为什么这些Go类型不同？

如何解决为什么这些Go类型不同？

在下面的示例中，根据time，从GetTime()返回的time.Time类型与types.Identical()不同。为什么是这样？两种类型在打印时均为time.Time。

package main

import (
    "fmt"
    "go/ast"
    "go/importer"
    "go/parser"
    "go/token"
    "go/types"

    "golang.org/x/tools/go/packages"
)

const example = `package main

import "time"

func GetTime() time.Time {
    return time.Time{}
}

func main() {
}`

func GetTimeObject() types.Object {
    cfg := &packages.Config{
        Mode:       packages.LoadAllSyntax,}
    loadedPackages,err := packages.Load(cfg,"time")
    if err != nil {
        panic(err)
    }

    timePkg := loadedPackages[0]
    timeObject := timePkg.Types.Scope().Lookup("Time")
    return timeObject
}

func main() {
    fset := token.NewFileSet()

    f,err := parser.ParseFile(fset,"example.go",example,0)
    if err != nil {
        panic(err)
    }

    conf := types.Config{Importer: importer.Default()}
    pkg,err := conf.Check("example",fset,[]*ast.File{f},nil)
    if err != nil {
        panic(err)
    }

    getTimeObj := pkg.Scope().Lookup("GetTime")
    if getTimeObj == nil {
        panic("not found")
    }

    switch t := getTimeObj.Type().(type) {
    case *types.Signature:
        results := t.Results()
        if results.Len() != 1 {
            panic("unexpected")
        }

        retobject := results.At(0)
        timeObject := GetTimeObject()

        fmt.Printf("time type: %v\n",timeObject.Type()) // time.Time
        fmt.Printf("return type: %v\n",retobject.Type()) // time.Time
        fmt.Printf("identical: %t\n",types.Identical(timeObject.Type(),retobject.Type())) // false
    default:
        panic("unexpected")
    }
}

解决方法

它们是不同的，使用%T和%#v将代码更改为打印详细信息类型信息，您将有所不同：

        fmt.Printf("time type: %T %#v\n",timeObject,timeObject.Type())                    
        fmt.Printf("return type: %T %#v\n",retObject,retObject.Type())                    

输出：

time type: *types.TypeName &types.Named{info:0x2,obj:(*types.TypeName)(0xc0017e9a90),orig:(*types.Struct)(0xc001b22780),underlying:(*types.Struct)(0xc001b22780),methods:[]*types.Func{(*types.Func)(0xc0017e8a00),(*types.Func)(0xc0017e8a50),(*types.Func)(0xc0017e8aa0),(*types.Func)(0xc0017e9ae0),(*types.Func)(0xc0017e9b30),(*types.Func)(0xc0017e9b80),(*types.Func)(0xc0017e9bd0),(*types.Func)(0xc0017e9c20),(*types.Func)(0xc0017e9c70),(*types.Func)(0xc0017e9cc0),(*types.Func)(0xc0017e9d10),(*types.Func)(0xc0017e9d60),(*types.Func)(0xc0017e9db0),(*types.Func)(0xc0017e9e00),(*types.Func)(0xc0017e9f90),(*types.Func)(0xc00195c000),(*types.Func)(0xc00195c050),(*types.Func)(0xc00195c0a0),(*types.Func)(0xc00195c0f0),(*types.Func)(0xc00195c140),(*types.Func)(0xc00195c190),(*types.Func)(0xc00195c1e0),(*types.Func)(0xc00195c280),(*types.Func)(0xc00195c2d0),(*types.Func)(0xc00195c370),(*types.Func)(0xc00195c3c0),(*types.Func)(0xc00195c410),(*types.Func)(0xc00195c460),(*types.Func)(0xc00195c4b0),(*types.Func)(0xc00195c910),(*types.Func)(0xc00195c960),(*types.Func)(0xc00195ca50),(*types.Func)(0xc00195caa0),(*types.Func)(0xc00195cdc0),(*types.Func)(0xc00195ce10),(*types.Func)(0xc00195ce60),(*types.Func)(0xc00195ceb0),(*types.Func)(0xc00195cf00),(*types.Func)(0xc00195cf50),(*types.Func)(0xc00195cfa0),(*types.Func)(0xc00195cff0),(*types.Func)(0xc00195d040),(*types.Func)(0xc00195d090),(*types.Func)(0xc00195d0e0),(*types.Func)(0xc00195d130),(*types.Func)(0xc00195d180),(*types.Func)(0xc00195d1d0),(*types.Func)(0xc00195d220),(*types.Func)(0xc00195d3b0),(*types.Func)(0xc00195d400)}}
return type: *types.Var &types.Named{info:0x0,obj:(*types.TypeName)(0xc00005ff90),orig:types.Type(nil),underlying:(*types.Struct)(0xc000063320),methods:[]*types.Func{(*types.Func)(0xc000172ff0),(*types.Func)(0xc000173130),(*types.Func)(0xc0001732c0),(*types.Func)(0xc0001733b0),(*types.Func)(0xc0001734a0),(*types.Func)(0xc000173590),(*types.Func)(0xc000173680),(*types.Func)(0xc000173770),(*types.Func)(0xc000173810),(*types.Func)(0xc000173900),(*types.Func)(0xc0001739f0),(*types.Func)(0xc000173b30),(*types.Func)(0xc000173c70),(*types.Func)(0xc000173db0),(*types.Func)(0xc000173ea0),(*types.Func)(0xc000173f90),(*types.Func)(0xc0003e0140),(*types.Func)(0xc0003e0460),(*types.Func)(0xc0003e0550),(*types.Func)(0xc0003e0640),(*types.Func)(0xc0003e0730),(*types.Func)(0xc0003e09b0),(*types.Func)(0xc0003e0af0),(*types.Func)(0xc0003e0c80),(*types.Func)(0xc0003e0d70),(*types.Func)(0xc0003e0e60),(*types.Func)(0xc0003e0f50),(*types.Func)(0xc0003e1040),(*types.Func)(0xc0003e1130),(*types.Func)(0xc0003e1270),(*types.Func)(0xc0003e13b0),(*types.Func)(0xc0003e1590),(*types.Func)(0xc0003e17c0),(*types.Func)(0xc0003e18b0),(*types.Func)(0xc0003e19a0),(*types.Func)(0xc0003e1ae0),(*types.Func)(0xc0003e1bd0),(*types.Func)(0xc0003e1d10),(*types.Func)(0xc0003e1e00),(*types.Func)(0xc0003e1ef0),(*types.Func)(0xc0003e4050),(*types.Func)(0xc0003e4190),(*types.Func)(0xc0003e42d0),(*types.Func)(0xc0003e4410),(*types.Func)(0xc0003e4550),(*types.Func)(0xc0003e4690),(*types.Func)(0xc0003e47d0),(*types.Func)(0xc0003e4910),(*types.Func)(0xc0003e4a50),(*types.Func)(0xc0003e4b90)}}