Go 1.24 Introduces Generic Type Alias Support

Since Go 1.18 introduced generics, many developers expected a major shift, but the feature is still evolving. Go 1.24 now adds a new capability: allowing type aliases to declare their own type parameters.

Background

The original generics proposal stated that a type alias can reference a generic type, but the alias itself cannot have its own parameters because handling constrained type parameters was unclear.

Previously, declaring an alias with a generic parameter such as type A[P any] = P was illegal and resulted in a compilation error.

Go 1.24: Generic Support for Type Aliases

After years of discussion, Go 1.24 (scheduled for release in February) will permit type aliases to have type parameters.

Example usage:

// Define a generic slice type
type GenericSlice[T any] = []T

// Example: custom struct slice
type Fish struct {
    Name        string
    IsGrilled   bool
    Ingredients []string
}

func main() {
    // Generic slice of strings
    words := GenericSlice[string]{"Go", "Rocks"}
    fmt.Println("Words:", words)

    // Generic slice of Fish structs
    fishes := GenericSlice[Fish]{
        {Name: "Salmon", IsGrilled: true, Ingredients: []string{"Salt", "Lemon", "Garlic"}},
        {Name: "Tuna", IsGrilled: false, Ingredients: []string{"Soy Sauce", "Wasabi"}},
    }
    fmt.Println("Grilled Fish Menu:", fishes)
}

Running this program produces:

Words: [Go Rocks]
Grilled Fish Menu: [{Salmon true [Salt Lemon Garlic]} {Tuna false [Soy Sauce Wasabi]}]

On Go 1.23 the same code fails with the error:

./prog.go:6:6: generic type alias requires GOEXPERIMENT=aliastypeparams

This is because the feature was experimental in Go 1.23 and becomes a standard part of the language in Go 1.24.

Summary

Since generics were officially added in Go 1.18, the language has been iteratively refined. The new support for generic type aliases, a feature that took nearly four years to land, marks another step forward, though developers may still encounter rough edges.

For further reading, see the linked articles on other Go 1.24 features.