C++ compiler error when bitfield field converted to value

[bbannier]

In the &convert attribute we support any RHS expressions which produce a value, i.e., the RHS can e.g., be a function, a value, or a literal. This got broken for bitfield fields with #1492 (in particular f3a8bdf).

module foo;

public type X = unit {
    : uint8 &convert="foo"; # WORKS.

    : bitfield(8) {
        a: 0..7 &convert=FOO(); # WORKS.
    };

    : bitfield(8) {
        b: 0..7 &convert=FOO2; # BROKEN.
    };

    : bitfield(8) {
        c: 0..7 &convert=FOO3; # BROKEN.
    };

    : bitfield(8) {
        d: 0..7 &convert="foo"; # BROKEN.
    };
};

function FOO(): string { return "foo"; }
const FOO2 = "foo";
global FOO3 = "foo";

$ spicyc -dj foo.spicy
/private/var/folders/ht/vtb0rkbd4ws15vx02xdb84zw0000gn/T/foo_1c0ff69c973b5abc-2ab7850513fcbfef.cc:74:136: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]
    const ::hilti::rt::TypeInfo __ti_bitfieldx2a8x2b_x73__d_0_7_x28convertx31_foo_x3e_x75 = { {}, "bitfield(8) {     d: 0..7 &convert="foo"; }", new ::hilti::rt::type_info::Bitfield(std::vector<::hilti::rt::type_info::bitfield::Bits>({::hilti::rt::type_info::bitfield::Bits{ "d", &::hilti::rt::type_info::string, hilti::rt::bitfield::elementOffset<hilti::rt::Bitfield<std::string, ::hilti::rt::integer::safe<uint8_t>>, 0>() }})) };
                                                                                                                                       ^
                                                                                                                                        
/private/var/folders/ht/vtb0rkbd4ws15vx02xdb84zw0000gn/T/foo_1c0ff69c973b5abc-2ab7850513fcbfef.cc:74:136: error: expected '}'
/private/var/folders/ht/vtb0rkbd4ws15vx02xdb84zw0000gn/T/foo_1c0ff69c973b5abc-2ab7850513fcbfef.cc:74:93: note: to match this '{'
    const ::hilti::rt::TypeInfo __ti_bitfieldx2a8x2b_x73__d_0_7_x28convertx31_foo_x3e_x75 = { {}, "bitfield(8) {     d: 0..7 &convert="foo"; }", new ::hilti::rt::type_info::Bitfield(std::vector<::hilti::rt::type_info::bitfield::Bits>({::hilti::rt::type_info::bitfield::Bits{ "d", &::hilti::rt::type_info::string, hilti::rt::bitfield::elementOffset<hilti::rt::Bitfield<std::string, ::hilti::rt::integer::safe<uint8_t>>, 0>() }})) };
                                                                                            ^
In file included from /private/var/folders/ht/vtb0rkbd4ws15vx02xdb84zw0000gn/T/foo_1c0ff69c973b5abc-2ab7850513fcbfef.cc:1:
In file included from /Users/bbannier/src/spicy/hilti/runtime/include/hilti/rt/libhilti.h:9:
In file included from /Users/bbannier/src/spicy/build/include/hilti/rt/autogen/config.h:5:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/string:576:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/string_view:1027:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/functional:515:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/__functional/boyer_moore_searcher.h:25:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/unordered_map:530:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/__node_handle:65:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/optional:646:5: error: static assertion failed due to requirement '!is_reference_v<const std::string &>': instantiation of optional with a reference type is ill-formed
    static_assert(!is_reference_v<value_type>,
    ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/__type_traits/is_empty.h:23:38: note: in instantiation of template class 'std::optional<const std::string &>' requested here
    : public integral_constant<bool, __is_empty(_Tp)> {};
                                     ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/tuple:273:16: note: in instantiation of template class 'std::is_empty<std::optional<const std::string &>>' requested here
          bool=is_empty<_Hp>::value && !__libcpp_is_final<_Hp>::value
               ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/tuple:480:14: note: in instantiation of default argument for '__tuple_leaf<0UL, std::optional<const std::string &>>' required here
    : public __tuple_leaf<_Indx, _Tp>...
             ^~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/tuple:570:12: note: in instantiation of template class 'std::__tuple_impl<std::__tuple_indices<0, 1>, std::optional<const std::string &>, std::optional<SafeInt<unsigned char, hilti::rt::integer::detail::SafeIntException>>>' requested here
    _BaseT __base_;
           ^
/Users/bbannier/src/spicy/hilti/runtime/include/hilti/rt/types/bitfield.h:26:38: note: in instantiation of template class 'std::tuple<std::optional<const std::string &>, std::optional<SafeInt<unsigned char, hilti::rt::integer::detail::SafeIntException>>>' requested here
    std::tuple<std::optional<Ts>...> value;
                                     ^
/private/var/folders/ht/vtb0rkbd4ws15vx02xdb84zw0000gn/T/foo_1c0ff69c973b5abc-2ab7850513fcbfef.cc:163:229: note: in instantiation of template class 'hilti::rt::Bitfield<const std::string &, SafeInt<unsigned char, hilti::rt::integer::detail::SafeIntException>>' requested here
    std::tie(::hilti::rt::optional::valueOrInit((*__self)._anon_3), __cur) = (__x_2 = ::hilti::rt::integer::unpack<uint8_t>(__cur, ::hilti::rt::ByteOrder{::hilti::rt::ByteOrder::Network}), hilti::rt::make_result(std::make_tuple(hilti::rt::make_bitfield(__hlt::foo::FOO2, hilti::rt::integer::noop(std::get<0>(*__x_2))), std::get<1>(*__x_2)))).valueOrThrow();
                                                                                                                                                                                                                                    ^
In file included from /private/var/folders/ht/vtb0rkbd4ws15vx02xdb84zw0000gn/T/foo_1c0ff69c973b5abc-2ab7850513fcbfef.cc:1:
In file included from /Users/bbannier/src/spicy/hilti/runtime/include/hilti/rt/libhilti.h:9:
In file included from /Users/bbannier/src/spicy/build/include/hilti/rt/autogen/config.h:5:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/string:576:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/string_view:1027:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/functional:515:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/__functional/boyer_moore_searcher.h:25:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/unordered_map:530:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/__node_handle:65:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/optional:646:5: error: static assertion failed due to requirement '!is_reference_v<std::string &>': instantiation of optional with a reference type is ill-formed
    static_assert(!is_reference_v<value_type>,
    ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/__type_traits/is_empty.h:23:38: note: in instantiation of template class 'std::optional<std::string &>' requested here
    : public integral_constant<bool, __is_empty(_Tp)> {};
                                     ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/tuple:273:16: note: in instantiation of template class 'std::is_empty<std::optional<std::string &>>' requested here
          bool=is_empty<_Hp>::value && !__libcpp_is_final<_Hp>::value
               ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/tuple:480:14: note: in instantiation of default argument for '__tuple_leaf<0UL, std::optional<std::string &>>' required here
    : public __tuple_leaf<_Indx, _Tp>...
             ^~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/include/c++/v1/tuple:570:12: note: in instantiation of template class 'std::__tuple_impl<std::__tuple_indices<0, 1>, std::optional<std::string &>, std::optional<SafeInt<unsigned char, hilti::rt::integer::detail::SafeIntException>>>' requested here
    _BaseT __base_;
           ^
/Users/bbannier/src/spicy/hilti/runtime/include/hilti/rt/types/bitfield.h:26:38: note: in instantiation of template class 'std::tuple<std::optional<std::string &>, std::optional<SafeInt<unsigned char, hilti::rt::integer::detail::SafeIntException>>>' requested here
    std::tuple<std::optional<Ts>...> value;
                                     ^
/private/var/folders/ht/vtb0rkbd4ws15vx02xdb84zw0000gn/T/foo_1c0ff69c973b5abc-2ab7850513fcbfef.cc:186:229: note: in instantiation of template class 'hilti::rt::Bitfield<std::string &, SafeInt<unsigned char, hilti::rt::integer::detail::SafeIntException>>' requested here
    std::tie(::hilti::rt::optional::valueOrInit((*__self)._anon_4), __cur) = (__x_3 = ::hilti::rt::integer::unpack<uint8_t>(__cur, ::hilti::rt::ByteOrder{::hilti::rt::ByteOrder::Network}), hilti::rt::make_result(std::make_tuple(hilti::rt::make_bitfield((*__hlt::foo::FOO3), hilti::rt::integer::noop(std::get<0>(*__x_3))), std::get<1>(*__x_3)))).valueOrThrow();
                                                                                                                                                                                                                                    ^
4 errors generated.
[error] spicyc: JIT compilation failed