This is not valid syntax, but is there something similar that can be done to get a new updated anonymous record, similar as using with with normal records?
type user = User {id: int, ... more fields}
let u = User {id = 1, ...}
let u2 = User with id = 2
If you're asking how you can access the entirety of the record from a constructor, you can do this with pattern-matching.
# type user = User of { id : int; name : string };;
type user = User of { id : int; name : string; }
# let u = User { id=1; name="foo" };;
val u : user = User {id = 1; name = "foo"}
# let u2 =
let User r = u in
User { r with id=2 };;
val u2 : user = User {id = 2; name = "foo"}
You can also employ as to bind a name to part of the record while binding r to the entire record.
# let u3 =
let User ({id; _} as r) = u2 in
User { r with id=id+1 };;
val u3 : user = User {id = 3; name = "foo"}
Since User {id; _} as r would bind r to the entire pattern, parentheses are needed to limit r to just the record portion of the pattern.