@Great_Albums @lowqualityfacts it's "whoever", not "whomever" because it's the nominative case (as in Latin, German, etc.) which I just learned is also named the subjective case in English. The nominative case applies to the subject but also to the complement if the complement is the same thing as the subject. For example, in "I am a Berliner", both "I" and "a Berliner" use the nominative case because they describe the same thing. However, in "I eat a Berliner", "a Berliner" is not equivalent to the subject and therefore uses another case. This is poorly explained here and there:
https://en.wikipedia.org/wiki/Nominative_case
https://en.wikipedia.org/wiki/Predicative_expression