octal escapes are not handled correctly in string literal types

[ajafff]

TypeScript Version: 2.9.0-rc

Search Terms: type octal

Code

const a: '\1' = '1'; // 'a' is of type '1' and contains '1'
const b: '\1' = '\1'; // 'b' is of type '1', but contains '\u0001'
const c = '\1'; // same as 'b'

Expected behavior:

Octal escapes in string literals are handled correctly.

For LiteralTypeNodes I would probably prefer a grammar error, but type inference also needs to handle octal escapes.

Actual behavior:

Octal escapes are ignored when converting a StringLiteral to a LiteralType.

Playground Link: https://agentcooper.github.io/typescript-play/?target=5#code/MYewdgzgLgBAhgLhgcgDoEZkwLwswbhgHoiU4sBLCGEAMxigE8AHAUzyzjABMZQwocCpA4AoftBgAjJGkw4UGZIRIoplanQYt2yTABppAV1j9Bw6miMAGW5nHhJwBXOXFSEOAFt2cS+qA

Related Issues:

[ajafff]

It seems like this is not specific to literal types. This is caused by incorrect parsing of octal escape sequences in every StringLiteral.

[DanielRosenwasser]

Duplicate of #396.

[ajafff]

#396 is about making octal escape sequences an error. Only #396 (comment) mentions some difficulties with the scanner / parser.

However, I'm ok with closing this as duplicate. I hope nobody uses octal escape sequences anymore so the type checking inconsistencies are not a problem in real world code.

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.