QV4::IR::IRDecoder::visitMove asserts with message "QtQmlViewer(15098)/(default) qt_assert: ASSERT: "m->kind != IR::Member::MemberOfEnum && m->kind != IR::Member::MemberOfIdObjectsArray" in file compiler/qv4isel_p.cpp, line 139", when it compiles e.g. the minimal example you'll find attached.
The most relevant line is "onBar: foo = bottom". The crash happens if the id of the object I assign to foo here, is one of "top", "bottom", "left", "right", "horizontalCenter" or "verticalCenter". It doesn't happen for e.g. "centerIn" or any other id.
Moreover it doesn't happen if foo is of type QtObject.
The semantic issues in the qml file are to make it as small as possible, it happens for valid files as well.