Goのスコープについて考えてみよう #golang ref: http://qiita.com/tenntenn/items/ac5940dfbca703183fdf

file0.go

package main

import "fmt"

func main() {
    const message = "hello, world"
    fmt.Println(message)
}

file1.go

package main

import (
    myfmt "fmt"
)

func main() {
    var string string = "HELLO"
    myfmt.Println(string)
}

file2.go

fset := token.NewFileSet()
f, err := parser.ParseFile(fset, "sample.go", src, 0)
if err != nil {
    log.Fatalln("Error:", err)
}

file3.go

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

file4.go

ast.Inspect(f, func(n ast.Node) bool {
    if ident, ok := n.(*ast.Ident); ok {
        // TODO: 識別子のスコープを取得する
    }
    return true
})

file5.go

innerMost := pkg.Scope().Innermost(ident.Pos())
s, _ := innerMost.LookupParent(ident.Name, ident.Pos())

file6.go

package main

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

// sample.go
const src = `package main

import "fmt"

func main() {
    const message = "hello, world"
    fmt.Println(message)
}`

func main() {
    fset := token.NewFileSet()
    f, err := parser.ParseFile(fset, "sample.go", src, 0)
    if err != nil {
        log.Fatalln("Error:", err)
    }

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

    scopes := map[*types.Scope]struct{}{}
    ast.Inspect(f, func(n ast.Node) bool {
        if ident, ok := n.(*ast.Ident); ok {
            innerMost := pkg.Scope().Innermost(ident.Pos())
            s, _ := innerMost.LookupParent(ident.Name, ident.Pos())
            if s != nil {
                scopes[s] = struct{}{}
            }
        }
        return true
    })

    fmt.Println("====", len(scopes), "scopes ====")
    for s := range scopes {
        fmt.Println(s)
    }
}

file7.txt

==== 3 scopes ====
package "main" scope 0x4203ff6d0 {
.  func main.main()
}
sample.go scope 0x4203ff7c0 {
.  package fmt
}
function scope 0x42053d630 {
.  const message untyped string
}

file8.go

package main

import (
    myfmt "fmt"
)

func main() {
    var string string = "HELLO"
    myfmt.Println(string)
}

file9.txt

==== 4 scopes ====
package "main" scope 0x4203ff6d0 {
.  func main.main()
}
sample.go scope 0x4203ff7c0 {
.  package myfmt ("fmt")
}
universe scope 0x4203fe1e0 {
.  builtin append
.  type bool bool
.  type byte byte
.  builtin cap
.  builtin close
.  builtin complex
.  type complex128 complex128
.  type complex64 complex64
.  builtin copy
.  builtin delete
.  type error interface{Error() string}
.  const false untyped bool
.  type float32 float32
.  type float64 float64
.  builtin imag
.  type int int
.  type int16 int16
.  type int32 int32
.  type int64 int64
.  type int8 int8
.  const iota untyped int
.  builtin len
.  builtin make
.  builtin new
.  nil
.  builtin panic
.  builtin print
.  builtin println
.  builtin real
.  builtin recover
.  type rune rune
.  type string string
.  const true untyped bool
.  type uint uint
.  type uint16 uint16
.  type uint32 uint32
.  type uint64 uint64
.  type uint8 uint8
.  type uintptr uintptr
}
function scope 0x42053d630 {
.  var string string
}