The static type (or just type) of a variable is the type given in its declaration, the type provided in the new call or composite literal, or the type of an element of a structured variable.
And here we are at one of the core features of Go, it’s static type system.
Each variable has a specific static type, which is typically provided in the variable definition, although there are a few cases where the type can be inferred.
Let’s look at some explicit examples:
var x int // x is of type `int`, and is is initialized to the zero value for int
var y int = 123 // y is of type `int`, and initialized to the value 123
var z = int(123) // Alternative form of previous line
And a few examples of inferred types:
type Person struct {
ID int
Name string
}
var p = Person{ID: 123, Name: "Bob"} // p is of type Person, the type of the
// composite literal
var name = p.Name // name is of type string, inferred from the referenced
// structured element, Person.Name
A couple of other examples, not directly called out in this part of the spec, where the type can be inferred:
func foo() int { return 3 }
var x = foo() // x is of type int, as that is the type returned by foo()
const x = 123
y = x // y is of type `int`, the default type of an integer constant literal.
Quotes from The Go Programming Language Specification, Version of January 19, 2023
