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Generic is "any-like" for relational operators #58938
Description
🔎 Search Terms
generics templates comparison compare less-than more-than unknown unsound function inline
🕗 Version & Regression Information
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about relational operators and comparisons
⏯ Playground Link
💻 Code
const cmp = <T,>(x: T, y: T) => x < y
null < null
cmp(null, null)
undefined < undefined
cmp(undefined, undefined)
Symbol() < Symbol()
cmp(Symbol(), Symbol())🙁 Actual behavior
Error messages:
- "The value 'null' cannot be used here.(18050)"
- "The value 'undefined' cannot be used here.(18050)"
- "The '<' operator cannot be applied to type 'symbol'.(2469)"
The errors show up for both operands of the relational operator except symbols, which only error on LHS.
The arrow fn cmp doesn't trigger any errors, even at call sites
🙂 Expected behavior
cmp should trigger an error on definition, because even though both params are same-type, they can't always be compared (symbols throw at runtime)
Additional information about the issue
No response
Activity
[-]generic is "`any`-like" for relational operators[/-][+]Generic is "`any`-like" for relational operators[/+]fatcerberus commentedon Jun 20, 2024
Technically both parameters aren't even guaranteed to be the same type, because
Tmight be a union.RyanCavanaugh commentedon Jun 21, 2024
See #52807; this is a rather breaky change to make and we're evaluating what the right course of action is. There are a lot of unconstrained (or insufficiently constrained) type parameters out there
Rudxain commentedon Jun 22, 2024
Should I close this issue (as dupe) and open one about the weird single-sidedness of
symbols? Or should I keep it as-is?typescript-bot commentedon Jun 25, 2024
This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.