Re: [Haskell-cafe] Cannot update a field in a record with a polymorphic type.

Thank you all kind folks who responded. I think a leap of reasoning has occurred and I would like to ask you all to slow down and notice it. Record update is special syntax. It is not a function. It is not as general as a function. It is not perceived nor written as a function. Ain't no lambda in it. You may say that it desugars to a function. But as a user of the language, I am unconcerned: desugar another way then! Surely a function of type `C α ⇒ Y α → Y String` may assign different strings to `y`, by consulting methods of `C`. But a record update cannot! Neither the value `y₀` nor the type variable α are ever in the scope of the update expression.