• Introduction
• Lexical
• Interpolation Expression Sequence
• Grammar
• Modules
• Declarations
• Types
• Properties
• Attributes
• Pragmas
• Expressions
• Statements
• Arrays
• Associative Arrays
• Structs and Unions
• Classes
• Interfaces
• Enums
• Type Qualifiers
• Functions
• Operator Overloading
• Templates
• Template Mixins
• Contract Programming
• Conditional Compilation
• Traits
• Error Handling
• Unit Tests
• Garbage Collection
• Floating Point
• D x86 Inline Assembler
• Embedded Documentation
• Interfacing to C
• Interfacing to C++
• Interfacing to Objective-C
• Portability Guide
• Named Character Entities
• Memory Safety
• Application Binary Interface
• Vector Extensions
• Better C
• ImportC
• Live Functions
• Windows Programming
• Glossary
• Legacy Code
• Editions

Editions

Editions provide a way to evolve D by obsoletingfeatures while maintaining compatibility with code that uses thosefeatures. Editions are a module level feature, i.e. various sectionsof a module cannot be set to different editions.

The edition is set either by default, by putting it in theModuleDeclaration,or with the-edition command line switch.

Editions are meant to be backwards and forwards compatible; it makes it possible for a Dmodule targeting one edition to import a D module targeting any other edition.A template must obey the rules of the edition targeted by the module in which itis defined, not the module in which it is instantiated. Compatibility is at thesource code level; no promises of ABI compatibility are made. All code, old andnew, must be compiled with the same version of the compiler. Only one versionof DRuntime, which must support all existing editions, is to be provided with a compiler release.

Grammar

Edition:DecimalInteger

What can editions do?

• Deleting existing features -This would be the easiest change that could be made in an edition,since it would forbid future code from using deprecated features.Aside from maintaining the compiler for those features, there would be no impact.
• Adding new features -Editions are not necessary for adding new features that are purely additive,i.e., that do not interact with existing features. Editions may backportthem to previous editions where possible.
• Changing defaults -Defaults matter because they encourage and influence behavior. Newer editionscould change defaults such as@system /@safe and others.
• Changing semantics -An edition could make it so that:

  sharedint i;i += 5;

  would be lowered to:

  sharedint i;i.atomicOp!"+="(5);

Specifying the Edition

An edition level is determined by:

1. an explicit 4 digit number corresponding to the year in which the desired edition was released
2. if no edition is specified, and there is noModuleDeclaration in the source code,the edition used is theBaseline Edition, which corresponds to 2023.
3. if no edition is specified, and there is aModuleDeclaration in the source code,the edition used is the year the compiler was released.