Seems like this is related to Abstract def inside module not being enforced , but then again not: module Sth # there is no abstract module in Crystal abstract def magic : Int32 # this is not enforced by Crystal (only typos here will trigger a compile error) def twice_ma…

What is the issue in the pasted code? X implements magic, and it has the correct return type. So why would you expect a compile time error here? # a non-abstract class would trigger a compile error here (without the abstract(s) above) I assume you mean module there? That is just how modules work -…

An abstract class is a class that cannot be instantiated. Modules are already non-instantiable, so maybe that’s why there’s no abstract keyword for them. Are you actually looking for something like an interface, protocol, or trait, rather than an abstract module ? In Ruby, it’s common to write te…

I think I was too quick in my initial post. Let’s try to get it more straight. If we define an abstract class… abstract class X abstract def x def y z() end end … the compiler will… a) always complain if x is not defined by the subclass and b) complain about missing z if y i…

Abstract methods are entirely optional. They serve to document interfaces and validate their implementations. But they’re never required to type a program. Assuming a valid program, dropping all abstract defs should produce exactly the same output. So yeah this is on purpose. Crystal uses duck-typi…

Thanks, I think I get your point. Either the compiler chokes on something it cannot fulfill - or it spills out a binary. Non-fulfillability can arise out of methods or variables having incompatible types vs. use cases. Crystal enforces as little typing as possible, but allows arbitrary much of it. …

Why are there no abstract modules?

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straight-shoota February 23, 2025, 2:25pm 4

Also please note that the behaviour described in Abstract def inside module not being enforced has since been fixed. The compiler now refuses non-matching signatures.

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Why are there no abstract modules?

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