incorrect error on correct code and crash on bad code in forward declaration of enum in template

[llvmbot]

Bugzilla Link	22943
Version	3.5
OS	Linux
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor

Extended Description

template struct A {
enum E : T;
};
A a;
template enum A::E : T { e1, e2 };
#if _WRONG
A::E er = e1;
#else
A::E e = A::e1;
#endif

Should compile clean but with

clang++ -std=c++11
a.cpp:9:15: error: no member named 'e1' in 'A'; did you mean simply 'e1'?
A::E e = A::e1;
^~~~~~~~~~
e1
a.cpp:5:38: note: 'e1' declared here
template enum A::E : T { e1, e2 };

clang++ -std=c++11 -D_WRONG
clang: error: unable to execute command: Segmentation fault (core dumped)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 3.5.0 (tags/RELEASE_350/final)
Target: powerpc64le-unknown-linux-gnu
Thread model: posix
clang: note: diagnostic msg: PLEASE submit a bug report to http://llvm.org/bugs/ and include the crash backtrace, preprocessed source, and associated run script.
clang: note: diagnostic msg:

---

Testcase (not _WRONG) section is taken directly from the C++2011 standard
14.5.1.4 Enumeration members of class templates

the _WRONG section was an attempt to fix according to the clang diagnostic message.

[Endilll]

Still crashing as of post-17 trunk: https://godbolt.org/z/9qeerY691

clang++: /root/llvm-project/clang/lib/AST/Decl.cpp:2539:
clang::APValue* clang::VarDecl::evaluateValueImpl(llvm::SmallVectorImpl<std::pair<clang::SourceLocation, clang::PartialDiagnostic> >&, bool) const:
Assertion `!Init->isValueDependent()' 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 -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -std=c++11 -D_WRONG <source>
1.	<eof> parser at end of file
2.	<source>:7:11: LLVM IR generation of declaration 'er'
3.	<source>:7:11: Generating code for declaration 'er'
 #0 0x0000000003678548 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3678548)
 #1 0x00000000036763cc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x36763cc)
 #2 0x00000000035c3c28 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007f4fc2c54420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #4 0x00007f4fc271700b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #5 0x00007f4fc26f6859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #6 0x00007f4fc26f6729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #7 0x00007f4fc2707fd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #8 0x0000000006de3353 (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6de3353)
 #9 0x0000000006de33db clang::VarDecl::evaluateValue() const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6de33db)
#10 0x000000000396e1cb clang::CodeGen::ConstantEmitter::tryEmitPrivateForVarInit(clang::VarDecl const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x396e1cb)
#11 0x000000000396e581 clang::CodeGen::ConstantEmitter::tryEmitForInitializer(clang::VarDecl const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x396e581)
#12 0x0000000003a40897 clang::CodeGen::CodeGenModule::EmitGlobalVarDefinition(clang::VarDecl const*, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3a40897)
#13 0x0000000003a62861 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3a62861)
#14 0x0000000003a62eb3 clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3a62eb3)
#15 0x0000000003a6bfeb clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#16 0x00000000048d3636 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#17 0x00000000048c5dd8 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x48c5dd8)
#18 0x0000000005d905f4 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5d905f4)
#19 0x00000000048d06a8 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x48d06a8)
#20 0x0000000004138c59 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4138c59)
#21 0x00000000040bcfee clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x40bcfee)
#22 0x0000000004219096 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4219096)
#23 0x0000000000bcd462 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbcd462)
#24 0x0000000000bc5c4a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#25 0x0000000003f1d239 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
#26 0x00000000035c40d4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x35c40d4)
#27 0x0000000003f1d82f 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
#28 0x0000000003ee5795 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ee5795)
#29 0x0000000003ee61fd 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+++0x3ee61fd)
#30 0x0000000003eedd25 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3eedd25)
#31 0x0000000000bcb717 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbcb717)
#32 0x0000000000ac5481 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xac5481)
#33 0x00007f4fc26f8083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#34 0x0000000000bc572e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbc572e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)

[llvmbot]

@llvm/issue-subscribers-clang-codegen

[shafik]

If we look at this simpler example: https://godbolt.org/z/4sGr3TKPM

struct A {
    enum E :int ;
};

enum A::E :int  { e1, e2 };

A::E er = e1;

clang accepts while gcc/MSVC reject. It looks like we are missing a diagnostic here which would prevent this from going into codegen.

[llvmbot]

@llvm/issue-subscribers-clang-frontend