Using core.typed to guide runtime behavior?

[James MacAulay]

I'm interested in exploring the use of the types provided by core.typed to guide function behavior at runtime. Specifically, I'd like to wrap existing functions such that the resulting functions behave in different ways depending on the type signatures of each original function.

I'm imagining a setup where I have macros that get type information from core.typed at the time of macro-expansion, and either:

* decide entirely at macro-expansion time how a function should be wrapped based on its type, or

* somehow make the type information available at runtime, leaving the analysis of the types to runtime functions.

As an example of the kind of decision I'd like to make based on types, I might look at `clojure.core/map` and say "I'll wrap `map` such that its first argument will be transformed in some particular way because the argument is a function, and the rest of the arguments will be transformed in some other way because they are collections." The reason I want to have type information for this is that I want the transformations to be dependent on the actual semantics of the original function, which is hinted at by the types. For example I can take the fact that an argument's type is some sort of collection and infer that the function is probably processing its contents; in that case I would want to transform the argument in a different way than if its type were `Any`, in which case I could conclude that even if the argument ends up being a collection at runtime, the original function must not be relying on that fact.

Does anyone see any obvious pitfalls with this kind of thing? Any tips from the crowd? I'm not sure exactly the best way of actually "analyzing" the type signatures, but I'm hoping that I might find some tools for that in core.typed.

Thanks for any help you can give!

Cheers,

James

[Ambrose Bonnaire-Sergeant]

I haven't tried anything like this.

The most obvious pitfall is core.typed currently loads lazily and collects

type annotations only after check-ns.

There's a bunch of tools for manipulating types in the checker.

Thanks,

Ambrose

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[James MacAulay]

Thanks for the pointers, Ambrose, and thanks for core.typed!

James