**Code**: Looks like the [`readonly` modifier for arrays](https://github.com/Microsoft/TypeScript/wiki/What's-new-in-TypeScript#improvements-for-readonlyarray-and-readonly-tuples) breaks code reformatting in the Playground. ```ts // comment out to allow reformatting const oops: readonly number[] = [1, 2, 3]; /* SyntaxError: "',' expected. (2:22), parser-typescript.js > 2 | const oops: readonly number[] = [1, 2, 3]; | ^ */ // Alt + Shift + F: IT DOES NOTHING!!! const x = 1; ``` **Expected behavior:** Code reformats (so `const x = 1;` is moved to a single line) **Actual behavior:** Code does not reformat. A console error indicates that the `readonly` modifier is not expected. **Playground Link:** [Playground Link](https://www.typescriptlang.org/play/index.html#code/PTAEGMHsFtoUwHYBdSQK4qZUBDANnpAO6gBOcAZpKdDkkgJYIDmAUFAgM4qSQAOnAFxk4OACaQEeAJ6gEaaACM4pANoBdUAF5QqgIwAaUACYjAZnUBuVsABUrAMrTkOAB4BRUqWrCARAHIDf1A4Vz44cCQ4MQA6UAAKY0FjYwBKIz4cUk4VAFokaXDOcFIGPiQYgCtOVgA+E1AAHwhJblR+IRFxSRk5BWU1TR19I1NQC2tQKabp2bn52YA9VltgVhswAEE8FABqUAcACwYKPdAAMWEASQAVUAARAHl3B1AAOUebgAkrt4BxACEQPYrRQrFcoFYOlYeksQA) **Related Issues:** microsoft/TypeScript#29435, introducing the `readonly` modifier for array types