Repository navigation
Template literal type ${string}${number}${string} errors on valid values #57355
Description
🔎 Search Terms
"${string}${number}${string}", "template literal types number between strings"
🕗 Version & Regression Information
This is the behavior in every version I tried, and I reviewed the FAQ for entries about template literal types
⏯ Playground Link
💻 Code
const myString:`${string}${number}${string}` = 'test123test';
// ^^^^^^^^ Type '"test123test"' is not assignable to type '`${string}${number}${string}`'.ts(2322)
const myString2:`${string}${number}` = 'test123';
// ^^^^^^^^ Type '"test123"' is not assignable to type '`${string}${number}`'.ts(2322)
const myString3:`${number}${string}` = '123test'; // passes for some reason🙁 Actual behavior
Received error "Type '"test123test"' is not assignable to type '${string}${number}${string}'.ts(2322)" when pattern matches
🙂 Expected behavior
I expect it to match any literal string type that has a number within it
Additional information about the issue
My real use case is that I would like to be able to exclude/omit patterns like ${string}${number}${string}, but that's not possible since it doesn't match
Activity
jcalz commentedon Feb 9, 2024
See #57126 and essentially intentional as described in #40336:
So
`${string}${number}${string}`matches the first character againststring, the second againstnumber, and then the rest of the string againststring. Yes, it's weird.RyanCavanaugh commentedon Feb 9, 2024
As a general principle, template string literals aren't regexes and don't have regex capabilities. Anything that requires backtracking (or extensive lookahead) isn't going to happen.