mlXApjQAurYrxAFoIHUDYBxglOU3BwkbEV4rlC1WvNaL_Q4Jwqydt-OqNWUhh6M5McWkXle_-r-WHjfyEUuj7UQRj6Dem2IiBd7t0tppFE85EtZusRVXfwFMtpzMH2U3pAEeHgBOYBiQioDbTMbk0W_ML08xI9Qlpm847urfoma6wFNqsSqOs8z2YIiHF61ZWGgi0pbp0ETOvJ9wLc7sr1e0L4lWdVxcgl5LX4euFmdPkwXQAADglHswsU1bCwv6OxCmG4r5BUZ4XFDQaaV909vgL4hVtAvcN7FbEvShkM_pAjAX0EYSzPsIZzGmH8F488nqRjQT0jdGfneQW_humNd5628RkYCIiaD6U26G1dme6Fefu9czvj_5KdcVPYM2WT826uWRNkx8OdP0_E8Sa5CaNkxYai7tVlh7yMYPBLJ3RHnZsmBSNZa5i6mGuua-LmFuAEceVrU-cFQrZ7IwM0wVyUuz8N0b0FxjdomOu_oG2lNxQzHvuP5zmNp7PEqNaZO_ml4ob9pm-UP7U1FJZUwl8Zvqif86pO2fJbB_J3Yguv7hC7U1bf1Dv4k1P_F14PlA0B9bORV3ln8gM88FKSMMYgcWG4uexOez2qUwp9PqVFscrq5tgI-VwznKLOP-FYiPV_bbkpxelnTQE82Muqb38FYk1_YBDLnBtiyV_yHWKEjBks1byXgf8fakeZWNonFBvDNZFwcBF82h2yUX39bblnsPuKuHwtbZ36PVg0VzKIK0U69N3enNIduPQP5tIS1VHZK_wtrsvLNBpIu-YYHozNOKGkupEvA9JPknTxQB2gik5SZoLzf2TiXsSuOycYSzrvVUdwMaOgxLwnUg7ih4UWzOB-AJxnqm1KzqOisBDuUUDdKVcsNgBoG2a3DZOnzoRpZKl9Wudu45Qn8hi4dCzNELgRTJyXr-72-l3QzDiPEf4eVWIc2bXrhp6Sr87Ii6sEZuQao-8O2F2qXL8iGg92P57IOCfFeJPrrF2rnbmSGtWsC6dvBkHb5m71-mCpf07c32uhKNtTlDguhf7iErbx_j3RlHvOXfmz5MgDk7nB1WJb8xsllVRMMxo0_pYlkdPZcd59b0BOVoWrO3osmDcXysF9IPitJX_i_W_UKyPFA21v7to6DUaZmkxS-mZaMgI-ULNRu63qQUShJGjjsn7AsJezTCmWj8ipoa1wa-_fqVYKvJDwTSW8z4Yig8vVHGJyJ6WJTVvh9fRrEek0PZBEevTs3tiO-tEEkuGDiUwfMOhZxx50UV_MWY_xOgIy6jmtVtG_ebN3E-i5AzrnyrGiS2anuRD_hvF5qFwVNVk9vYOLO2lYUwfdHveudF8qQzKOf0g60OJY1FXk9NR13_ajwOI0zMZaE_dcfvvL8bVORD9RDAWozVne0ahP2A0nRX4TArA5kH8FzM6HoOWo47B3iN3XKA4gPkhgEf3zuzg50epTcF2FhjVmknhSsPdoEX_gQ7uaLY16DvbYN-2OaZJcNG2BdKmM6xv0uFgO879XnfLh9E-rMwOp9rkZ6cvjduFhlPH83Rjb8dGOPB0jvD8MhsHrwVqRu5F-8KqebdwnqKBneO52MLujIr6RqUBzouLRi3dsYrMnaqw2z5S6ERjdbAkx-vUNBA7A-K-AUngw_SiAWdBtzek2jvnYp45GaUkM0axvDJU_8iIoY4xw9lR0xE36xMHE9xvcR0Rd7szVAnEzxI4BgF2BBNrq2NZUjwuA87GjoFkwMAc4cuh8yRL1x-unzUOTX8o0e8VfTRq2K3D_Cclq9LtZid6zt3--kWSitP7bSlVu-bHXDXOuM70tG96kCbJsfOz5dPZ9yV_SHnSAOlg9gq-sMA0hXG_M0zoT1RkzZvKen-kuDI0a7uv4x3OqNXvwfUPvEQwiaDf2x3vlE0jgpxANyauRnOHq1eRREExm8_zPmm1prr7j-lp3s4bMmJcNug67L2KIwpjlEZhv5xzKDsTXvapMr1k4ohppEHVYe7VBT5Ok4hggHGw2iIr4EwLZ4OO3mH1r8GFa0uPCb3G1iGPBsiDaEZAS_EieHJrO73Y7z8yY_CKwMo4PkcxB0SxF6qOmxL9AzeRHyShPx-zP18rbsJkESzkdosEGa7Okz5z5-7sNVla7Yj3ji8tjWJi3ST62qH7CasV3u2CoP4lR5rhlXbDGwp7g-2FlVGIGd3eHohDnNuwl-rgvh2SDergmnA3Zd_5PtP4_lnmJ5wxG5w_S_0gPPDDqVNm9Z2vlViigvLXHpd_Thu7wdmFeTIMqRj2Cve_XUi4XmGJlKnbhKd9n_b3XkLmUXKWNecrdLTPtVT2kvNgoh1w7uX6haFZrxAZ9bxVY2wXQIMyhFBYkI9S8bPM9Xkefpb50SGDS3l37_cSMVWfaf8IdU1w_IEEWor2BEb9s8EFTUiEz4G9Ofi5t92f2OfPEf8nEjhadelI6SgLBntzlBRNddnWFS1klyyyo9dj53bekSoJi6dD26vb_DzGkETA4hxHXS2wUzc4twznZP7Bc8tuSicwGgqkkQ9WKztnpQ1SZnVgzLtV0OhARTxwqF_4FNTCx_KJFdkoPPgE5EFwJiggdCu9MBt-84HxdC1JLrmZSrX24N2_PHiXROib_I1uXupPae4NYBogsJWEFYwSQHdoW3IKCiW3A4HaIPxsC4KCy-_NtyS_W5FJFAahb-1MQhjH8_kVuQ7JPJyjK3odJGEaRVE8g1eba-JHCM5y7OM49qMwoGkc-xTBZBanOfGjK3YNfRj70A9gEMx8OM1DGpB4nkLixxGioRf5dIsYn9rlYO26ch-uXAcwDuP5FUc55dp9jgShoN-Bu-tB6MU3V-raffOSV2vtRT5n2uhOjGGG0-v7xS2QAtQFFaD79h74zswGtN8k4fbYEiVg_w1Q-wnLVaX49Y9_ftMY8nIN_x0AAP__xTxD6Q">