What Does the Tilde (~) Mean in Go Type Constraints

In Go type constraints, the tilde (~) means "any type that implements the specified interface or matches the underlying type."

// Accepts any type whose underlying type is int
type MyInt interface { ~int }

// Accepts int and any named type defined as int (e.g., type Age int)
type Integer interface { ~int | ~int8 | ~int16 | ~int32 | ~int64 }

The ~ operator allows generic functions to accept types based on their underlying representation rather than requiring an exact type match.

The tilde acts like a wildcard for types. Instead of requiring a specific type like int, it accepts any type that is built on top of int, such as int8 or int16. It's like saying "I accept any coin made of gold" rather than "I only accept this specific gold coin."