Delegate declarations

Delegates give a name to a particular kind of function. Use them when an API accepts or stores callbacks with a shared signature. The declaration lists the parameters and optional return type, and the compiler creates the corresponding delegate members.

delegate Transformer(value: int) -> string

class Pipeline {
    delegate Stage<T>(ref value: T) -> bool
}

Delegates are emitted as sealed, abstract types that inherit from System.MulticastDelegate. For every delegate declaration, the compiler synthesizes:

• A constructor .ctor(object, IntPtr) that binds a target and method pointer.
• An Invoke method whose parameters (including any ref/out/in modifiers) and return type match the declaration.

The synthesized Invoke method also preserves parameter lifetime metadata. In particular, scoped parameters emit ScopedRefAttribute when required, including parameters that use generic types permitting ref-like arguments.

If the return type clause is omitted, the delegate returns unit. Delegate declarations support generic type parameters and constraints using the same where clause rules as other type declarations. Accessibility follows the standard type rules: namespace-level delegates default to internal and require public to be exported from the assembly, while nested delegates default to public.