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GeezerVison is showing github.com — Improved support for read-only arrays and tuples by ahejlsberg · Pull Request #29435 · microsoft/TypeScript

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@ahejlsberg

@ahejlsberg Anders Hejlsberg (ahejlsberg) commented Jan 15, 2019 •
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This PR improves our support for read-only arrays and tuples:

  • readonly modifier on array types: readonly T[] corresponds to ReadonlyArray<T> (similar to how T[] corresponds to Array<T>).
  • readonly modifier on tuple types: readonly [T0, T1, ...] correponds to a tuple type that derives from ReadonlyArray<T0 | T1 | ...> and has read-only element positions.
  • Support for read-only arrays and tuples in mapped types. When a mapped type specifies a +readonly modifier, read-write array and tuple types are mapped to their read-only form, and when a mapped type specifies a -readonly modifier, read-only array types and tuples are mapped to their read-write form. This means that Readonly<T> now produces read-only forms of arrays and tuples.

Some examples:

function f1(mt: [number, number], rt: readonly [number, number]) {
    mt[0] = 1;  // Ok
    rt[0] = 1;  // Error, read-only element
}

function f2(ma: string[], ra: readonly string[], mt: [string, string], rt: readonly [string, string]) {
    ma = ra;  // Error
    ma = mt;  // Ok
    ma = rt;  // Error
    ra = ma;  // Ok
    ra = mt;  // Ok
    ra = rt;  // Ok
    mt = ma;  // Error
    mt = ra;  // Error
    mt = rt;  // Error
    rt = ma;  // Error
    rt = ra;  // Error
    rt = mt;  // Ok
}

type ReadWrite<T> = { -readonly [P in keyof T] : T[P] };

type T0 = Readonly<string[]>;  // readonly string[]
type T1 = Readonly<[number, number]>;  // readonly [number, number]
type T2 = Partial<Readonly<string[]>>;  // readonly (string | undefined)[]
type T3 = Readonly<Partial<string[]>>;  // readonly (string | undefined)[]
type T4 = ReadWrite<Required<T3>>;  // string[]

Fixes #26864.
Fixes #28540.
Fixes #28968.

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Anders Hejlsberg (ahejlsberg) added 6 commits January 12, 2019 08:45
@ahejlsberg
Respect readonly mapped type modifier when mapping arrays and tuples
903863a
@ahejlsberg
Support 'readonly' type modifier on array and tuple types
bb8378f
@ahejlsberg
Accept new baselines
7b00a29
@ahejlsberg
Update array/tuple relationship checking
db840f4
@ahejlsberg
Add tests
cff7874
@ahejlsberg
Accept new baselines
a7ca7f4
@ahejlsberg
Anders Hejlsberg (ahejlsberg) requested review from Daniel Rosenwasser (DanielRosenwasser) and Ryan Cavanaugh (RyanCavanaugh) January 15, 2019 23:42
j-oliveras
Jordi Oliveras Rovira (j-oliveras) reviewed Jan 16, 2019
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Comment thread src/compiler/diagnosticMessages.json Outdated
"category": "Error",
"code": 1353
},
"'readonly' type modifier is only permitted on array and typle types.": {

@j-oliveras Jordi Oliveras Rovira (j-oliveras) Jan 16, 2019

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Typo: typle to tuple.

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@ahejlsberg Anders Hejlsberg (ahejlsberg) Jan 16, 2019

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Jordi Oliveras Rovira (@j-oliveras) Oops. Thanks!

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@Igorbek Igor Oleinikov (Igorbek) mentioned this pull request Jan 16, 2019
Covariance / Contravariance Annotations #1394
Closed
sheetalkamat
Sheetal Nandi (sheetalkamat) reviewed Jan 16, 2019
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Comment thread src/compiler/checker.ts Outdated
}
else if (node.operator === SyntaxKind.ReadonlyKeyword) {
if (node.type.kind !== SyntaxKind.ArrayType && node.type.kind !== SyntaxKind.TupleType) {
return grammarErrorOnFirstToken(node, Diagnostics.readonly_type_modifier_is_only_permitted_on_array_and_typle_types, tokenToString(SyntaxKind.SymbolKeyword));

@sheetalkamat Sheetal Nandi (sheetalkamat) Jan 16, 2019

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Add test for this?

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Anders Hejlsberg (ahejlsberg) added 3 commits January 16, 2019 09:46
@ahejlsberg
Fix typo
2256f91
@ahejlsberg
Add more tests
2ccc106
@ahejlsberg
Accept new baselines
b611a51
sheetalkamat
Sheetal Nandi (sheetalkamat) reviewed Jan 16, 2019
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Comment thread src/compiler/parser.ts
switch (operator) {
case SyntaxKind.KeyOfKeyword:
case SyntaxKind.UniqueKeyword:
case SyntaxKind.ReadonlyKeyword:

@sheetalkamat Sheetal Nandi (sheetalkamat) Jan 16, 2019

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Think we need test/handling for .d.ts generation and decorator for this new typeNode kind.

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Anders Hejlsberg (ahejlsberg) added 2 commits January 16, 2019 12:45
@ahejlsberg
Add .d.ts generation test
0eac506
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Accept new baselines
d24a63d
@dead-claudia Claudia Meadows (dead-claudia) mentioned this pull request Jan 16, 2019
Add a mutating return type operator to indicate whether a function modifies a property indirectly #29346
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5 tasks done
@Jessidhia

Jessica Franco (Jessidhia) commented Jan 17, 2019

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Does this improved support for readonly arrays mean it's now possible to have readonly array/tuples as the type of a rest argument?

function f(...args: ReadonlyArray<string>) {} is currently a type error.
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@ahejlsberg

Anders Hejlsberg (ahejlsberg) commented Jan 17, 2019

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@Kovensky Isn't in the PR currently, but I see no reason why we couldn't support it. I will fix it, it's just a minor change.
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Anders Hejlsberg (ahejlsberg) added 3 commits January 17, 2019 06:06
@ahejlsberg
Allow rest parameter type to be a readonly array or tuple
e581649
@ahejlsberg
Add tests
2200d35
@ahejlsberg
Accept new baselines
ef89d26
Sheetal Nandi (sheetalkamat) added a commit to microsoft/TypeScript-TmLanguage that referenced this pull request Jan 18, 2019
@sheetalkamat
Readonly modifier support from PR microsoft/TypeScript#29435
76cfeab
@ahejlsberg Anders Hejlsberg (ahejlsberg) mentioned this pull request Jan 21, 2019
Const contexts for literal expressions #29510
Merged
@DanielRosenwasser Daniel Rosenwasser (DanielRosenwasser) mentioned this pull request Jan 24, 2019
Design Meeting Notes, 1/18/2019 #29568
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RyanCavanaugh
Ryan Cavanaugh (RyanCavanaugh) requested changes Jan 25, 2019
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+1 for .d.ts emit coverage - the only .d.ts currently in this set has semantic errors in its originating file, which makes it shaky at best

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@RyanCavanaugh Ryan Cavanaugh (RyanCavanaugh) assigned Anders Hejlsberg (ahejlsberg) Jan 25, 2019
@sheetalkamat

Sheetal Nandi (sheetalkamat) commented Jan 25, 2019

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I think having decorator test is good idea too.. since we normally forget that when we enable new kind of type annotation.
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@RyanCavanaugh

Ryan Cavanaugh (RyanCavanaugh) commented Jan 25, 2019

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// @emitDecoratorMetadata: true
// @experimentalDecorators: true
// @declaration: true

declare const someDec: any;
class A {
  @someDec
  j: readonly string[];
  @someDec
  k: readonly [string, number];
}
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@ahejlsberg
Anders Hejlsberg (ahejlsberg) deleted the readonlyArrayTuple branch January 30, 2019 23:59
@zhuravlikjb

Anton Lobov (zhuravlikjb) commented Jan 31, 2019

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Is this an intended change that a single 'readonly' is no longer parsed as a type?
Such code compiled fine before this change:

type readonly = string;
var q: readonly;

(This is not a sample from real code, just a test case.)

Seems that it is not a serious issue, but would be nice to know if this was planned, as you still may declare a type named 'readonly' but cannot use it anymore.
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@ahejlsberg

Anders Hejlsberg (ahejlsberg) commented Jan 31, 2019

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Anton Lobov (@zhuravlikjb) No, that was not intended. I will look at getting it fixed.
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@Flarna Gerhard Stöbich (Flarna) mentioned this pull request Jan 31, 2019
[node] correct SlowBuffer DefinitelyTyped/DefinitelyTyped#32661
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@ajafff

Klaus Meinhardt (ajafff) commented Feb 4, 2019

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Using a version of TypeScript that contains this PR creates declaration files which are not compatible with older versions of TypeScript.

In case someone else has the same problem: I created a transformer to downlevel readonly array types in declaration files: https://github.com/ajafff/ts-transform-readonly-array
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@falsandtru

falsandtru (falsandtru) commented Feb 4, 2019

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Anders Hejlsberg (@ahejlsberg) This feature leaved some large bugs (Maybe regression). Please fix them: #29442 #29702
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@ahejlsberg

Anders Hejlsberg (ahejlsberg) commented Feb 5, 2019

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falsandtru (@falsandtru) Those issues are not related to this PR, but I have a fix in #29740.
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@mohsen1 Mohsen Azimi (mohsen1) mentioned this pull request Feb 5, 2019
readonly function arguments #29742
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5 tasks done
@falsandtru

falsandtru (falsandtru) commented Feb 5, 2019

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Indeed, I thought another PR. Anyway, thanks for fixing.
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@simonbuchan

Simon Buchan (simonbuchan) commented Feb 7, 2019

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I assume the extension to readonly SomeObject or readonly T is not worth the native compiler support, now that Readonly<T> can work for everything as expected? React.Ref<readonly T> such that it's assignable from Ref<U> for U extends T would be kind of neat though.
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This was referenced Feb 13, 2019
TypeScript 3.4 meta-issue babel/babel#9502
Closed
TypeScript readonly type modifier babel/babel#9503
Closed
@ikokostya ikokostya mentioned this pull request Feb 14, 2019
ReadonlyArray with rest parameters #15972
Closed
@ulrichb ulrichb mentioned this pull request Feb 24, 2019
Generic argument type inference regression in TS 3.4 #30074
Closed
@dragomirtitian Titian Cernicova-Dragomir (dragomirtitian) mentioned this pull request Mar 8, 2019
DeepReadonly type fails to compile on typescript 3.1.1+ #29566
Closed
@DanielRosenwasser Daniel Rosenwasser (DanielRosenwasser) mentioned this pull request Mar 8, 2019
TypeScript 3.4 Iteration Plan #30281
Closed
@felixfbecker

Felix Becker (felixfbecker) commented Mar 9, 2019

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Is it still possible to declare a writable property with an immutable array? For example, constructable stylesheets defines document.adoptedStyleSheets as an array that is immutable and needs to be reassigned to be changed:

element.shadowRoot.adoptedStyleSheets = [...element.shadowRoot.adoptedStyleSheets, styleSheet]
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@jberry93 Jeffrey Berry (jberry93) mentioned this pull request Mar 10, 2019
TypeScript Computed Properties jberry93/jeffreyberry.dev#4
Open
@bjchambers Ben Chambers (bjchambers) mentioned this pull request Mar 28, 2019
readonly mapped type modifiers for Map / ReadonlyMap #30633
Open
5 tasks done
@ajafff Klaus Meinhardt (ajafff) mentioned this pull request Mar 30, 2019
3.4.1 breaks backward compatibility for users of ReadonlyArray #30662
Closed
@hasparus Piotr Monwid-Olechnowicz (hasparus) mentioned this pull request Apr 1, 2019
Upgrade to TypeScript version 3.4 codesandbox/codesandbox-client#1683
Closed
@PopGoesTheWza PopGoesTheWza (PopGoesTheWza) mentioned this pull request Apr 3, 2019
TypeError: Cannot read property 'instantiations' of undefined when use as const #30664
Closed
@ibezkrovnyi Igor Bezkrovnyi (ibezkrovnyi) mentioned this pull request Apr 12, 2019
[@types/prop-types] Add support of as const to oneOf DefinitelyTyped/DefinitelyTyped#34706
Merged
@ahejlsberg Anders Hejlsberg (ahejlsberg) mentioned this pull request Jun 7, 2019
Regression in array destruction in TypeScript 3.3 #29731
Closed
@bengry Ben Grynhaus (bengry) mentioned this pull request Jun 11, 2019
Take a readonly array when possible mobxjs/mobx-state-tree#1314
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3 tasks done
@jcalz Joe Calzaretta (jcalz) mentioned this pull request Jul 15, 2019
Playground: code formmating broken with TS3.4+ readonly notation microsoft/TypeScript-Website#32
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@merlinnot Natan Sągol (merlinnot) mentioned this pull request Jul 24, 2019
error TS1005: ';' expected on tsc firebase/firebase-functions#404
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@jack-williams Jack Williams (jack-williams) mentioned this pull request Aug 13, 2019
Support readonly types with inference #32812
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5 tasks done
@sandersn Nathan Shively-Sanders (sandersn) mentioned this pull request Feb 3, 2020
Do not materialize optional undefined properties inside actual types #28727
Closed
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@sheetalkamat Sheetal Nandi (sheetalkamat) sheetalkamat left review comments
@RyanCavanaugh Ryan Cavanaugh (RyanCavanaugh) RyanCavanaugh approved these changes
@DanielRosenwasser Daniel Rosenwasser (DanielRosenwasser) Awaiting requested review from DanielRosenwasser
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@j-oliveras Jordi Oliveras Rovira (j-oliveras) j-oliveras left review comments
@rbuckton Ron Buckton (rbuckton) rbuckton left review comments
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12 participants

@ahejlsberg @Jessidhia @sheetalkamat @RyanCavanaugh @typescript-bot @zhuravlikjb @ajafff @falsandtru @simonbuchan @felixfbecker @rbuckton @j-oliveras
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