default StringMatcher<R> toUpperCase() {
    return Matchers.extract(this).applyRaw(e -> Expressions.unaryCall(StringOperators.TO_UPPER_CASE, e)).create();
  }
Apply upper case function to current expression (equivalent to {@code $this.toUpperCase()})
criteria/common/src/org/immutables/criteria/matcher/StringMatcher.java