0098-didset-capitalization.md

Lowercase didSet and willSet for more consistent keyword casing

• Proposal: SE-0098
• Author: Erica Sadun
• Review Manager: Chris Lattner
• Status: Rejected
• Decision Notes: Rationale

Introduction

This proposal adopts consistent conjoined keyword lowercasing.

Swift-evolution thread: RFC: didset and willset

Motivation

Swift is an opinionated language. One opinion it adheres to is that keywords should use conjoined lowercasing. Conjoined lowercase terms already in the language include typealias, associatedtype, and fallthrough. Using this casing style enables programmers to treat keywords as atomic concepts. This proposal formalizes this rule and fixes current inconsistencies.

Detailed Design

Upon adoption, Swift will rename didSet and willSet to didset and willset. Future expansions to the language will follow this adopted rule, for example didchange.

This proposal deliberately omits the dynamicType keyword, which will be addressed under separate cover: to be moved to the standard library as a standalone global function.

Impact on Existing Code

This proposal requires migration support to rename keywords that use the old convention to adopt the new convention. This is a simple substitution that should limit effect on code.

Alternatives Considered

Not adopting this rule for Swift.