There are 2 components here. One is the "type metaprogramming" - (mis)use of the type system to implement to do compile-time computation, mainly by using parametrized types as kinda-functions + type inference for kinda-pattern-matching.
The other is building up basic "data types" by pretty standard lambda calculus > LISP route. "Understanding Computation" book has a great chapter 6 on that, which is available in blog & video forms on https://computationbook.com/extras - Here, Church numerals were used to represent numbers. - booleans & conditionals here didn't resort to the lambda representation you'll see in the book, but relied on type conditionals builtin to TypeScript. - The names "Cons" & "nil" are a ringer for LISP-like building of lists, and recursive processing of lists, from a "pair" data type.