<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/138098>138098</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Clang ICE on assertion "isa<To>(Val) && "cast<Ty>() argument of incompatible type" with templates using -std=c++23
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          mariete1223
      </td>
    </tr>
</table>

<pre>
    ## Summary 

**Using -std=c++23 Flag**

When referencing a dependent static member function inside a templated class without proper qualification or parentheses (e.g., type_c<T> instead of type_c<T>() or this->type_c<T>()), Clang 21 crashes with an internal compiler error (SIGSEGV) during instantiation.
Instead of a diagnostic message about the misuse, the compiler hits a segmentation fault in Sema::ResolveSingleFunctionTemplateSpecialization.

## Assertion

```
clang-21: /root/llvm-project/llvm/include/llvm/Support/Casting.h:578: decltype(auto) llvm::cast(From*) [with To = clang::FunctionTemplateDecl; From = clang::NamedDecl]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
```

## Stack dump

```
Stack dump:
0. Program arguments: /root/llvm-project/build-assert/bin/clang-21 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -dumpdir a- -disable-free -clear-ast-before-backend -main-file-name prueba.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/root/llvm-project/build-assert -fcoverage-compilation-dir=/root/llvm-project/build-assert -resource-dir /root/llvm-project/build-assert/lib/clang/21 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/9/../../../../include/x86_64-linux-gnu/c++/9 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/backward -internal-isystem /root/llvm-project/build-assert/lib/clang/21/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/9/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -std=c++23 -fdeprecated-macro -ferror-limit 19 -fgnuc-version=4.2.1 -fno-implicit-modules -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/prueba-d0d770.o -x c++ prueba.cpp
1.      <eof> parser at end of file
2.      prueba.cpp:3:10: instantiating function definition 'Derived<int>::f'
 #0 0x0000557ed42a527e llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /root/llvm-project/llvm/lib/Support/Unix/Signals.inc:804:22
 #1 0x0000557ed42a5694 PrintStackTraceSignalHandler(void*) /root/llvm-project/llvm/lib/Support/Unix/Signals.inc:880:1
 #2 0x0000557ed42a2bf2 llvm::sys::RunSignalHandlers() /root/llvm-project/llvm/lib/Support/Signals.cpp:105:20
 #3 0x0000557ed42a4b0a SignalHandler(int, siginfo_t*, void*) /root/llvm-project/llvm/lib/Support/Unix/Signals.inc:418:13
 #4 0x00007f4a3b959420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #5 0x00007f4a3b42600b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #6 0x00007f4a3b405859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #7 0x00007f4a3b405729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #8 0x00007f4a3b416fd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #9 0x0000557ed789d5e9 decltype(auto) llvm::cast<clang::FunctionTemplateDecl, clang::NamedDecl>(clang::NamedDecl*) /root/llvm-project/llvm/include/llvm/Support/Casting.h:578:3
#10 0x0000557ed822727a clang::Sema::ResolveSingleFunctionTemplateSpecialization(clang::OverloadExpr*, bool, clang::DeclAccessPair*, clang::TemplateSpecCandidateSet*) /root/llvm-project/clang/lib/Sema/SemaOverload.cpp:13519:35
#11 0x0000557ed82276cc clang::Sema::ResolveAndFixSingleFunctionTemplateSpecialization(clang::ActionResult<clang::Expr*, true>&, bool, bool, clang::SourceRange, clang::QualType, unsigned int) /root/llvm-project/clang/lib/Sema/SemaOverload.cpp:13575:70
#12 0x0000557ed7c68d31 clang::Sema::CheckPlaceholderExpr(clang::Expr*) /root/llvm-project/clang/lib/Sema/SemaExpr.cpp:21036:58
#13 0x0000557ed7c4ee39 clang::Sema::BuildBinOp(clang::Scope*, clang::SourceLocation, clang::BinaryOperatorKind, clang::Expr*, clang::Expr*) /root/llvm-project/clang/lib/Sema/SemaExpr.cpp:15453:58
#14 0x0000557ed8590b01 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::RebuildBinaryOperator(clang::SourceLocation, clang::BinaryOperatorKind, clang::Expr*, clang::Expr*) /root/llvm-project/clang/lib/Sema/TreeTransform.h:2981:3
#15 0x0000557ed856fe3f clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformBinaryOperator(clang::BinaryOperator*) /root/llvm-project/clang/lib/Sema/TreeTransform.h:13406:65
#16 0x0000557ed8558308 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) /root/llvm-project/build-assert/tools/clang/include/clang/AST/StmtNodes.inc:798:1
#17 0x0000557ed859bb32 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCondition(clang::SourceLocation, clang::VarDecl*, clang::Expr*, clang::Sema::ConditionKind) /root/llvm-project/clang/lib/Sema/TreeTransform.h:4548:16
#18 0x0000557ed85864b3 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformIfStmt(clang::IfStmt*) /root/llvm-project/clang/lib/Sema/TreeTransform.h:8237:5
#19 0x0000557ed855d608 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformStmt(clang::Stmt*, clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::StmtDiscardKind) /root/llvm-project/build-assert/tools/clang/include/clang/AST/StmtNodes.inc:1604:1
#20 0x0000557ed858c522 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) /root/llvm-project/clang/lib/Sema/TreeTransform.h:8052:16
#21 0x0000557ed85883cf clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*) /root/llvm-project/clang/lib/Sema/TreeTransform.h:8035:1
#22 0x0000557ed855d760 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformStmt(clang::Stmt*, clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::StmtDiscardKind) /root/llvm-project/build-assert/tools/clang/include/clang/AST/StmtNodes.inc:1652:1
#23 0x0000557ed85516c4 clang::Sema::SubstStmt(clang::Stmt*, clang::MultiLevelTemplateArgumentList const&) /root/llvm-project/clang/lib/Sema/SemaTemplateInstantiate.cpp:4493:38
#24 0x0000557ed864d097 clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) /root/llvm-project/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp:5345:45
#25 0x0000557ed8651d0c clang::Sema::PerformPendingInstantiations(bool) /root/llvm-project/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp:6585:32
#26 0x0000557ed7810ca9 clang::Sema::ActOnEndOfTranslationUnitFragment(clang::Sema::TUFragmentKind) /root/llvm-project/clang/lib/Sema/Sema.cpp:1151:66
#27 0x0000557ed7811091 clang::Sema::ActOnEndOfTranslationUnit() /root/llvm-project/clang/lib/Sema/Sema.cpp:1191:9
#28 0x0000557ed763a533 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) /root/llvm-project/clang/lib/Parse/Parser.cpp:727:12
#29 0x0000557ed7635704 clang::ParseAST(clang::Sema&, bool, bool) /root/llvm-project/clang/lib/Parse/ParseAST.cpp:171:37
#30 0x0000557ed5564366 clang::ASTFrontendAction::ExecuteAction() /root/llvm-project/clang/lib/Frontend/FrontendAction.cpp:1186:11
#31 0x0000557ed5221958 clang::CodeGenAction::ExecuteAction() /root/llvm-project/clang/lib/CodeGen/CodeGenAction.cpp:1102:5
#32 0x0000557ed5563c21 clang::FrontendAction::Execute() /root/llvm-project/clang/lib/Frontend/FrontendAction.cpp:1076:38
#33 0x0000557ed5474e8b clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) /root/llvm-project/clang/lib/Frontend/CompilerInstance.cpp:1056:42
#34 0x0000557ed572f57d clang::ExecuteCompilerInvocation(clang::CompilerInstance*) /root/llvm-project/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp:265:38
#35 0x0000557ecf7e38c4 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) /root/llvm-project/clang/tools/driver/cc1_main.cpp:290:40
#36 0x0000557ecf7d440b ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) /root/llvm-project/clang/tools/driver/driver.cpp:218:20
#37 0x0000557ecf7d4950 clang_main(int, char**, llvm::ToolContext const&) /root/llvm-project/clang/tools/driver/driver.cpp:259:26
#38 0x0000557ecf810950 main /root/llvm-project/build-assert/tools/clang/tools/driver/clang-driver.cpp:17:20
```

## Program

```
template<typename T>
struct Derived {
    void f(int index) {
        if (index != type_c<T>) {}
    }
    static auto& type_c() {
 }
};

int main() {
    Derived<int> d;
    d.f(0);
}
```

## To quickly reproduce

It happens only with -std=c++23 so it can be reproduced until clang-17.

https://gcc.godbolt.org/z/cETh6s8x7

</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzsWs1y27qSfhp6g6KKBPinhReyFOW65pybTOyTu3RBQFPCDQnwAKBj36efAkhKJK0ktsdOzWJcKosigMbXH7objR9qjNhLgMsgvQrSzQVt7UHpy5pqARZijMnFTvHHywCTABN009Y11Y8oiFbug93nLyPkHoXG8oBsWICvAnyFCdpWdN9V6Cr_6wASaShBg2SuBUUcGpAcpEXGUisYqqHegUZlK5kVSiIhjeCAKLJQNxW1wBGrqDHou7AH1VrUaNWARn-3tBKlYNS3Uho1VIO0BzBgUIALWOwXAV4j-9jAHQvI-jYgH5x0C5QjVU4LAlwEeOnE2IMwYUA-nCn2nzVaV1TuEY4R09QcoEOGqINuQUtaIabqRlSgEWittENzc_3x5sPHr64P3mpHhUNCpRUe_yKIVtcnaBRxQfdSmY4gY-geEN057e0BUC1Ma8Ard4BTZwdhDaLIwL4GaTteStpWFgmJbqCmAVkFZPUFjKru4UbIfQXbnvbbnuybBpiglfjPEZYfc28IK2NAu9f92yzqP9GKOUpCHAdkhQK81UrZAG-r6r4OG63-DWz4GeCtkKxqOZxe3LRNo7SrsabGCrlfHAKySvPCSePAKjcUAS5oa5Uj0DfzqjBqbICLrVa1N7slCtIrPxq3CgVkgzyuru5c0w2wKiBXyDWe1_0nrYH7CunGgThqjoIsEoY6q1CdWXylle8XZwHOUICxx0TWt48nq6J637ohcUMrpBsvasWuAtQpFgcYBzhHJRUV8MWM2hP_N5ayb4i3dfN0AEZlxJVFC_RZq72m9bF389PB2bWi4iH1irqfQgZ4OwwrChmLUWi1aCpAD0V2lyVhK79J9V2GlZDtQ7iXLQqhFjZUu3-j0CHhQiMaopALQ3cVhKUGQCGrgOqQGhvuoFQawh1l30ByFNZUyLAUFYSS1oAa3cKOLljToLDWUKnO1cNacahQIxgKG8HCCu6hQrj7IUzYCEBhXWpaQ9go75IB2dCqQmFZU3sIQWupUFiWTciUtJoyG5CNkigspQq1aiUXch-6uiismZLG6pZZpUNaCeqiS1i28ruQPLROLxOQDUahpXoPNmRN6wgKswSFtpXgX-xBgnaAOeza_R60KxLO2jZ7vkNh6d-HnSd3WnLhYD9ruFBYMnUPmu7h9SI0GNVqBq7Vs62kErvBSgK8dXYyhMBQmEdjoXaiWqOPdfeMBXjbW9DRcgK8XQZ4u1g8_XeKFv004-q-az9nGv2urkf9OLIp-_adan6-y1cN0Km3n-qhmItqz6r6OpXPVH3aGTy4B_a00x-P1c9bv7yLpymO89VGA3OJSVhTpl0o8dN8WIlaWBQvUVjuZcvCe9DGzZZkkyzwIu7ii6ibSjBhXRhrKx9MzDfRhIrrkB2AfQuFDPd16Zz64SGEBwaN82ZXcfKDqUrp8JQnuHeUc23EHoWbu7uP6_XdP1ZfP9xt_rX6ssV36-313ermz4BsYhQqp6mtmwBvuzAb8ojnebRQKHxAvbajCBxEq3iB_F9A1qBKl0s1VBvQiFrkwrcqkYvdQbTCfc1Rc7IiAVnFkZuCRomP3J_yPg6lkKKbZHG-AS3ugQdkLaR1M6mfl8sA50HkZjESoeghiqIoTXPgCaYpzmGUGZhH0z181kJaPzveaspcGnGqpOn3O2WsBlr7-XvtMrhuNv95CtNZ_Slv-UuKB_dC7CWtzEJIFpBVESUBWWHcA47ngLNlgmboOgH_oJJXoANc3CvBh8TmTSAVbgTiHhGeIcK7Ep-j8EsrJ8BMn9a8FNKApTOIOEodPVEPhszAJLuIojkffnjWyIi9kKW6s56bNXprmpLYpZ4x6aElPbS8TCjZLdNlgiN0d6fBWKXhTlvkCellnwltldg19qCB8oVRiyjAV9FDnCQ4cguKro900keCsyjaIU2FgWcIZ05s5sUmJIp2J7HZVGyUFunSLSSehXkkFuMiXZ7E5nOxuaf-RQJzPBJYTAXGWcmzlwkkpOTZSeBybE55seQpLJ-xliDrX60Y8Pr8QsEn-2dLnmeYL1oVkW5REE-CYOE4zekY3qsWfVM9Pt2DrhTlHx4a3bvbTqk5D07RFWNgzGcqhnqj8nFPayq54O4H2F-RM2Quvds6dbqvAdYQTEgaLx0xac9MPGcmY-ynzKwk34qHl_Oz8jW_gGmrmfmMGLO6BW8h2Zi_Mzze-Bz8C5V7mJX8d0urW2-7a9RKv4HDfzldvYC-3EXjPOrpm0wNOcsKTuLz9K1dzvK5ogwOquKgO62Lczy8Bqhr3IPEcUQy5wJFD5JMQSYAZHke5JXLiq-E_NRMod0w5RidW2s3Cn_0C85Z4ZWQVD9-akBTq_R_CclnFUbj_g4sxGmSkjELycTS02W0iyZDdasBbjWVplS6DsjaBT-p5GOtWoPcQts0Pi9aTj31-pilKX3Mv77ArmdyRMGM0v9L3E109_ETL4t4FEDTKXlZCaR8L_KOcn5G37zsTZSOSRI5z8mG6JhN1U4LEhXvrvbrIsNsQWuVqsxI89HauX-zurl1XNja_lNxGFK6fFn0ma_TP5_5zG5H8Lvrv1aSi6cTyE8d5ivVxxziGY4yCstDZ52T_e9tKEkTz2DWU1hMKSyyZEfencLr0o3rlL_h3Zt4SoFJ7oJrr-Ry5ic8-w1-8lTFo4Lr9-rc9bARhlHNf2kwb-SRcebXx71L4mhmTyzFv8Ml60a1kj-lfFoySnvfwMaiFI88CcczzQvC3n8OeoHmb6ExSUdDjedelWfR_3vVW3lVZ1w91WRGdZyx5PyEcdPujH0uSX-2lRV_wD1Ug_6r_pDpD2Es8mcmfrHzmmT3KaXQ575JsnSpL-lTXzxNfbOER8v8vHYjWcPibnPcb3zBfHxqfJyU56u514WJHyju-umVT0mS-nm4V36aumZpzKMfrHA_g3bG_Bn8wdb1-NzZBLh4L8BZWjjABPeAs-mWTBwx-oPl2orZT_KD5J9K74ndcdZfUtitpv5sezZix4a3fw01Xpf2uK9hnRWnbqGQDVE6n6GPo-UPVsQ_RP-rbdNfQ1o6SMse0SQDyzNCUzLJwD777fnR861qvM92xjvZ5Gno3y18tnq6g-EqftSqbb5Aedq-OKv0n_4047pulLY3llp4mft7fMP3sNTNscvF4sF-ljN90zxKnujro-IT4zi37_I6bKub22E0cr-QzDt00_OINM0SkmVjdKub261W0oLk3ZbRkMcDay30r15kIIO40WMn5mguRea_eoSTPCPFOF6mk2R2rTh8BPlG6Hppp6cZtgif8uzpSUSaZoThiXP9hLk35izKs9EMMz2VSJM8gWKHZsmSqEB3EZDBedp-rMmLnGQEft7v6UzFwU96lyGTCTLNcZnmfLqK9EBP0u6P0948JZxo-aK0cIB9691u-8M-h22-LB2PwHiaY2UOpHAZDIvvairk5DRvpTV99JFqzQ5UD1nIykeuNZq-e-ap0aDJkI5xLe5Bu4IewQB6GTne--1Tkk1B8ySJdmhQfB13TIyg39S0qr4Cs0pf1011VgMfwk5NnIy1I_bhhfnWE1W6h-MmazGcyjlF8rkiy7RP1Qf--yM5h7e_-fdbYKZLbyo9zGICs4gjB9MBfHW-_XTA_VWoCYg4P1J19r5WfwHr6WWt4WZjQNb2sQF_28nfMoxW3V0j1B9_oyC_CqIVQshbKyo7wpGQHB48jcdy9ydK5CtweEABjgOymV9y7Frkm77R6am_jNkdi2VDsz62dp10ld1_ctXp5KD0ZjAFMz-9R7xr48r4wmnhjz47OZ3YswzeKvR3K9i36hFpaLTiLYOuwrVFB9o0IA1SsnrsrmA-uaxhFBIWMSrRDk4SOGqlFVVnx2Gc97ccD9Y2_sQbb7srLYu94jtV2YXSziT-46zgw-0hM8WDm_Uv-CXhS7KkF3AZ50kWFXke5ReHyzQqaIF3mFG8pCxOooizNOE4yuOiSJbRhbjEEU6jNIqjAsdJvsBRmuME05ixBGBJgySCmopq4YzWdX8hjGnhMiZFtCwuKrqDyvjruxj3FouDdHOhL72V79q9CZKoEsaakwgrbAWX3eXV6_UHpCSip3uNGL_5vUbcjcpg7Qa1Z28NX7S6upyRL-yh3S2Yqkcn91P_9YQ4D-05ub_E_xMAAP__wHgK6w">