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\u in String.rawΒ #42887
Description
Activity
Wenlu Wang (@Kingwl) you might be interested in this one.
Itβs not just
String.raw, this applies to all tagged template literals, whereΒ theΒ topβlevelTemplateStringArraycontainsΒundefinedforΒ anΒ unknownΒ escape, soΒ thisΒ should alsoΒ updateTemplateStringsArray:const taggedTemplate = (template: TemplateStringsArray, ...substitutions: unknown[]) => { console.log(template, substitutions); } // Logs: // [ // undefined, "bar", undefined, // raw: [ "foo\\uvar", "bar", "baz\\u" ] // ] // [ 123, 456 ] taggedTemplate`foo\uvar${123}bar${456}baz\u`;
Also, this doesnβt occur when theΒ
\uΒ follows aΒ substitution.Itβs not just String.raw, this applies to all tagged template literals
Sorry I'm not 100% sure what your means.
But seems the runtime behavior is as expected.
The current problem is falsely alarm.
Here's some context:
- add support for Lift Template Literal RestrictionΒ #23801
- https://tc39.github.io/proposal-template-literal-revision/
And I have found an PR who try to fix a part of the alarm: #41030
TheΒ definition ofΒ
TemplateStringArrayshouldΒ includeundefinedinΒ theΒ topβlevel indexΒ signature, whichΒ should beΒ fixed alongsideΒ this toΒ correctlyΒ describe theΒ runtimeΒ behaviour asΒ ofΒ tc39/ecma262@138c9ef.Ahhhh Okay. Got the point. Thanks.
I think that dealing with octal escapes in all strings #396 should be done before dealing with tagged templates as an exception...
π Hi, I'm the Repro bot. I can help narrow down and track compiler bugs across releases! This comment reflects the current state of this repro running against the nightly TypeScript.
Comment by ExE Boss (@ExE-Boss)
β Failed: -
Hexadecimal digit expected.
Historical Information
Version Reproduction Outputs 4.2.2, 4.3.2, 4.4.2, 4.5.2, 4.6.2 β Failed: -
Hexadecimal digit expected.
Hi, is this issue being worked on? I would like to look into this as a first issue.
The definition of TemplateStringArray should include undefined in the topβlevel index signature,
I'm afraid such a change will break existing code.
undefinedis there only if a part of string template contains invalid escape characters, and this information is available in compile-time. I'd suggest replacingTemplateStringsArraywith areadonlytuple ofstrings andundefineds, intersected with{raw: ...}. of equal-sized tuple ofstrings. This type should be backwards compatible.- locked as resolved and limited conversation to collaborators
on Oct 21, 2025
Bug Report
π Search Terms
String.raw
π Version & Regression Information
β― Playground Link
Playground link with relevant code
π» Code
π Actual behavior
Error reported:
error TS1125: Hexadecimal digit expected.π Expected behavior
Complete transpile