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doc/option-types: Update sum types

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Robert Hensing 2024-04-04 11:47:36 +02:00
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nixos/doc/manual/development/option-types.section.md
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@ -307,16 +307,15 @@ If some values are instances of more than one of the types, it is not possible t
## Sum types {#sec-option-types-sums}
A sum type can be thought of, conceptually, as a *`types.enum`* where each valid item is paired with a type, through some value syntax.
A sum type can be thought of, conceptually, as a *`types.enum`* where each valid item is paired with at least a type, through some value syntax.
Nix does not have a built-in syntax for this pairing of a label and a type or value, so sum types may be represented in multiple ways.
If the built-in Nix value types provide enough distinction, you simplify your syntax with a [union type](#sec-option-types-unions) instead.
If the you're interested in can be distinguished without a label, you may simplify your value syntax with a [union type](#sec-option-types-unions) instead.
`types.attrTag` *`{ attr1 = t1; attr2 = t2; ... }`*
`types.attrTag` *`{ attr1 = option1; attr2 = option2; ... }`*
: An attribute set containing one attribute, whose name must be picked from
the attribute set (`attr1`, etc) and whose value must be of the accompanying
type.
the attribute set (`attr1`, etc) and whose value consists of definitions that are valid for the corresponding option (`option1`, etc).
This type appears in the documentation as _attribute-tagged union_.