<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/121009>121009</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            ICE on invalid explicit instantiation as abbreviated function template: non-canonical or dependent type in IR-generation
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            c++20,
            clang:frontend,
            crash-on-invalid
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          hubert-reinterpretcast
      </td>
    </tr>
</table>

<pre>
    The following source attempts to explicitly instantiate something that is not completely-specialized.
Clang ICEs.

With assertions enabled, we see "non-canonical or dependent type in IR-generation".

Online compiler link: https://godbolt.org/z/WvKobK4P7

### SOURCE (`<stdin>`)
```cpp
template <typename T>
void f(auto) {}

template void f<int>(auto);
```

### COMPILER INVOCATION
```
clang++ -std=c++20 -Wall -Wextra -Werror -pedantic-errors -S -o /dev/null -xc++ -
```

### ACTUAL COMPILER OUTPUT (without assertions enabled)
```
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/wandbox/clang-head/bin/clang++ -std=c++20 -Wall -Wextra -Werror -pedantic-errors -S -o /dev/null -xc++ -
1. <stdin>:4:27: current parser token ';'
2.      <stdin>:2:6: instantiating function definition 'f<int, type-parameter-0-0>'
3.      <stdin>:2:6: LLVM IR generation of declaration 'f'
4.      <stdin>:2:6: Generating code for declaration 'f'
 #0 0x000056a045979a98 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/wandbox/clang-head/bin/clang+++0x301da98)
 #1 0x000056a04597788e llvm::sys::RunSignalHandlers() (/opt/wandbox/clang-head/bin/clang+++0x301b88e)
 #2 0x000056a0458f75f9 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007d1275445320 (/lib/x86_64-linux-gnu/libc.so.6+0x45320)
 #4 0x000056a045c33a68 clang::CodeGen::CodeGenFunction::EmitReturnBlock() (/opt/wandbox/clang-head/bin/clang+++0x32d7a68)
 #5 0x000056a045d32f3c clang::CodeGen::isAggregateTypeForABI(clang::QualType) (/opt/wandbox/clang-head/bin/clang+++0x33d6f3c)
 #6 0x000056a045d27c9e (anonymous namespace)::X86_64ABIInfo::getIndirectResult(clang::QualType, unsigned int) const X86.cpp:0:0
 #7 0x000056a045d2533d (anonymous namespace)::X86_64ABIInfo::computeInfo(clang::CodeGen::CGFunctionInfo&) const X86.cpp:0:0
 #8 0x000056a045e7aab1 clang::CodeGen::CodeGenTypes::arrangeLLVMFunctionInfo(clang::CanQual<clang::Type>, clang::CodeGen::FnInfoOpts, llvm::ArrayRef<clang::CanQual<clang::Type>>, clang::FunctionType::ExtInfo, llvm::ArrayRef<clang::FunctionType::ExtParameterInfo>, clang::CodeGen::RequiredArgs) (/opt/wandbox/clang-head/bin/clang+++0x351eab1)
 #9 0x000056a045e7ae8e arrangeLLVMFunctionInfo(clang::CodeGen::CodeGenTypes&, bool, llvm::SmallVectorImpl<clang::CanQual<clang::Type>>&, clang::CanQual<clang::FunctionProtoType>) CGCall.cpp:0:0
#10 0x000056a045e7c3aa clang::CodeGen::CodeGenTypes::arrangeFunctionDeclaration(clang::FunctionDecl const*) (/opt/wandbox/clang-head/bin/clang+++0x35203aa)
#11 0x000056a045c5d188 clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/wandbox/clang-head/bin/clang+++0x3301188)
#12 0x000056a045c565fa clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/wandbox/clang-head/bin/clang+++0x32fa5fa)
#13 0x000056a045c5a48b clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/wandbox/clang-head/bin/clang+++0x32fe48b)
#14 0x000056a045c55600 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (/opt/wandbox/clang-head/bin/clang+++0x32f9600)
#15 0x000056a04601a5fc (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#16 0x000056a046013b7d clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/wandbox/clang-head/bin/clang+++0x36b7b7d)
#17 0x000056a047df028f clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) (/opt/wandbox/clang-head/bin/clang+++0x549428f)
#18 0x000056a047ca8ee0 clang::Sema::ActOnExplicitInstantiation(clang::Scope*, clang::SourceLocation, clang::SourceLocation, clang::Declarator&) (/opt/wandbox/clang-head/bin/clang+++0x534cee0)
#19 0x000056a04767dc34 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/opt/wandbox/clang-head/bin/clang+++0x4d21c34)
#20 0x000056a04767bfb1 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/opt/wandbox/clang-head/bin/clang+++0x4d1ffb1)
#21 0x000056a04770a4ee clang::Parser::ParseDeclarationAfterTemplate(clang::DeclaratorContext, clang::Parser::ParsedTemplateInfo&, clang::ParsingDeclRAIIObject&, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/wandbox/clang-head/bin/clang+++0x4dae4ee)
#22 0x000056a0477092d3 clang::Parser::ParseExplicitInstantiation(clang::DeclaratorContext, clang::SourceLocation, clang::SourceLocation, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/wandbox/clang-head/bin/clang+++0x4dad2d3)
#23 0x000056a0477091d6 clang::Parser::ParseDeclarationStartingWithTemplate(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&) (/opt/wandbox/clang-head/bin/clang+++0x4dad1d6)
#24 0x000056a04767ab95 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/wandbox/clang-head/bin/clang+++0x4d1eb95)
#25 0x000056a04765c84e clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/wandbox/clang-head/bin/clang+++0x4d0084e)
#26 0x000056a04765b876 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/wandbox/clang-head/bin/clang+++0x4cff876)
#27 0x000056a0476580de clang::ParseAST(clang::Sema&, bool, bool) (/opt/wandbox/clang-head/bin/clang+++0x4cfc0de)
#28 0x000056a046287e66 clang::FrontendAction::Execute() (/opt/wandbox/clang-head/bin/clang+++0x392be66)
#29 0x000056a046201234 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/wandbox/clang-head/bin/clang+++0x38a5234)
#30 0x000056a04634ea6e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/wandbox/clang-head/bin/clang+++0x39f2a6e)
#31 0x000056a0438ddca0 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/wandbox/clang-head/bin/clang+++0xf81ca0)
#32 0x000056a0438dac61 ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#33 0x000056a04605a649 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::$_0>(long) Job.cpp:0:0
#34 0x000056a0458f73dc llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/wandbox/clang-head/bin/clang+++0x2f9b3dc)
#35 0x000056a04605a086 clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (/opt/wandbox/clang-head/bin/clang+++0x36fe086)
#36 0x000056a04601eb07 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/wandbox/clang-head/bin/clang+++0x36c2b07)
#37 0x000056a04601ed6e clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/wandbox/clang-head/bin/clang+++0x36c2d6e)
#38 0x000056a04603a6e0 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/wandbox/clang-head/bin/clang+++0x36de6e0)
#39 0x000056a0438da40f clang_main(int, char**, llvm::ToolContext const&) (/opt/wandbox/clang-head/bin/clang+++0xf7e40f)
#40 0x000056a0438e7f37 main (/opt/wandbox/clang-head/bin/clang+++0xf8bf37)
#41 0x00007d127542a1ca (/lib/x86_64-linux-gnu/libc.so.6+0x2a1ca)
#42 0x00007d127542a28b __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2a28b)
#43 0x000056a0438d8a05 _start (/opt/wandbox/clang-head/bin/clang+++0xf7ca05)
clang++: error: clang frontend command failed with exit code 139 (use -v to see invocation)
clang version 20.0.0git (https://github.com/llvm/llvm-project.git b84218526d364cb9fda23bfca164d25a7b03a641)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/wandbox/clang-head/bin
clang++: note: diagnostic msg: Error generating preprocessed source(s) - ignoring input from stdin.
clang++: note: diagnostic msg: Error generating preprocessed source(s) - no preprocessable inputs.
```

### EXPECTED COMPILER OUTPUT
(non-ICE error)

</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzkWltz47aS_jX0C0ouEKB4efADrbFmlTM59tpOJm8uEGhK2KEAHhD0yOfXb4GkzItl-aIku1Un5Ywk4vb1143uJtCsquRaAVx480tv_uWM1XajzcWmzsDYmQGpLJjSgOWssmeZFk8X9xtAuS4K_VOqNap0bTggZi1sS1shqxHsykJyaYsnJFVlmbKSWUCV3oLduDF2wyySFVLaIq63ZQEWiqdZVQKXrJD_BnHu4XRRMLVGq8VV5X55OP0u7QaxqgJjpVYVAsWyAoRHFugnoAoAeYQorWacKa0kZwXSBgkoQQlQFtmnEpBUaHU7W4MCw9w0HiHd9NeqkAoaQLIAgwqpfng0RRtry8qjqUeWHlmutch0Yc-1WXtk-W-PLL8__kNn_whuonYaj9D2D91d_3a7uEIeib0Qe3RRWSGVR6_cL5K4riFu_3hZejh1DBaOKY8uHFbFtoDu3QCcPmopUO6RmNVWeyRBXnTpRV_aJZ8Hdr3oQirrxj139-jlcL0p0sX1rzerb1e3aPXP368X6f3q-p-T7twpwyOXHrlEs8oKj37h7U-C0ew7Kwo0-w47a5j7NEYbNCtBON3zWfO7QrM7NNPII0sBjx5ZqtoN2vH9rMcApov739JvPc7r3-5vfrt31P6UdqNre9AuksmUN9-u0rsrVNXZVlrEUFavkYFSG-vMdqJnaTd1ds711iPLonjcf8xKo_8HuPXIUlZVDZVHlogpgaTiRS0A2Q0gbli1QRnjP6xhHJyFlgZKozlUFYhu07jHbiSrKs3dFhHI1ApV3MjSOqO8s4z_QKLelg4WTvE5ujF6bdgWMbOut6CsA-wo1aVD9JMpkemdR5aNvmYbYMIjy0yq_aO_XIX-ORqaOk0Dj6YkcjB5bYzbhyUzFRhk9Q9QyHNtl-5fnJJz1Pw3noB4NA3d-N6ZOCeS14o7fSMBuVSy-eqRaG_9ZNHs91nJDNuCBTPDM9zsCbcSPb7St2-__4pWt6h3E0jnSAAvWPezWamZKjg-1dduCrVGXAvnOc0rEyGPUIzwDmOM5yHDwTyJEpbEqLE-mno0rZ6q9suNkco25nHfGljcdzLs54OurAG29UjoiGj4SBpH9FFL8cgl3lHsC5bE7YZyMP0JzCiO4RDM21rdybVixX8xJQowVQPhNCRZHEOPhIyQxHk0zxO0cNvvFrh-BPM0AuCRuCNj1GehlYWdPXd-mKa4-b-dn3bzR8In0TwI5pTgDn4hM48sd3H4EAazQqp6N1urum3g55U-DxvIzZAecDACzCllYYxaMRvKFlrAV1CjH8vO1NuHV1tpb8HWRl0Wmv84mVIiIhYOlDsfIRSU5JS_ilBW6XptYM0s3D-VsNQmvVx5JB70_--aFa7tNJRUhDnlPcpwjJJEPHHxP3ah_2mr6wq58FmVze5IWiR_NLpKL1crlev20RrsSglpgNtbqOrCvoZ9gWrVpEpiv524VpVFf8ThAbOJJujmlIpPoHO5SG2heTDCNbaSr3sDaTuGb6GLR-ggYizz37JBx0K3q5kxTK3BOcnxwiOETDnyPLoYPGyodD548epyy2au69JWrlfvU1Jj2NMt5OMJj67yYqE92rZDs5d2toX-9lIHB9_so0urs6OS3cK_amlApGZdnbYX5j6wzO_3QjLVJ8SA3qelVzXdRo5M62JMzt2WFcXvwK02q21ZfFAd4ZSgQwP2cG-MtvrZZBK0-LpgRTGxZxeN8ER-Thn7uD3vl_3SR-cxWcMO7f7ySHqiJgmmjHWZKqH-OLDyufDjN6PDr1rUBfSx4WuhM1b0YPfZ0ViYtpcTZazf9vnvrKjhZOko9v047qUjE-nCef6mng5L938pFcnZPB_ojE6kYkGcfU6q12U5DS8EcdbjnWQg83mI8Ufx3uvyGzxCh26Iun1yMsVJiHEPeZSShNhn85y_FU475C753rsq97hNBI_j_2p0XboAQBLUSn5Zy0KAOeB7wgk0mkViyOYl4z9AiYVWVb0F8zkQn2cyzKIsEj2To8QkEjkmcT6Eewdb1n5b9Uc3b_mSu-Z19pvmndM8GHSfDaOPKuPPE8ScB0lA4rwXc5ThRJzFAPiwmCm31-qqO7HqZX4pI9cldPjfK_rRxn2Y0abL2D4vPQ04wGC7jPKBKIwEp8Fw6ZvmBXzwfRDy0tyC6bGlSqTWGpnV1iUFUyMdCLA4uoK4786oXA6yD57HRi21uXVReaXkyWE2EMTnNHgmiOAJQVk-ToAPEtRsyDEFrk2qtWu9K4G_lKjnqHvFPCTxiOGPMfmy_9Tmpgb713Hs5_k-KXUcj1KZKMIsAPiQEe7lfM3qjjD6Ab4GKrxNV6vrrD3ce4vWg2o6qsiUc6gqZyYyl2BOJJtBANCTTSZkJ0TQo6y8w-O9xfTnXd__OzIFEbQnk07J9EX4Xsu9s8xYqdbfpd18zoA_Rc6J4vsi7MUPJs6RZcn8veL_DaJ-sMcBf3ial4MsmfdkzcdkzXkcHPdyVzsLRrV5_UHS_gyhX8SlU6XGOA4G7iacSJ3F0fEd8nqqe12yf9VwY834DGCUAR86OegzuDZDX21LbeydbfbbiTuC53kcDXZENBE3xuKlktO7-0nG6BCOj1FOTnQDnnMsBpoYJbohiSMIR5pYGrfzlEiHB8g74HXjlk57t0hIBuGApmSMBftknHYuupvVNuZwGKHpAI4PXMbgT1QrjdmcDLLA8WVLSANg4UitHbIe9uOzF4mPiXXq22-SExb2Oh7fttBYCM4w4tx_2DI3QXz45HLDTH9I1Z1Mjp6RRXNffCrcPPY5618-xjcyNBaMhz7aU7nw75stEB89UHwBPRyf5rg5uogyeJVIkDDy8dBLOqXjl_Q5C4OkvSzvJ93fJz6Yhr-mtd0i7Y2eR1POiiJj_MdDrsbeql24M4eFv9DbLVNiutsO6qm5iHXPdOlWb85CB-RYI9W684GtEp8HPDzw3c732x8ZqyR_qJruHYWjzu7BgzVM2mrfPJmOFYUzb20G7a7L4I09fb5YaId4JHho71TjQjujSNAvOjvAfzC9paOCD6g_dBfXttzW6o7lUDyN6DuuqlOMmeRJRgXvrXk-tRwcj_zrf5zmTzmLygHHfbyg06MzyHD0KreNk2Uvgtie8JFHngx0HV47cjjSNR0F7z9BfE4yHPXiR1PxxTj8vEf8X3RWvS77Lzr7Jis7kv2Y4322iJJJ09dRvJeu4R3Pn0iaGMbCcb6DKQvHB3tDgF8G30ex_EAQf43sv5G0k455BYSDE8DxjaALwgHujnn3ScMeZuMu0m6zvx1iP58mRBDg_oQ2wGOEEOU0Qg7bKZlIltN-gwX-uHaDMJ-zj9VuNEP6Ccl0QhJn6OHBjXmo3Iv_w0CAdy9BBpczAZ0oLmZ4jtrJT-GeM9y9tA7baIqauq6mOMs9R3mXcSPe2WnOZAEC_ZR2g2AnbVvE5NPGEuoK0OwRWd0UX8pBfvy8EnoEU0mtEMHn-ByvZSPGx0rtzt2oLA6IH89JKGgY8CzJBSM0yznzw0CQOYsy5wyC7gDynpk1uBwCdQqo1Q-lf6qBInB6vzHABNpqAYXrWupK7jzc3nwUBYgv0ry3vO4FsUpb94KDhGRrpSsrOdpWziGgq6a0bt3XhR0sDYybGoEZkmulXWhHUpW1dQraoqbO7PyvW1PpQTvLCmgXb-twXyvRvPrj5mpxf_VlWqTZdIqVVrPV4qqzt0ZHZ-KCioQm7Awu_IgGSRLEYXS2uSCM8cBPWAL5XGS-wHw-x36WBzHOBMXhmbwgmAQ-IZRQ7OPoXAQxjiFmIQmiJOGRF2DYMlmcOzM612Z91tRqXvjExzg5K1gGRdWUPBPyXAPpEeKRhXvSue79ZugbXJ4602om1SMrZNMw_3JmLhprzep15QW4kJWt-oWttAVcONG1Qt245wrpYUmjVohViGWZgce2GPS5wnFf39vq-GP1zWe1KS4-X9raMfZ4Qf43AAD__yclC2Q">