code: def destructuring_stmt_handle(self, original, loc, tokens):
          
          internal_assert(len(tokens) == 2, "invalid destructuring assignment tokens", tokens)
          matches, item = tokens
          out = match_handle(loc, [matches, "in", item, None])
          out += self.pattern_error(original, loc, match_to_var, match_check_var)
          return out
docs: Process match assign blocks.