code: public VarSymbol resolveInternalField(DiagnosticPosition pos, Env<AttrContext> env,
                                            Type site, Name name) {
          Symbol sym = findField(env, site, name, site.tsym);
          if (sym.kind == VAR) return (VarSymbol)sym;
          else throw new FatalError(
                   diags.fragment("fatal.err.cant.locate.field",
                                  name));
      }
docs: Resolve a field identifier, throw a fatal error if not found.
  @param pos       The position to use for error reporting.
  @param env       The environment current at the method invocation.
  @param site      The type of the qualifying expression, in which
  identifier is searched.
  @param name      The identifier's name.