for rust, it counts as a 'feature' because it provides safety guarantee, and they're opt-in (can use unsafe)

as for haskell, that immutability also provides guarantee of 'referential-transparency', which the users/libraries can use to their advantange.

But in python's case, you have to define the multi-line function *outside* the chaining, and 'forcing to name things' isn't always good (especially for constantly-changing code)

def hideEmail(user): return { ...user, email: user.hideEmail? '': user.email, }

users.map(hideEmail)

// later: def hideEmailAndPhone(user): return { ...user, email: user.hideEmail? '': user.email, phoneNo: ... // same stuff }

users.map(hideEmailAndPhone) ---

As for JS/TS, you can have 'named-callback-fn':

users.map(function hidePrivateFields(user) { ... })

and it's not difficult to come up with 'named-lambda-fn' standard

users.map(hidePrivateFields(user) => { ... })