Function class_decl 

pub fn class_decl(
    ctx: &mut Context,
    cg: &mut RustCodegen,
    visibility: &Visibility,
    name: &Identifier,
    generics: &GenericsDecl,
    inherits: &Option<ExprPath>,
    fields: &Vec<Spanned<FieldDeclStmt>>,
    constructor: &Spanned<ClassConstructor>,
    items: &Vec<ClassItem>,
)