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Cannot define a matching template literal type to a defined template literal #43143
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- changed the title
[-]Cannot define a matching template literal type to a template literal in a function declaration[/-][+]Cannot define a matching template literal type to a defined template literal [/+]on Mar 8, 2021 It appears to happen in any case where there's a literal type, even the most trivial case fails:
const aString: `a${string}` = `a${'string'}`;
as constshouldn't be needed hereWe currently only produce template literal types from template literal expressions in
as constcontexts. We tried template literal types for all template literal expressions in #41891, but reverted it because it was too breaky. However, a happy medium would be to give template literal types to expressions that are contextually typed by string-like types. I can't imagine that breaking anything and it would solve this and other related issues.- locked as resolved and limited conversation to collaborators
on Oct 21, 2025
Bug Report
🔎 Search Terms
string, template, literal, type
🕗 Version & Regression Information
This is the behavior in every version I tried, including Nightly
⏯ Playground Link
Playground link with relevant code
💻 Code
🙁 Actual behavior
TS infers the type
stringfor the returned string, instead of the templated type.🙂 Expected behavior
No error!