[skybrian]

Yes, like many refactorings, rewriting a function as an immutable class with a method is not always a win. It depends on how you want to group a function’s parameters, whether that grouping has an intuitive name, and whether you might want to write other methods that take the same initial parameters. Sometimes grouping parameters using a record type is better, though you don’t get the nice syntax.

If currying isn’t built-in, you can emulate it. In TypeScript you need to do it explicitly, which means anticipating that it will be used, and whenever I try that, I later decide that it’s needlessly obscure and rewrite the code some other way.

Even with built-in currying, you still need to anticipate usage by changing the order of the parameters, based on which ones you expect the callers to have first. It’s less general than writing an inline function with exactly the parameters you need. TypeScript has nice syntax for defining tiny, one-off functions and I think that’s better than having currying.

One side-effect of having currying in a language is that it discourages naming things, and I think that’s often bad for readability. A chain of method calls gives you a lot of names to look up and a place to put documentation.