crash on invalid after "error: 'foo' cannot be defined in a type alias template"

[wheatman]

The following invalid code crashes on the current post 17 trunk(2e19760)
https://godbolt.org/z/e7GqqKEKf

template <class T> using foo = struct foo {
  T size = 0;
};
foo a;

It triggers the following assert

clang++: /root/build/tools/clang/include/clang/AST/TypeNodes.inc:74: 
clang::TypeInfo clang::ASTContext::getTypeInfoImpl(const clang::Type*) const: 
Assertion `!T->isDependentType() && "should not see dependent types here"' failed.

The full dump is

<source>:1:39: error: 'foo' cannot be defined in a type alias template
    1 | template <class T> using foo = struct foo {
      |                                       ^
clang++: /root/build/tools/clang/include/clang/AST/TypeNodes.inc:74: clang::TypeInfo clang::ASTContext::getTypeInfoImpl(const clang::Type*) const: Assertion `!T->isDependentType() && "should not see dependent types here"' 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++14 -pedantic-errors <source>
1.	<source>:4:6: current parser token ';'
 #0 0x000000000379d408 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x379d408)
 #1 0x000000000379b0ec llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x379b0ec)
 #2 0x00000000036e3bd8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007f0798c42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007f0798c969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007f0798c42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007f0798c287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007f0798c2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007f0798c39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x0000000006e9af1c clang::ASTContext::getTypeInfoImpl(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e9af1c)
#10 0x0000000006e82df7 clang::ASTContext::getTypeInfo(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e82df7)
#11 0x0000000006e9b09b clang::ASTContext::getTypeInfoInChars(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e9b09b)
#12 0x0000000006e9b1b3 clang::ASTContext::getTypeInfoInChars(clang::QualType) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e9b1b3)
#13 0x0000000007340f25 (anonymous namespace)::ItaniumRecordLayoutBuilder::LayoutField(clang::FieldDecl const*, bool) RecordLayoutBuilder.cpp:0:0
#14 0x00000000073427af (anonymous namespace)::ItaniumRecordLayoutBuilder::LayoutFields(clang::RecordDecl const*) RecordLayoutBuilder.cpp:0:0
#15 0x000000000733e076 clang::ASTContext::getASTRecordLayout(clang::RecordDecl const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x733e076)
#16 0x0000000006e9ac51 clang::ASTContext::getTypeInfoImpl(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e9ac51)
#17 0x0000000006e82df7 clang::ASTContext::getTypeInfo(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e82df7)
#18 0x0000000006e99db7 clang::ASTContext::getTypeAlignInChars(clang::QualType) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e99db7)
#19 0x000000000613ca20 clang::Sema::CheckArgAlignment(clang::SourceLocation, clang::NamedDecl*, llvm::StringRef, clang::QualType, clang::QualType) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x613ca20)
#20 0x000000000616e327 clang::Sema::CheckConstructorCall(clang::FunctionDecl*, clang::QualType, llvm::ArrayRef<clang::Expr const*>, clang::FunctionProtoType const*, clang::SourceLocation) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x616e327)
#21 0x000000000635cebc clang::Sema::CompleteConstructorCall(clang::CXXConstructorDecl*, clang::QualType, llvm::MutableArrayRef<clang::Expr*>, clang::SourceLocation, llvm::SmallVectorImpl<clang::Expr*>&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x635cebc)
#22 0x00000000066a6050 PerformConstructorInitialization(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRef<clang::Expr*>, clang::InitializationSequence::Step const&, bool&, bool, bool, clang::SourceLocation, clang::SourceLocation) SemaInit.cpp:0:0
#23 0x00000000066b93f2 clang::InitializationSequence::Perform(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRef<clang::Expr*>, clang::QualType*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b93f2)
#24 0x00000000062b5114 clang::Sema::ActOnUninitializedDecl(clang::Decl*) (.part.0) SemaDecl.cpp:0:0
#25 0x0000000005f872d6 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f872d6)
#26 0x0000000005f96170 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f96170)
#27 0x0000000005f5f42b clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f5f42b)
#28 0x0000000005f5fbb1 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f5fbb1)
#29 0x0000000005f66e66 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f66e66)
#30 0x0000000005f67d0d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f67d0d)
#31 0x0000000005f5acfa clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f5acfa)
#32 0x000000000401e378 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x401e378)
#33 0x000000000428a9b9 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x428a9b9)
#34 0x0000000004208c9e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4208c9e)
#35 0x000000000436974e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x436974e)
#36 0x0000000000c01496 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc01496)
#37 0x0000000000bf8d2a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#38 0x000000000405f3a9 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
#39 0x00000000036e4084 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x36e4084)
#40 0x000000000405f99f 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
#41 0x0000000004027c05 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4027c05)
#42 0x000000000402866d 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+++0x402866d)
#43 0x0000000004030585 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4030585)
#44 0x0000000000bfe90c clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbfe90c)
#45 0x0000000000af7a71 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xaf7a71)
#46 0x00007f0798c29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#47 0x00007f0798c29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#48 0x0000000000bf880e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbf880e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (wheatman)

The following invalid code crashes on the current post 17 trunk(2e19760) https://godbolt.org/z/e7GqqKEKf

template <class T> using foo = struct foo {
  T size = 0;
};
foo a;

It triggers the following assert

clang++: /root/build/tools/clang/include/clang/AST/TypeNodes.inc:74: 
clang::TypeInfo clang::ASTContext::getTypeInfoImpl(const clang::Type*) const: 
Assertion `!T->isDependentType() && "should not see dependent types here"' failed.

The full dump is

<source>:1:39: error: 'foo' cannot be defined in a type alias template
    1 | template <class T> using foo = struct foo {
      |                                       ^
clang++: /root/build/tools/clang/include/clang/AST/TypeNodes.inc:74: clang::TypeInfo clang::ASTContext::getTypeInfoImpl(const clang::Type*) const: Assertion `!T->isDependentType() && "should not see dependent types here"' 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++14 -pedantic-errors <source>
1.	<source>:4:6: current parser token ';'
 #<!-- -->0 0x000000000379d408 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x379d408)
 #<!-- -->1 0x000000000379b0ec llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x379b0ec)
 #<!-- -->2 0x00000000036e3bd8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #<!-- -->3 0x00007f0798c42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #<!-- -->4 0x00007f0798c969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #<!-- -->5 0x00007f0798c42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #<!-- -->6 0x00007f0798c287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #<!-- -->7 0x00007f0798c2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #<!-- -->8 0x00007f0798c39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #<!-- -->9 0x0000000006e9af1c clang::ASTContext::getTypeInfoImpl(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e9af1c)
#<!-- -->10 0x0000000006e82df7 clang::ASTContext::getTypeInfo(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e82df7)
#<!-- -->11 0x0000000006e9b09b clang::ASTContext::getTypeInfoInChars(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e9b09b)
#<!-- -->12 0x0000000006e9b1b3 clang::ASTContext::getTypeInfoInChars(clang::QualType) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e9b1b3)
#<!-- -->13 0x0000000007340f25 (anonymous namespace)::ItaniumRecordLayoutBuilder::LayoutField(clang::FieldDecl const*, bool) RecordLayoutBuilder.cpp:0:0
#<!-- -->14 0x00000000073427af (anonymous namespace)::ItaniumRecordLayoutBuilder::LayoutFields(clang::RecordDecl const*) RecordLayoutBuilder.cpp:0:0
#<!-- -->15 0x000000000733e076 clang::ASTContext::getASTRecordLayout(clang::RecordDecl const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x733e076)
#<!-- -->16 0x0000000006e9ac51 clang::ASTContext::getTypeInfoImpl(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e9ac51)
#<!-- -->17 0x0000000006e82df7 clang::ASTContext::getTypeInfo(clang::Type const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e82df7)
#<!-- -->18 0x0000000006e99db7 clang::ASTContext::getTypeAlignInChars(clang::QualType) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6e99db7)
#<!-- -->19 0x000000000613ca20 clang::Sema::CheckArgAlignment(clang::SourceLocation, clang::NamedDecl*, llvm::StringRef, clang::QualType, clang::QualType) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x613ca20)
#<!-- -->20 0x000000000616e327 clang::Sema::CheckConstructorCall(clang::FunctionDecl*, clang::QualType, llvm::ArrayRef&lt;clang::Expr const*&gt;, clang::FunctionProtoType const*, clang::SourceLocation) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x616e327)
#<!-- -->21 0x000000000635cebc clang::Sema::CompleteConstructorCall(clang::CXXConstructorDecl*, clang::QualType, llvm::MutableArrayRef&lt;clang::Expr*&gt;, clang::SourceLocation, llvm::SmallVectorImpl&lt;clang::Expr*&gt;&amp;, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x635cebc)
#<!-- -->22 0x00000000066a6050 PerformConstructorInitialization(clang::Sema&amp;, clang::InitializedEntity const&amp;, clang::InitializationKind const&amp;, llvm::MutableArrayRef&lt;clang::Expr*&gt;, clang::InitializationSequence::Step const&amp;, bool&amp;, bool, bool, clang::SourceLocation, clang::SourceLocation) SemaInit.cpp:0:0
#<!-- -->23 0x00000000066b93f2 clang::InitializationSequence::Perform(clang::Sema&amp;, clang::InitializedEntity const&amp;, clang::InitializationKind const&amp;, llvm::MutableArrayRef&lt;clang::Expr*&gt;, clang::QualType*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b93f2)
#<!-- -->24 0x00000000062b5114 clang::Sema::ActOnUninitializedDecl(clang::Decl*) (.part.0) SemaDecl.cpp:0:0
#<!-- -->25 0x0000000005f872d6 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&amp;, clang::Parser::ParsedTemplateInfo const&amp;, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f872d6)
#<!-- -->26 0x0000000005f96170 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&amp;, clang::DeclaratorContext, clang::ParsedAttributes&amp;, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f96170)
#<!-- -->27 0x0000000005f5f42b clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec&amp;, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f5f42b)
#<!-- -->28 0x0000000005f5fbb1 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f5fbb1)
#<!-- -->29 0x0000000005f66e66 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f66e66)
#<!-- -->30 0x0000000005f67d0d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr&lt;clang::DeclGroupRef&gt;&amp;, clang::Sema::ModuleImportState&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f67d0d)
#<!-- -->31 0x0000000005f5acfa clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5f5acfa)
#<!-- -->32 0x000000000401e378 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x401e378)
#<!-- -->33 0x000000000428a9b9 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x428a9b9)
#<!-- -->34 0x0000000004208c9e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4208c9e)
#<!-- -->35 0x000000000436974e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x436974e)
#<!-- -->36 0x0000000000c01496 cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc01496)
#<!-- -->37 0x0000000000bf8d2a ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->38 0x000000000405f3a9 void llvm::function_ref&lt;void ()&gt;::callback_fn&lt;clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const::'lambda'()&gt;(long) Job.cpp:0:0
#<!-- -->39 0x00000000036e4084 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x36e4084)
#<!-- -->40 0x000000000405f99f clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const (.part.0) Job.cpp:0:0
#<!-- -->41 0x0000000004027c05 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4027c05)
#<!-- -->42 0x000000000402866d clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x402866d)
#<!-- -->43 0x0000000004030585 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4030585)
#<!-- -->44 0x0000000000bfe90c clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbfe90c)
#<!-- -->45 0x0000000000af7a71 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xaf7a71)
#<!-- -->46 0x00007f0798c29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#<!-- -->47 0x00007f0798c29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#<!-- -->48 0x0000000000bf880e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbf880e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

[hokein]

The AST for the struct foo is:

TranslationUnitDecl
|- ...
|--CXXRecordDecl  foo
     |-...
     |-FieldDecl size 'T'
     | `-IntegerLiteral 'int' 0 

The CXXRecordDecl is ill-formed: it is a valid decl, and it has a FieldDecl with a dangling dependent type.
I think we should at least mark it as invalid (doing the invalidation at https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaType.cpp#L3837 is too late, the definition of CXXRecordDecl at this point is completed, we can't call setInvalidDecl()), or just drop it.

[shafik]

Looks like this regressed after clang-12: https://godbolt.org/z/x17zaM7oM

It looks like if it is too late in GetTypeSourceInfoForDeclarator then perhaps we can diagnose this in Parser::ParseTypeName

[shafik]

I think we need to mark it invalid here:

llvm-project/clang/lib/Parse/ParseDecl.cpp

Line 4386 in 41d19fb

tok::TokenKind Kind = Tok.getKind();

but we would need to add DeclSpecContext::DSC_alias_template_declaration to tell when we are in a alias template b/c right now we treat them both as DeclSpecContext::DSC_alias_declaration.

Then we could do something like this:

if (DSContext == DeclSpecContext::DSC_alias_template_declaration) {
         isInvalid = true;
          PrevSpec = Tok.getIdentifierInfo()->getNameStart();
          DiagID = diag::err_type_defined_in_alias_template;
          break;
      }

which works but breaks two tests b/c of additional diagnostics. Additional work may be needed to get this into shape.

CC @zygoloid @cor3ntin