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Assignability of type parameters

June 6, 2023

Let’s finish up our discussion of assignability by looking at how type parameters are special.

Assignability

…

Additionally, if x’s type V or T are type parameters, x is assignable to a variable of type T if one of the following conditions applies:

  • x is the predeclared identifier nil, T is a type parameter, and x is assignable to each type in T’s type set.
func foo[T *int | *int32](t T) {
	t = nil
}
  • V is not a named type, T is a type parameter, and x is assignable to each type in T’s type set.
func foo[T int | int32](t T) {
	t = 234
}
  • V is a type parameter and T is not a named type, and values of each type in V’s type set are assignable to T.
func foo[V int | int32](x V) {
	var t any = x
}

Quotes from The Go Programming Language Specification Version of December 15, 2022

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