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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ast
import "go/token"
type ObjKind int
// The list of possible Object kinds.
const (
Err ObjKind = iota // object kind unknown (forward reference or error)
Pkg // package
Con // constant
Typ // type
Var // variable
Fun // function or method
)
// An Object describes a language entity such as a package,
// constant, type, variable, or function (incl. methods).
//
type Object struct {
Kind ObjKind
Pos token.Position // declaration position
Name string // declared name
Scope *Scope // scope in which the Object is declared
}
func NewObj(kind ObjKind, pos token.Position, name string) *Object {
return &Object{kind, pos, name, nil}
}
// IsExported returns whether obj is exported.
func (obj *Object) IsExported() bool { return IsExported(obj.Name) }
// A Scope maintains the set of named language entities visible
// in the scope and a link to the immediately surrounding (outer)
// scope.
//
type Scope struct {
Outer *Scope
Objects map[string]*Object
}
// NewScope creates a new scope nested in the outer scope.
func NewScope(outer *Scope) *Scope { return &Scope{outer, make(map[string]*Object)} }
// Declare attempts to insert a named object into the scope s.
// If the scope does not contain an object with that name yet,
// Declare inserts the object, and the result is true. Otherwise,
// the scope remains unchanged and the result is false.
func (s *Scope) Declare(obj *Object) bool {
if obj.Name != "_" {
if _, found := s.Objects[obj.Name]; found {
return false
}
s.Objects[obj.Name] = obj
}
return true
}
// Lookup looks up an object in the current scope chain.
// The result is nil if the object is not found.
//
func (s *Scope) Lookup(name string) *Object {
for ; s != nil; s = s.Outer {
if obj, found := s.Objects[name]; found {
return obj
}
}
return nil
}
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