Define generic implementations of Struct and Typed methods. Refs #564.
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…ods. Refs Copilot-Language#564. This adds functionality for implementing the class methods of `Struct` and `Typed` using `GHC.Generics`. As such, one can now easily define instances of these classes by deriving a `Generic` instance for the struct data type, i.e., ```hs data MyStructType = ... deriving Generic instance Struct MyStructType where typeName = typeNameDefault toValues = toValuesDefault updateField = updateFieldDefault instance Typed MyStructType where typeOf = typeOfDefault ``` This work is based off of an initial implementation by Marten Wijnja (@Qqwy). Note that I do not yet change any of the default implementations of any `Struct` or `Typed` methods. This is because several `Struct` instances in the wild currently do not define implementations of `updateField`, and moreover, they also do not define `Generic` instances for the corresponding data types. As such, changing the default implementation of `updateField` to use a `Generic`-based default would cause these instances in the wild to no longer compile. We will explore changing the default implementations after a suitable transition period. Co-authored-by: Marten Wijnja <[email protected]>
…opilot-Language#564. In the future, we plan to change the default implementation for `updateField` such that it will require a `Generic` instance. This will break any existing `Struct` instance that omits an implementation of `updateField` and also does not define a `Generic` instance for the struct data type. Unfortunately, there does not appear to be a way for GHC to warn about this combination of properties, but we can at least warn about this in the `updateField` Haddocks.
…. Refs Copilot-Language#564. Using recently added `Generic`-based implementations, much of the boilerplate code needed to define `Struct` and `Typed` in the struct-related `copilot` examples can be replaced with much simpler implementations. Note that I have intentionally _not_ used `updateFieldDefault` in the `StructsUpdateField.hs` example, as that example is intended to demonstrate how one would implement `updateField` by hand. This work is based off of an initial implementation by Marten Wijnja (@Qqwy). Co-authored-by: Marten Wijnja <[email protected]>
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This adds functionality for implementing the class methods of
StructandTypedusingGHC.Genericsincopilot-core. As such, one can now easily define instances of these classes by deriving aGenericinstance for the struct data type, i.e.,This work is based off of an initial implementation by Marten Wijnja (@Qqwy).
Note that I do not yet change any of the default implementations of any
StructorTypedmethods. This is because severalStructinstances in the wild currently do not define implementations ofupdateField, and moreover, they also do not defineGenericinstances for the corresponding data types. As such, changing the default implementation ofupdateFieldto use aGeneric-based default would cause these instances in the wild to no longer compile. We will explore changing the default implementations after a suitable transition period.I have also modified the struct-related
copilotexamples to implement theirStructandTypedinstances using these new functions. Note that I have intentionally not usedupdateFieldDefaultin theStructsUpdateField.hsexample, as that example is intended to demonstrate how one would implementupdateFieldby hand.Fixes #564. Supersedes #516.