Tslint: Rule array-type does not play well with TS 3.4.1 readonly keyword

Created on 8 Apr 2019 · 3Comments · Source: palantir/tslint

Bug Report

__TSLint version__: 5.15
__TypeScript version__: 3.4.1
__Running TSLint via__: VSCode

TypeScript code being linted

// old (pre TS 3.4.0)
type Matrix<T> = ReadonlyArray<ReadonlyArray<T>>;
// new (TS 3.4.0)
type Matrix<T> = readonly (readonly T[])[];
// code snippet

with tslint.yaml configuration:

extends:
- tslint:recommended

which uses rule array-type with option array-simple.

TSLint fails to lint second line, but TypeScript enforces usage of "readonly" before simple array types. The following line would not pass TSC:

type Matrix<T> = readonly Array<readonly T[]>;

Actual behavior

TSLint fails to lint second line.

Expected behavior

TSLint lets pass the syntax as this is the only way to make complex array types read-only (without adding an intermetiate typedef for inner elements).

P2 Bug 🌹 R.I.P. 🌹

Source

danielrentz

👍3

Most helpful comment

BTW even simpler example

type T1 = ReadonlyArray<number | string>;
type T2 = readonly (number | string)[]; // TSLint fails

danielrentz on 8 Apr 2019

👍2

All 3 comments

BTW even simpler example

type T1 = ReadonlyArray<number | string>;
type T2 = readonly (number | string)[]; // TSLint fails

danielrentz on 8 Apr 2019

👍2

💀 _It's time!_ 💀

TSLint is deprecated and no longer accepting pull requests other than security fixes. See #4534. ☠️
We recommend you instead use typescript-eslint to lint your TypeScript code with ESLint. ✅

👋 It was a pleasure open sourcing with you!