docs: protected MatchResult checkConsistent(Variable field, Variable value, BindingSet bindingSet) {
          // Ensure that the field and value variables are consistent with
          // previous definitions (if any)
          bindingSet = addOrCheckDefinition(fieldVarName, field, bindingSet);
          if (bindingSet == null) {
              return null;
          }
          bindingSet = addOrCheckDefinition(valueVarName, value, bindingSet);
          if (bindingSet == null) {
              return null;
          }
          return new MatchResult(this, bindingSet);
      }