Types

Types

This chapter describes the type system of Rue.

Every value in Rue has a type that determines its representation in memory and the operations that can be performed on it.

Zero-Sized Types

A zero-sized type (ZST) is a type with a size of zero bytes. Zero-sized types can be instantiated and passed by value, but they occupy no storage.

The following types are zero-sized:

• The unit type ()
• The never type !
• Empty structs (structs with no fields)
• Zero-length arrays [T; 0] for any type T

Zero-sized types have an alignment of 1 byte.

Recursive Value Types

A struct or enum MUST NOT contain itself by value, either directly or through a cycle of struct fields, enum payloads, or array elements. A non-zero by-value cycle has no finite size. A raw-pointer edge does not contain its pointee by value and therefore breaks the cycle. For uniform structural well-formedness, array edges remain recursive-type edges even when their length is zero. A recursive by-value cycle is a compile-time error (E0483).

In this section

• Integer Types
• Boolean Type
• Unit Type
• Never Type
• Array Types
• Struct Types
• String Types
• Move Semantics
• Destructors
• Mutable Strings
• Type Inference
• Floating-Point Types