LobstersThursday · May 21, 2026FREE

Erasing Existentials

The blog post on wolfgirl.dev explores a method to erase existential types during compilation, removing the runtime cost associated with them. Existentials, which allow hiding type information, typically require boxing or dynamic dispatch. The proposed technique leverages type-directed transformations to replace existentials with concrete types where possible, reducing memory and CPU overhead. The author demonstrates this with examples in a Haskell-like language, showing how erased existentials lead to simpler generated code. The approach is still experimental but promises significant optimizations for functional programs that rely on existential quantification. The post was published on May 20, 2026, and has generated discussion on Lobsters about trade-offs and implementation challenges.