> IDEs like Cursive provide advanced static analysis and refactoring support.

Can you give an example? Would these tools allow you to define a custom type with fields and ensure it is correct everywhere at compile time like a static language?

While Clojure is dynamically typed, tools like clj-kondo, Cursive and clojure-lsp can offer some static analysis benefit like warning about undefined vars or functions. There isn't "true" static checking, but you can use Spec and Malli for runtime checking. That doesn't provide same level of compile-time guaranties as statically type language, yet it offers some unique capabilities that many statically typed languages struggle to match, like

- Dynamic predicates - Spec allows you to define types using arbitrary predicates, which can be more expressive than traditional static type systems;

- Runtime generative testing - Spec can automatically generate test data based on your specifications, which is powerful for property-based testing;

- Flexible validation - You can validate complex nested data structures and apply specs selectively, which is often more flexible than static type checking;

- Extensibility - Specs can be added to existing types without modifying their source, and data-driven nature of it - Specs are just data and can be manipulated programmatically.

Yep, I'd add these advantages that schema systems have:

- Power - you can do arbitrary checks on the data, static type systems are quite weak in what kind of properties they can verify (far from turing complete)

- Flexibility to do checking at where you want at runtime (eg check data at API boundaries)

- Ability to treat schemas as data, generate them, output them as data and share between systems (for example in databases), throug conversions possible to interop with other platforms (eg json schema)

- loose coupling to your programming language, are just libraries