Can Go Generics Enforce the Presence of Specific Fields in Structs?

Enforcing Field Presence with Generics in Go

When developing generic functions in Go, ensuring that passed values adhere to specific field criteria can be crucial. In this context, a common inquiry arises: can we utilize generics to validate the presence of certain fields, such as ID int, in passed values?

Although various approaches have been attempted, the current Go generics implementation in Go 1.18 introduces a limitation: structural types are not supported. As a result, defining a generic function that accepts only values with a specific field, without relying on interface methods, is currently infeasible.

However, it's crucial to understand the significance of the approximation syntax ~T. In the example provided, ~struct{ ID int } implies types whose underlying type is precisely struct{ ID int }. This excludes structs that possess an ID int field alongside other fields.

While a proposal for field terms in interface constraints exists, it is not included in Go 1.18. Therefore, the current generics implementation lacks the syntax to define partial struct types.

Consequently, to ensure values possess specific fields, the only viable option remains to define the corresponding methods in an interface.

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