[justinpombrio]

Totally agree. I should have said "add sufficient annotations to distinguish shared references from mutable references", and "occassionally need to splatter confusing lifetime annotations all over the place".

EDIT: What's really relevant is that you can look at a Rust type, and tell whether it's shared, mutable, or owned; this is what Rust's borrow checker derives its power from. Likewise, Haskell's type system derives its (equally amazing) powers from the fact that you can look at a Haskell function's type signature, and tell what kinds of side effects it has. (Sometimes people think that Haskell functions don't have side effects in the sense that they never mutate anything. This is wrong; Haskell has mutable arrays in its standard library. Rather, it's that all side effects are reflected in a function's type signature.) https://hackage.haskell.org/package/array-0.5.4.0/docs/Data-...

I write Rust code for work, and we have a large codebase. We manage it pretty well, but there are definitely still innocuous looking changes that require adding lifetime annotations all over the place to avoid confusing error messages.

Rust is my favorite language by far (I get the impression you like it too and are defending it). I think the costs of its borrow checker are worth it, but they are significant costs.