• Turn the given error into a human-readable string. Expects the string to be printed, so if RUSTC_CTFE_BACKTRACE is set this will show a backtrace of the rustc internals that triggered the error.
  • Use the already known layout if given (but sanity check in debug mode), or compute the layout.
  • Test if it is valid for a MIR assignment to assign src-typed place to dest-typed value. This test should be symmetric, as it is primarily about layout compatibility.