Re: [Haskell-cafe] type inference and named fields

Christian Maeder writes:

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voidcast v@(VariantWithOne{}) = v { field1 = Void , field2 = Void }

Setting field2 only assures type correctness, but the value of field2 would be ignored at runtime.

Exactly what I was proposing.

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I could write a single expression that updated all possible variants of a type, simply by unioning all their possible labels.

I want to detect errors as early as possible.

But you can already write this:

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voidcast v@(VariantWithOne{}) = v { field1 = Void , field2 = Void }

and you do not get a compile time error - it is a runtime error. I am proposing that it should not be thought of as an error at all. Regards, Malcolm