While reading go specification "Assignability" section, I tried to execute a couple of examples to get a better understanding of the topic, and now I can't get what am I doing wrong in my code.
According to the specification,
One of the cases when a value x is assignable to a variable of type T is as follows:
x's type V and T have identical underlying types and at least one of V or T is not a defined type.
Defined type specification states that
Type definition creates a new, distinct type with the same underlying type and operations as the given type, and binds an identifier to it.
But when I try to run following code, the build fails:
func main() {
type Defined int32
var d Defined
var i int32
d = i
}
The output is:
cannot use i (type int32) as type Defined in assignment
Meanwhile, the similar example with composite literal works fine:
func main() {
type MyMap map[string]int
var x MyMap
var y map[string]int
x = y
}
Also from the spec:
https://golang.org/ref/spec#Numeric_types
To avoid portability issues all numeric types are defined types and thus distinct