TypeScript <= 5.0.4: "Hexadecimal digit expected." and "'f' is declared but its value is never read." for tagged template with escaped CRLF sequences

[na7ure-a]

🔎 Search Terms

"Hexadecimal digit expected."
"Hexadecimal digit expected TypeScript 5.0.4"
"tagged template Hexadecimal digit expected"
"f is declared but its value is never read tagged template"
"Interrupted CRLF \x0D \x0A TypeScript"
site:github.com/microsoft/TypeScript "Hexadecimal digit expected"

🕗 Version & Regression Information

This changed between versions 5.0.4 and the next release (the error is present in 5.0.4 and earlier, and absent in versions after 5.0.4 based on my testing).

⏯ Playground Link

https://www.typescriptlang.org/zh/play/?target=2&ts=5.0.4#code/GYVwdgxgLglg9mABMRAKRA6LzEC5ECGYAnogNqIC6iAlIgN4BQAvoygAaIA6AHogAyIAIogAk9RACIAkmCgBTAE6KQABwUATRAGEASgBkAYpMTNufQQEFEnANyMgA

💻 Code

function f ( ... f : any [ ] ) {
}
f ` \x 0 D ${ "Interrupted CRLF" } \x 0 A ` ;

🙁 Actual behavior

On TypeScript 5.0.4 (and earlier) tsc reports:
"Hexadecimal digit expected."
"'f' is declared but its value is never read."
On versions after 5.0.4 the errors disappear (based on my tests), indicating this was fixed in a later release.

🙂 Expected behavior

The code should compile without the "Hexadecimal digit expected." error.

Additional information about the issue

No response

[MartinJohns]

I'm confused. You say you expect this to work, and you say that it works on the current version already. So what's the bug? It's fixed already.

[RyanCavanaugh]

We only backport extremely critical fixes to prior versions, so it's expected that older versions will have bugs that newer versions don't.

[na7ure-a]

I'm confused. You say you expect this to work, and you say that it works on the current version already. So what's the bug? It's fixed already.我很困惑。你说你期望这能工作，你说它在当前版本已经可以工作了。那么问题出在哪里？它已经被修复了。

Thank you for the clarification. I’m using differences between compiler versions as a test oracle, so I originally thought issues that appear only in older releases but are fixed in later ones should be reported. For future reports, could you clarify the project’s guidance?Specifically: should I open issues for bugs that occur in a contiguous range of older versions (for example, 4.6–4.8) but are absent in both earlier and later releases, or should I only report regressions that are present in the current release? Thanks for the guidance.

[RyanCavanaugh]

You should assume the current version is the correct behavior unless you've explicitly proven otherwise through manual analysis.