How does 'Tail Recursive Conditional Types' work in TS 4.5+?

Tail recursion allows the compiler to handle much deeper recursive type instantiations without hitting the recursion limit.

Before TS 4.5, recursive conditional types had a strict limit (usually around 50 levels). If a type called itself, it consumed stack space. TS 4.5 introduced tail-call optimization for types. If the recursive call is in the 'return' position of the conditional (the tail), the compiler flattens the execution. This allows for complex types like deep string splitting or massive array flattening that were previously impossible.