[−][src]Module abi_stable::type_layout::tagging

Tag is a dynamically typed data structure used to encode extra properties about a type in its layout constant.

Comparison semantics

Tags don't use strict equality when doing layout checking , here is an exhaustive list on what is considered compatible for each variant in the interface:

Null: A Tag which is compatible with any other one. Note that Nulls are stripped from arrays,set,and map keys.
Integers/bools/strings: They must be strictly equal.
Arrays: They must have the same length, and have elements that compare equal.
Sets/Maps: The set/map in the interface must be a subset of the implementation,

Examples

Declaring a unit type with a tag.


use abi_stable::{tag,StableAbi};

#[repr(C)]
#[derive(StableAbi)]
#[sabi( tag = r##" tag!("WAT") "## )]
struct UnitType;

Emulating const generics for strings

This emulates a const NAME:&'static str parameter, which is checked as being the same between the interface and implementation.

Structs

CheckableTag	A tag that can be checked for compatibility with another tag.
FromLiteral	Used to convert many types to `Tag`.
KeyValue	A key-value pair,used when constructing a map.
Tag	Tag is a dynamically typed data structure used to encode extra properties about a type in its layout constant.
TagErrors	The error produced when checking `CheckableTag`s.

Enums

CTVariant	The possible variants of CheckableTag.
Primitive	The primitive types of a variant,which do not contain other nested tags.
TagVariant	All the Tag variants.