---
title: "SE-0096: Converting `dynamicType` from a property to an operator"
framework: swift-evolution
role: article
path: swift-evolution/0096-dynamictype
---

# SE-0096: Converting `dynamicType` from a property to an operator

* Proposal: [SE-0096](0096-dynamictype.md)
* Author: [Erica Sadun](https://github.com/erica)
* Review Manager: [Chris Lattner](https://github.com/lattner)
* Status: **Implemented (Swift 3.0)**
* Decision Notes: [Rationale](https://forums.swift.org/t/accepted-with-revision-se-0098-converting-dynamictype-from-a-property-to-an-operator/2853)
* Bug: [SR-2218](https://bugs.swift.org/browse/SR-2218)

## Introduction

This proposal establishes `dynamicType` as a named operator rather than a property.

Swift-evolution thread: [RFC: didset and willset](https://forums.swift.org/t/rfc-didset-and-willset/2669)

## Motivation

In Swift, `dynamicType` is a property. Because of that, it shows up as an "appropriate"  code completion for all values regardless of whether it makes sense to do so  or not. For example, Swift offers `4.dynamicType` and `myFunction().dynamicType`, etc.

Unlike most properties, it does not express a logical attribute of a specific type. Instead, it can be applied to any expression. Since `dynamicType` behaves more like a  operator (like `sizeof`), its user-facing calling syntax should follow suit.

## Detailed Design

Upon adoption of this proposal, Swift resyntaxes `dynamicType` as an operator instead of a member. This proposal puts forth `dynamicType`:

``` dynamicType(value) // returns the dynamicType of value ```

Once the Swift language has sufficient capabilities, the goal is to migrate this operation to the standard library. At this time, this operation cannot be written as a stdlib feature and it will be implemented as a compiler feature.

## Impact on Existing Code

Adopting this proposal will break code and require migration support. The postfix property syntax must change to an operator call.

## Alternatives Considered

The core team may also consider `typeof(x)` instead of `dynamicType(x)` as the call is syntactically closer to `sizeof(x)`.  Note that this may introduce confusion. Unlike Swift, identically-named C++ and C# terms return static types.  Javascript also includes `typeof(x)` but Javascript does not support static types.

## Acknowledgements

Thank you, Nate Cook