As programmers, we are very incautious with our use of the word “type”. The concept of “type” is sufficiently abstract and specific that we are tempted to understand it by analogy, so much that we begin to confuse analogy with sameness. The colloquial “runtime type”, a fair approximation of “class”, makes it tempting to equate types with “classes, interfaces, traits, that sort of thing”, which I will name classes for the rest of this article. But they aren’t the same. Th...
