[llvm-bugs] [Bug 44671] New: Assertion failure while parsing deduction guide for class template with constructor constrained with terse syntax

Sun Jan 26 11:59:13 PST 2020

https://bugs.llvm.org/show_bug.cgi?id=44671

            Bug ID: 44671
           Summary: Assertion failure while parsing deduction guide for
                    class template with constructor constrained with terse
                    syntax
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++2a
          Assignee: unassignedclangbugs at nondot.org
          Reporter: david at doublewise.net
                CC: blitzrakete at gmail.com, erik.pilkington at gmail.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk

The following code:

```
template <class> concept C = true;

template <class T> struct S {
    template <C U> S(U) {}
};

template <class T> S(T&) -> S<T>;
```

causes clang to crash with

```
Stack dump:

0.      Program arguments: /home/david/llvm/build/bin/clang++ -g -o
/tmp/compiler-explorer-compiler120026-63259-1qt3j0r.jjink/output.s -mllvm
--x86-asm-syntax=intel -S -std=c++2a -fcolor-diagnostics -fno-crash-diagnostics
<source> 

1.      <source>:7:33: current parser token ';'

 #0 0x0000561bb63b47e2 PrintStackTraceSignalHandler(void*)
(/home/david/llvm/build/bin/clang+++0x31f27e2)

 #1 0x0000561bb63b214e llvm::sys::RunSignalHandlers()
(/home/david/llvm/build/bin/clang+++0x31f014e)

 #2 0x0000561bb63b3867 llvm::sys::CleanupOnSignal(unsigned long)
(/home/david/llvm/build/bin/clang+++0x31f1867)

 #3 0x0000561bb632ea5e (anonymous
namespace)::CrashRecoveryContextImpl::HandleCrash(int, unsigned long)
(/home/david/llvm/build/bin/clang+++0x316ca5e)

 #4 0x0000561bb632ec04 CrashRecoverySignalHandler(int)
(/home/david/llvm/build/bin/clang+++0x316cc04)

 #5 0x00007f37d89a5930 __restore_rt (/usr/lib/libpthread.so.0+0x14930)

 #6 0x0000561bb86531eb (anonymous
namespace)::ConvertConstructorToDeductionGuideTransform::transformConstructor(clang::FunctionTemplateDecl*,
clang::CXXConstructorDecl*) (/home/david/llvm/build/bin/clang+++0x54911eb)

 #7 0x0000561bb8652911
clang::Sema::DeclareImplicitDeductionGuides(clang::TemplateDecl*,
clang::SourceLocation) (/home/david/llvm/build/bin/clang+++0x5490911)

 #8 0x0000561bb84c981b LookupDirect(clang::Sema&, clang::LookupResult&,
clang::DeclContext const*) (/home/david/llvm/build/bin/clang+++0x530781b)

 #9 0x0000561bb84c4b26 clang::Sema::CppLookupName(clang::LookupResult&,
clang::Scope*) (/home/david/llvm/build/bin/clang+++0x5302b26)

#10 0x0000561bb84c91c5 clang::Sema::LookupName(clang::LookupResult&,
clang::Scope*, bool) (/home/david/llvm/build/bin/clang+++0x53071c5)

#11 0x0000561bb8150a15 clang::Sema::HandleDeclarator(clang::Scope*,
clang::Declarator&, llvm::MutableArrayRef<clang::TemplateParameterList*>)
(/home/david/llvm/build/bin/clang+++0x4f8ea15)

#12 0x0000561bb86718b8 clang::Sema::ActOnTemplateDeclarator(clang::Scope*,
llvm::MutableArrayRef<clang::TemplateParameterList*>, clang::Declarator&)
(/home/david/llvm/build/bin/clang+++0x54af8b8)

#13 0x0000561bb7f42316
clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&,
clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*)
(/home/david/llvm/build/bin/clang+++0x4d80316)

#14 0x0000561bb7f436a5
clang::Parser::ParseDeclarationAfterDeclarator(clang::Declarator&,
clang::Parser::ParsedTemplateInfo const&)
(/home/david/llvm/build/bin/clang+++0x4d816a5)

#15 0x0000561bb7fb9bb3
clang::Parser::ParseSingleDeclarationAfterTemplate(clang::DeclaratorContext,
clang::Parser::ParsedTemplateInfo const&, clang::ParsingDeclRAIIObject&,
clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier)
(/home/david/llvm/build/bin/clang+++0x4df7bb3)

#16 0x0000561bb7fb87ae
clang::Parser::ParseTemplateDeclarationOrSpecialization(clang::DeclaratorContext,
clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier)
(/home/david/llvm/build/bin/clang+++0x4df67ae)

#17 0x0000561bb7fb801e
clang::Parser::ParseDeclarationStartingWithTemplate(clang::DeclaratorContext,
clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier)
(/home/david/llvm/build/bin/clang+++0x4df601e)

#18 0x0000561bb7f3b5ad
clang::Parser::ParseDeclaration(clang::DeclaratorContext,
clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&,
clang::SourceLocation*) (/home/david/llvm/build/bin/clang+++0x4d795ad)

#19 0x0000561bb7f0f5cf
clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&,
clang::ParsingDeclSpec*) (/home/david/llvm/build/bin/clang+++0x4d4d5cf)

#20 0x0000561bb7f0dd37
clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, bool)
(/home/david/llvm/build/bin/clang+++0x4d4bd37)

#21 0x0000561bb7f08f6d clang::ParseAST(clang::Sema&, bool, bool)
(/home/david/llvm/build/bin/clang+++0x4d46f6d)

#22 0x0000561bb6dee594 clang::CodeGenAction::ExecuteAction()
(/home/david/llvm/build/bin/clang+++0x3c2c594)

#23 0x0000561bb6d2e9c6 clang::FrontendAction::Execute()
(/home/david/llvm/build/bin/clang+++0x3b6c9c6)

#24 0x0000561bb6c817f3
clang::CompilerInstance::ExecuteAction(clang::FrontendAction&)
(/home/david/llvm/build/bin/clang+++0x3abf7f3)

#25 0x0000561bb6de9078
clang::ExecuteCompilerInvocation(clang::CompilerInstance*)
(/home/david/llvm/build/bin/clang+++0x3c27078)

#26 0x0000561bb52fd4ff cc1_main(llvm::ArrayRef<char const*>, char const*,
void*) (/home/david/llvm/build/bin/clang+++0x213b4ff)

#27 0x0000561bb52fb48d ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&)
(/home/david/llvm/build/bin/clang+++0x213948d)

#28 0x0000561bb6b33532 void llvm::function_ref<void
()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optional<llvm::StringRef>
>, std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> >*, bool*) const::$_1>(long)
(/home/david/llvm/build/bin/clang+++0x3971532)

#29 0x0000561bb632e9aa
llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>)
(/home/david/llvm/build/bin/clang+++0x316c9aa)

#30 0x0000561bb6b32995
clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optional<llvm::StringRef>
>, std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> >*, bool*) const
(/home/david/llvm/build/bin/clang+++0x3970995)

#31 0x0000561bb6afd22b
clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&,
clang::driver::Command const*&) const
(/home/david/llvm/build/bin/clang+++0x393b22b)

#32 0x0000561bb6afd67a
clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&,
llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*> >&) const
(/home/david/llvm/build/bin/clang+++0x393b67a)

#33 0x0000561bb6b15c17
clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&,
llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*> >&)
(/home/david/llvm/build/bin/clang+++0x3953c17)

#34 0x0000561bb52fabf7 main (/home/david/llvm/build/bin/clang+++0x2138bf7)

#35 0x00007f37d840c153 __libc_start_main (/usr/lib/libc.so.6+0x27153)

#36 0x0000561bb52f802e _start (/home/david/llvm/build/bin/clang+++0x213602e)

clang++: /home/david/llvm/clang/lib/Parse/Parser.cpp:444: virtual
clang::Parser::~Parser(): Assertion `TemplateIds.empty() && "Still alive
TemplateIdAnnotations around?"' failed.

Compiler returned: -1
```

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