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Object spread operation typings are divorced from resultant runtime values. #50185
Closed as not planned
Description
Bug Report
🔎 Search Terms
spread object
🕗 Version & Regression Information
v4.7.4 v4.8.0-beta
- This is a crash
- This changed between versions ______ and _______
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
- I was unable to test this on prior versions because _______
⏯ Playground Link
Playground link with relevant code
💻 Code
const
object1
={
hello:"World"
} as const;
const
object2
={
hello:"Mars"
} as const;
function Spread<A extends object, B extends object>(a:A,b:B){
return{
...a,
...b,
}
}
const
SSSS
=Spread(object1,object2);
// this yelds never.
// What the typesystem thinks
// Spread<A,B> => A&B
// What runtime/reality evaluates to:
// Spread<A,B> => Omit<A, keyof B>&B🙁 Actual behavior
The resultant type of the spread operation did not model that which is happening in runtime.
🙂 Expected behavior
The type system is grounded and models that which is happening in runtime.
Activity
jasa-blad commentedon Aug 4, 2022
Its hard to implement infered types when the type system gets in the way, regardless of the robustness of being able to declare type dependencies in consuming functions or classes.
RyanCavanaugh commentedon Aug 4, 2022
Duplicate #10727. Lacking a specific type operator to represent spread,
...uses intersection as the next-closest thing when one of the operands is a type parameter.