scala.caps

Carrier trait for capture set type parameters

Base trait for classes that represent capabilities in the object-capability model.

A capability is a value representing a permission, access right, resource or effect. Capabilities are typically passed to code as parameters; they should not be global objects. Often, they come with access restrictions such as scoped lifetimes or limited sharing.

An example is the Label class in scala.util.boundary. It represents a capability in the sense that it gives permission to break to the enclosing boundary represented by the Label. It has a scoped lifetime, since breaking to a Label after the associated boundary was exited gives a runtime exception.

Capability has a formal meaning when Capture Checking is turned on. But even without capture checking, extending this trait can be useful for documenting the intended purpose of a class.

Capability has exactly two subtraits: Shared and Exclusive.

A marker trait for classifier capabilities that can appear in .only qualifiers. Capability classes directly extending Classifier are treated as classifier capbilities

A type constraint expressing that the capture set C needs to contain the capability R

Base trait for capabilities that capture some continuation or return point in the stack. Examples are exceptions, labels, Async, CanThrow.

Marker trait for exclusive capabilities that are separation-checked

A trait that used to allow expressing existential types. Replaced by root.Result instances.

Marker trait for classes with methods that require an exclusive reference.

Marker trait for classes with reader methods, typically extended by Mutable classes

Marker trait for capabilities that can be safely shared in a concurrent context. During separation checking, shared capabilities are not taken into account.

The universal capture reference.

An annotations on parameters and update methods. On a parameter it states that any capabilties passed in the argument are no longer available afterwards, unless they are of class SharableCapabilitty. On an update method, it states that the this of the enclosing class is consumed, which means that any capabilities of the method prefix are no longer available afterwards.

An annotation on parameters x stating that the method's body makes use of the reach capability x*. Consequently, when calling the method we need to charge the deep capture set of the actual argiment to the environment.

Note: This should go into annotations. For now it is here, so that we can experiment with it quickly between minor releases