I recently merged linear let- and where-bindings in GHC. Which means that we’ll have these in GHC 9.10, which is cause for celebration for me. Though they are much overdue, so maybe I should instead apologise to you.

Anyway, I thought I’d take the opportunity to discuss some of GHC’s inner workings and how they explain some of the features of linear types in Haskell. We’ll be discussing a frequently asked question: why can’t Ur be a newtype? And some new questions such as: why must linear let-bindings have a !? But first…