So we now know that types are either identical or different. let’s look at the details, with examples.

Type identity

… In detail:

• Two array types are identical if they have identical element types and the same array length.

So given:

type (
	X = [10]int
	Y = X
	Z [10]int
)

Types X, Y, and [10]int are identical to each other, but not to [9]int or [10]int32. Type Z is also different from all the others, due to the fact that it is a named type.

Note that X and Y are not actually named types; the equal sign (=) indicates that they are aliases to the unnamed type [10]int.

• Two slice types are identical if they have identical element types.

Given:

type(
	A0 = []string
	A1 = A0
	AZ []string
)

Types A0, A1 and []string are identical to each other, but not to []int or AZ.

• Two struct types are identical if they have the same sequence of fields, and if corresponding fields have the same names, and identical types, and identical tags. Non-exported field names from different packages are always different.

Therefore:

• struct{ Name string, Age int } is different from struct{ Age int, Name string } because the sequence of fields differs.
• struct{ Name string, Age int } is different from struct{ Fullname string, Age int } because field names differ.
• struct{ Name string, Age int } is different from struct{ Name string, Age uint } because field types differ.
• struct{ Name string `json:"name"`, Age int } is different from struct{ Name string, Age int } because struct tags differ.
• struct{ name string } defined in package foo is different from struct{ name string } defined in package bar.

And jumping out of order a bit…

• Two map types are identical if they have identical key and element types.

Given:

type (
	M1 = map[string]any
	M2 = map[string]string
)

M1 and M2 are different. The empty interface is a distinct type, and does not act as a wildcard in compound types such as maps.

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