Additional Types

• These types can be used in the fields of shared structs and the arguments and returns of extern functions.
• Note that Rust’s String does not map directly to std::string. There are a few reasons for this:
  • std::string does not uphold the UTF-8 invariant that String requires.
  • The two types have different layouts in memory and so can’t be passed directly between languages.
  • std::string requires move constructors that don’t match Rust’s move semantics, so a std::string can’t be passed by value to Rust.