Common Generics Gotchas and Limitations in Go

Type System
2026-04-17T12:05:42+00:00
Go generics require explicit type constraints and careful slice handling to avoid type errors and memory leaks.

Go generics have specific limitations regarding type constraints, interface satisfaction, and memory management that can cause unexpected behavior. The most common issues include the inability to use any for type assertions without explicit constraints, the requirement for comparable constraints in map keys, and potential memory leaks in slice operations if the underlying array is not cleared. Use explicit type parameters and constraints to define behavior, and always assign the return value of slice-modifying functions like slices.Delete to avoid retaining references to deleted elements.

// Correct usage of generics with explicit constraints
func Sum[T int | float64](s []T) T {
    var total T
    for _, v := range s {
        total += v
    }
    return total
}

// Avoid memory leaks by assigning the result of slice modifications
s := []string{"a", "b", "c"}
s = slices.Delete(s, 1, 2) // Must assign result to 's'