TypeScript 5.2 Iteration Plan

This document outlines our focused tasks for TypeScript 5.2. It minimally indicates intent to investigate tasks or contribute to an implementation. Nothing is set in stone, but we will strive to complete these tasks in a reasonable timeframe.

Date	Event
2023-05-30	TypeScript 5.1 Release
2023-06-23	Create 5.2 Beta (5.2.0) Build for Testing
2023-06-27	TypeScript 5.2 Beta Release
2023-08-04	Create 5.2 RC (5.2.1) Build for Testing
2023-08-08	TypeScript 5.2 RC Release
2023-08-18	Create 5.2 Final (5.2.2) Build for Testing
2023-08-22	TypeScript 5.2 Final Release 🚀

gantt
    dateFormat  YYYY-MM-DD
    TypeScript 5.1 Stabilization Period : 2023-05-15, 2023-05-30
    TypeScript 5.2 Beta Development : 2023-05-15, 2023-06-27
    TypeScript 5.2 RC Development : 2023-06-27, 2023-08-04
    TypeScript 5.2 Stabilization Period : 2023-08-04, 2023-08-22
todayMarker stroke-width:5px,stroke:#0f0,opacity:0.5

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The previous Iteration Plan for TypeScript 5.1 is available here.

Are there any plans or discussions regarding #53656?

Also interested if you have any plans regarding #41316? Working on libraries seems impossible without it sometimes.

I've been recently hitting up against #53018 and #54029 seems to open a bunch of opportunities for reverse mapped types to receive better inference. It would be a real game changer to our main APIs. Is there anything a community member can do to help with something like this?

Is #14729 still being investigated? It got closed after #51328 got accepted for 5.1, but has since been re-opened since the PR didn't actually address most of #14729's usecases.

TypeScript Bot (@typescript-bot)

TypeScript Bot (@typescript-bot) sync release-5.2 and LKG

Daniel Rosenwasser (@DanielRosenwasser)

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to sync release-5.2 with main for you. Here's the link to my best guess at the log.

Michael (@Mike-Dax)

I've been recently hitting up against #53018 and #54029 seems to open a bunch of opportunities for reverse mapped types to receive better inference. It would be a real game changer to our main APIs. Is there anything a community member can do to help with something like this?

Michael (@Mike-Dax) my PR isn't (yet) complete - it has some rough edges that I need to figure out. I'd happily collaborate on this one with somebody, I already know what I want to do there just need to find a proper way to fit those ideas into the code and the available data structures.

Here's the link to my best guess at the log.

What the… what even kind of bot is this
Bad bot

Not explicitly mentioned above but this also lands support for Change Array By Copy methods (eg arr.toReversed(), arr.toSorted(), arr.with(index, value), etc).

Issue: #50333
PR: #51367
ECMAScript proposal: https://github.com/tc39/proposal-change-array-by-copy

FYI: #54923

TypeScript Bot (@typescript-bot)

TypeScript Bot (@typescript-bot) bump release-5.2

Daniel Rosenwasser (@DanielRosenwasser)

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to update the version number on release-5.2 to 5.2.1-rc for you. Here's the link to my best guess at the log.

How template literals as computed properties on objects are now typed as literals instead of strings seems to not be mentioned in the changelog:

const key = 'foo'

// {
//    foo: number;
//    "foo-de": string;
// }

const object = {
    [key]: 1,
    [`${key}-de`]: "2"
}

// Errors in 5.1.6 with "Property 'match' does not exist on type 'string | number'."
object['foo-de'].match(/2/)
object['foo'] + 1;

Playground Link 5.2.0-beta

vs

const key = 'foo'

// {
//    [x: string]: string | number;
//    foo: number;
// }

const object = {
    [key]: 1,
    [`${key}-de`]: "2"
}


// @ts-expect-error
object['foo-de'].match(/2/)
object['foo'] + 1;

Playground Link 5.1.6

Seems like a good change but probably worth mentioning.

If im not mistaken this was changed by #53907

Also positive change: referencing const enums in template literal types used to error under --isolatedModules but doesn't anymore:

export declare const enum OBJECT_INDICATION_TYPE {
    HIGHLIGHTED_DOT = "HIGHLIGHTED_DOT"
}
type Values<T> = {
    [K in keyof T]: T[K];
}[keyof T];
export type IndicationType = `${Values<typeof OBJECT_INDICATION_TYPE>}`;
// Fixed:                                     ^^^^^^^^^^^^^^^^^^^^^^ Cannot access ambient const enums when 'isolatedModules' is enabled.(274
export {};

Playground Link

TypeScript Bot (@typescript-bot)

TypeScript Bot (@typescript-bot) bump release-5.2

Daniel Rosenwasser (@DanielRosenwasser)

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to update the version number on release-5.2 to 5.2.2 for you. Here's the link to my best guess at the log.

Version 5.2.2 is already available on npm, but I don't see a corresponding tag and release/changelog in this repository. Can you add the actual release here on the github?

It's tagged now - but can I ask what you all use the tag for?

It's tagged now - but can I ask what you all use the tag for?

Speaking for myself: Github watch notifications on release tags to know when new releases happen.

It's tagged now - but can I ask what you all use the tag for?

— Release notifications / changelogs
— Easy way to compare releases

Tim (@timbuckley)

Not explicitly mentioned above but this also lands support for Change Array By Copy methods (eg arr.toReversed(), arr.toSorted(), arr.with(index, value), etc).

Issue: #50333 PR: #51367 ECMAScript proposal: https://github.com/tc39/proposal-change-array-by-copy

I've upgraded to 5.2.2 but still shows error.
Property 'toSpliced' does not exist on type 'string[]'. Did you mean 'splice'?
Am i missing something? Tim (@timbuckley)

Tim (@timbuckley)

Not explicitly mentioned above but this also lands support for Change Array By Copy methods (eg arr.toReversed(), arr.toSorted(), arr.with(index, value), etc).
Issue: #50333 PR: #51367 ECMAScript proposal: https://github.com/tc39/proposal-change-array-by-copy

I've upgraded to 5.2.2 but still shows error. Property 'toSpliced' does not exist on type 'string[]'. Did you mean 'splice'? Am i missing something? Tim (@timbuckley)

Kowshik Achar (@RHOOPH) I think your runtime (whether browser or Node) still needs to use toSpliced, independent of whether TypeScript understands that type (which it only does after 5.2).

Node v20 is the first Node version to support it, for example. Scroll down to that line in this compatibility chart: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#browser_compatibility

target should set to esnext. In tsconfig.json

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TypeScript 5.2 Iteration Plan #54298

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DanielRosenwasser commented on May 18, 2023

fleddri commented on May 23, 2023

TmLev commented on Jun 2, 2023

Mike-Dax commented on Jun 15, 2023

max-kamps commented on Jun 23, 2023

DanielRosenwasser commented on Jun 27, 2023

typescript-bot commented on Jun 27, 2023

Andarist commented on Jun 27, 2023

fatcerberus commented on Jul 3, 2023

timbuckley commented on Jul 6, 2023

RyanCavanaugh commented on Jul 7, 2023

DanielRosenwasser commented on Aug 7, 2023

typescript-bot commented on Aug 7, 2023

eps1lon commented on Aug 11, 2023

Andarist commented on Aug 11, 2023

eps1lon commented on Aug 14, 2023

DanielRosenwasser commented on Aug 20, 2023

typescript-bot commented on Aug 20, 2023

dimatakoy commented on Aug 25, 2023

DanielRosenwasser commented on Aug 25, 2023

timbuckley commented on Aug 25, 2023

dimatakoy commented on Aug 26, 2023

RHOOPH commented on Sep 5, 2023

timbuckley commented on Sep 5, 2023

sacru2red commented on Oct 5, 2023

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