[concepts] [ice] substitution into constraint expression resulted in a non-constant expression

[marehr]

Bugzilla Link	51503
Version	trunk
OS	Linux
CC	@AaronBallman,@JohelEGP,@zygoloid

Extended Description

Hi clang-team,

the following code does not compile with clang trunk:

template <typename urng_t>
struct contiguous_range
{
    template <bool const_range>
        requires (const_range == false)
    using basic_iterator = int;

    auto begin()
    {
        return basic_iterator<false>{};
    }
};

https://godbolt.org/z/jobYveoe3

with the error

<source>:5:19: error: substitution into constraint expression resulted in a non-constant expression
        requires (const_range == false)
                  ^~~~~~~~~~~~~~~~~~~~
<source>:10:16: note: while checking constraint satisfaction for template 'basic_iterator<false>' required here
        return basic_iterator<false>{};
               ^~~~~~~~~~~~~~~~~~~~~
<source>:5:19: note: subexpression not valid in a constant expression
        requires (const_range == false)
                  ^

MSVC 16.11, and gcc 11.2 are able to compile this code. A curious side note: If you remove template <typename urng_t> clang does compile this code snippet.

[marehr]

I played with this a bit more and got an ICE out of it.

template <bool const_range, bool const_convertible>
concept const_convertible_guard = const_range == false || const_convertible;

template <typename urng_t>
struct contiguous_range
{
    template <bool const_range>
        requires const_convertible_guard<const_range, false>
    using basic_iterator = int;

    auto begin()
    {
        return basic_iterator<false>{};
    }
};

https://godbolt.org/z/x11TfeaME

with the stack trace:

PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-trunk/bin/clang++ -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++20 <source>
1.	<source>:13:16: at annotation token
2.	<source>:5:1: parsing struct/union/class body 'contiguous_range'
3.	<source>:12:5: parsing function body 'contiguous_range::begin'
4.	<source>:12:5: in compound statement ('{}')
 #&#8203;0 0x0000558a7521336f PrintStackTraceSignalHandler(void*) Signals.cpp:0:0
 #&#8203;1 0x0000558a75211230 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x34fe230)
 #&#8203;2 0x0000558a75162218 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #&#8203;3 0x00007fe120fc23c0 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x153c0)
 #&#8203;4 0x0000558a77bf42f9 clang::StmtVisitorBase<llvm::make_const_ptr, (anonymous namespace)::IntExprEvaluator, bool>::Visit(clang::Stmt const*) ExprConstant.cpp:0:0
 #&#8203;5 0x0000558a77bfa8e5 Evaluate(clang::APValue&, (anonymous namespace)::EvalInfo&, clang::Expr const*) ExprConstant.cpp:0:0
 #&#8203;6 0x0000558a77c0af26 EvaluateInPlace(clang::APValue&, (anonymous namespace)::EvalInfo&, (anonymous namespace)::LValue const&, clang::Expr const*, bool) ExprConstant.cpp:0:0
 #&#8203;7 0x0000558a77c12b39 clang::Expr::EvaluateAsConstantExpr(clang::Expr::EvalResult&, clang::ASTContext const&, clang::Expr::ConstantExprKind) const (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5effb39)
 #&#8203;8 0x0000558a771d6532 bool calculateConstraintSatisfaction<calculateConstraintSatisfaction(clang::Sema&, clang::NamedDecl const*, llvm::ArrayRef<clang::TemplateArgument>, clang::SourceLocation, clang::MultiLevelTemplateArgumentList&, clang::Expr const*, clang::ConstraintSatisfaction&)::'lambda'(clang::Expr const*)>(clang::Sema&, clang::Expr const*, clang::ConstraintSatisfaction&, calculateConstraintSatisfaction(clang::Sema&, clang::NamedDecl const*, llvm::ArrayRef<clang::TemplateArgument>, clang::SourceLocation, clang::MultiLevelTemplateArgumentList&, clang::Expr const*, clang::ConstraintSatisfaction&)::'lambda'(clang::Expr const*)&&) SemaConcept.cpp:0:0
 #&#8203;9 0x0000558a771d6ee0 clang::Sema::CheckConstraintSatisfaction(clang::NamedDecl const*, llvm::ArrayRef<clang::Expr const*>, llvm::ArrayRef<clang::TemplateArgument>, clang::SourceRange, clang::ConstraintSatisfaction&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x54c3ee0)
#&#8203;10 0x0000558a771df978 clang::Sema::EnsureTemplateArgumentListConstraints(clang::TemplateDecl*, llvm::ArrayRef<clang::TemplateArgument>, clang::SourceRange) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x54cc978)
#&#8203;11 0x0000558a776b32d5 clang::Sema::CheckTemplateArgumentList(clang::TemplateDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo&, bool, llvm::SmallVectorImpl<clang::TemplateArgument>&, bool, bool*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x59a02d5)
#&#8203;12 0x0000558a776b6097 clang::Sema::CheckTemplateIdType(clang::TemplateName, clang::SourceLocation, clang::TemplateArgumentListInfo&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x59a3097)
#&#8203;13 0x0000558a776b7d6f clang::Sema::ActOnTemplateIdType(clang::Scope*, clang::CXXScopeSpec&, clang::SourceLocation, clang::OpaquePtr<clang::TemplateName>, clang::IdentifierInfo*, clang::SourceLocation, clang::SourceLocation, llvm::MutableArrayRef<clang::ParsedTemplateArgument>, clang::SourceLocation, bool, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x59a4d6f)
#&#8203;14 0x0000558a7708983d clang::Parser::AnnotateTemplateIdTokenAsType(clang::CXXScopeSpec&, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x537683d)
#&#8203;15 0x0000558a76fc71d7 clang::Parser::TryAnnotateTypeOrScopeTokenAfterScopeSpec(clang::CXXScopeSpec&, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52b41d7)
#&#8203;16 0x0000558a76fc7dff clang::Parser::TryAnnotateTypeOrScopeToken() (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52b4dff)
#&#8203;17 0x0000558a77018550 clang::Parser::ParseCastExpression(clang::Parser::CastParseKind, bool, bool&, clang::Parser::TypeCastState, bool, bool*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5305550)
#&#8203;18 0x0000558a77019c26 clang::Parser::ParseCastExpression(clang::Parser::CastParseKind, bool, clang::Parser::TypeCastState, bool, bool*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5306c26)
#&#8203;19 0x0000558a77019cb8 clang::Parser::ParseAssignmentExpression(clang::Parser::TypeCastState) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5306cb8)
#&#8203;20 0x0000558a7701c109 clang::Parser::ParseExpression(clang::Parser::TypeCastState) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5309109)
#&#8203;21 0x0000558a770706bf clang::Parser::ParseReturnStatement() (/opt/compiler-explorer/clang-trunk/bin/clang+++0x535d6bf)
#&#8203;22 0x0000558a77076a7f clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::ParsedAttributesWithRange&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5363a7f)
#&#8203;23 0x0000558a77077c9d clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5364c9d)
#&#8203;24 0x0000558a77072842 clang::Parser::ParseCompoundStatementBody(bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x535f842)
#&#8203;25 0x0000558a77073673 clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5360673)
#&#8203;26 0x0000558a76fd4653 clang::Parser::ParseLexedMethodDef(clang::Parser::LexedMethod&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52c1653)
#&#8203;27 0x0000558a76fd4325 clang::Parser::ParseLexedMethodDefs(clang::Parser::ParsingClass&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52c1325)
#&#8203;28 0x0000558a7700f590 clang::Parser::ParseCXXMemberSpecification(clang::SourceLocation, clang::SourceLocation, clang::ParsedAttributesWithRange&, unsigned int, clang::Decl*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52fc590)
#&#8203;29 0x0000558a77011a83 clang::Parser::ParseClassSpecifier(clang::tok::TokenKind, clang::SourceLocation, clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, bool, clang::Parser::DeclSpecContext, clang::ParsedAttributesWithRange&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52fea83)
#&#8203;30 0x0000558a76ff3628 clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52e0628)
#&#8203;31 0x0000558a7709517a clang::Parser::ParseSingleDeclarationAfterTemplate(clang::DeclaratorContext, clang::Parser::ParsedTemplateInfo const&, clang::ParsingDeclRAIIObject&, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x538217a)
#&#8203;32 0x0000558a770999e3 clang::Parser::ParseTemplateDeclarationOrSpecialization(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x53869e3)
#&#8203;33 0x0000558a77099f54 clang::Parser::ParseDeclarationStartingWithTemplate(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5386f54)
#&#8203;34 0x0000558a76ff7ea5 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributesWithRange&, clang::SourceLocation*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52e4ea5)
#&#8203;35 0x0000558a76fcf14b clang::Parser::ParseExternalDeclaration(clang::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52bc14b)
#&#8203;36 0x0000558a76fd0549 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52bd549)
#&#8203;37 0x0000558a76fc3da9 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x52b0da9)
#&#8203;38 0x0000558a7616ac12 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-trunk/bin/clang+++0x4457c12)
#&#8203;39 0x0000558a75b16381 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3e03381)
#&#8203;40 0x0000558a75ab43e2 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3da13e2)
#&#8203;41 0x0000558a75be2713 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3ecf713)
#&#8203;42 0x0000558a72f9d10c cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x128a10c)
#&#8203;43 0x0000558a72f992dd ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&) driver.cpp:0:0
#&#8203;44 0x0000558a7595f1a5 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::'lambda'()>(long) Job.cpp:0:0
#&#8203;45 0x0000558a75162803 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x344f803)
#&#8203;46 0x0000558a7596125e clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optional<llvm::StringRef> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, bool*) const (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3c4e25e)
#&#8203;47 0x0000558a75936c9a clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&) const (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3c23c9a)
#&#8203;48 0x0000558a759377ef clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*> >&) const (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3c247ef)
#&#8203;49 0x0000558a75940bd5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*> >&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3c2dbd5)
#&#8203;50 0x0000558a72eb1f4e main (/opt/compiler-explorer/clang-trunk/bin/clang+++0x119ef4e)
#&#8203;51 0x00007fe120a720b3 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b3)
#&#8203;52 0x0000558a72f98e5a _start (/opt/compiler-explorer/clang-trunk/bin/clang+++0x1285e5a)
clang-14: error: clang frontend command failed with exit code 139 (use -v to see invocation)
Compiler returned: 139

[JohelEGP]

Here's an arguably better error message, from https://godbolt.org/z/8hMb3sc9Y:

In file included from /app/test.cpp:1:
mod.cpp:8:5: error: substitution into constraint expression resulted in a non-constant expression
    std::is_reference_v<DerivedRef> and
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test.cpp:3:25: note: while checking constraint satisfaction for template 'static_downcast<D &, B<D> &>' required here
  D& derived() { return mod::static_downcast<D&>(*this); }
                        ^~~
test.cpp:3:25: note: in instantiation of function template specialization 'mod::static_downcast<D &, B<D> &>' requested here
test.cpp:8:11: note: in instantiation of member function 'B<D>::derived' requested here
  (void)d.derived();
          ^
mod.cpp:8:5: note: initializer of 'is_reference_v<D &>' is unknown
    std::is_reference_v<DerivedRef> and
    ^
/opt/compiler-explorer/clang-trunk-20211012/bin/../include/c++/v1/type_traits:908:23: note: declared here
inline constexpr bool is_reference_v = __is_reference(_Tp);
                      ^

[JohelEGP]

Turns out I just didn't reexport imported header units used within templates (Bug 35395) in a module. It works otherwise: https://godbolt.org/z/od9sa6cdY.

[usx95]

Works as intended at trunk.
https://godbolt.org/z/K67bbMz3q

[llvmbot]

@llvm/issue-subscribers-clang-frontend