该类型别名语法是否为Go？ [关闭]

Question

I did not get the below syntax in ../go/src/net/http/server.go:

var defaultServeMux ServeMux

where

ServeMux is a struct

type ServeMux struct {
    mu    sync.RWMutex
    m    map[string]muxEntry
    es    []muxEntry
    hosts    bool
}

---

In GO, type aliasing looks like type T1 = T2.

Is the above syntax(used for defaultServeMux) anything to do with type aliasing?

Answer 1

The line you quoted is just the declaration of a variable of type ServeMux which is the alternative, explicit variant of definition by assignment. For example these two statements are equivalent:

var foo ServeMux = ServeMux{}
foo := ServeMux{}

In both cases foo has the type ServeMux.

You can read about the variable declaration syntax here. In the global variable scope the := shorthand is not allowed which is why the var syntax is used to define global variables (as is the case in your example).

Type "aliases", i.e. the declaration of new types based on existing types has a different syntax and has nothing to do with this.