# Add version scheme for Swift language

## Background

The list of languages in Section 3.1, Tsble 3.1, and at
[languages-v6.html](https://dwarfstd.org/languages-v6.html), does not
list a version scheme for the Swift language. This proposal adds one.

## Overview

The Swift programming language does not have a version scheme defined
for DW_AT_language_version. This proposal defines it to use the `VVMM`
version scheme. This way "Swift 5.10" would be

    DW_AT_language(DW_LANG_Swift)
    DW_AT_language_version(510)

and "Swift 6" would be `DW_AT_language_version(600)`.

Even though Swift package releases usually have a Major.Minor.Patch
version scheme (e.g., Swift 5.9.2), the Swift compiler frontend's
LangOptions data structure only uses Major.Minor to distinguish syntax
changes in the parser (see References). This version scheme is designed
to match what the compiler does.

## Proposed Changes

Augment the table of language encodings to say

    Swift    DW_LNAME_Swift    0x001a    0    VVMM

## References

- Issue [210419.1](210419.1.html)
- [Swift downloads](https://www.swift.org/download/) (see older releases for a history of versions).
- [LangOptions.h](https://github.com/apple/swift/blob/3d32f5fc8a9087add424a2704ef1dcd89c9307ff/include/swift/Basic/LangOptions.h#L174)

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2024-04-29: Accepted.