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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.
// This file implements scopes and the objects they contain.
package ast
import (
"bytes"
"fmt"
"go/token"
)
// A Scope maintains the set of named language entities declared
// 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 {
const n = 4 // initial scope capacity
return &Scope{outer, make(map[string]*Object, n)}
}
// Lookup returns the object with the given name if it is
// found in scope s, otherwise it returns nil. Outer scopes
// are ignored.
//
func (s *Scope) Lookup(name string) *Object {
return s.Objects[name]
}
// Insert attempts to insert a named object obj into the scope s.
// If the scope already contains an object alt with the same name,
// Insert leaves the scope unchanged and returns alt. Otherwise
// it inserts obj and returns nil.
//
func (s *Scope) Insert(obj *Object) (alt *Object) {
if alt = s.Objects[obj.Name]; alt == nil {
s.Objects[obj.Name] = obj
}
return
}
// Debugging support
func (s *Scope) String() string {
var buf bytes.Buffer
fmt.Fprintf(&buf, "scope %p {", s)
if s != nil && len(s.Objects) > 0 {
fmt.Fprintln(&buf)
for _, obj := range s.Objects {
fmt.Fprintf(&buf, "\t%s %s\n", obj.Kind, obj.Name)
}
}
fmt.Fprintf(&buf, "}\n")
return buf.String()
}
// ----------------------------------------------------------------------------
// Objects
// An Object describes a named language entity such as a package,
// constant, type, variable, function (incl. methods), or label.
//
// The Data fields contains object-specific data:
//
// Kind Data type Data value
// Pkg *Scope package scope
// Con int iota for the respective declaration
//
type Object struct {
Kind ObjKind
Name string // declared name
Decl interface{} // corresponding Field, XxxSpec, FuncDecl, LabeledStmt, AssignStmt, Scope; or nil
Data interface{} // object-specific data; or nil
Type interface{} // placeholder for type information; may be nil
}
// NewObj creates a new object of a given kind and name.
func NewObj(kind ObjKind, name string) *Object {
return &Object{Kind: kind, Name: name}
}
// Pos computes the source position of the declaration of an object name.
// The result may be an invalid position if it cannot be computed
// (obj.Decl may be nil or not correct).
func (obj *Object) Pos() token.Pos {
name := obj.Name
switch d := obj.Decl.(type) {
case *Field:
for _, n := range d.Names {
if n.Name == name {
return n.Pos()
}
}
case *ImportSpec:
if d.Name != nil && d.Name.Name == name {
return d.Name.Pos()
}
return d.Path.Pos()
case *ValueSpec:
for _, n := range d.Names {
if n.Name == name {
return n.Pos()
}
}
case *TypeSpec:
if d.Name.Name == name {
return d.Name.Pos()
}
case *FuncDecl:
if d.Name.Name == name {
return d.Name.Pos()
}
case *LabeledStmt:
if d.Label.Name == name {
return d.Label.Pos()
}
case *AssignStmt:
for _, x := range d.Lhs {
if ident, isIdent := x.(*Ident); isIdent && ident.Name == name {
return ident.Pos()
}
}
case *Scope:
// predeclared object - nothing to do for now
}
return token.NoPos
}
// ObjKind describes what an object represents.
type ObjKind int
// The list of possible Object kinds.
const (
Bad ObjKind = iota // for error handling
Pkg // package
Con // constant
Typ // type
Var // variable
Fun // function or method
Lbl // label
)
var objKindStrings = [...]string{
Bad: "bad",
Pkg: "package",
Con: "const",
Typ: "type",
Var: "var",
Fun: "func",
Lbl: "label",
}
func (kind ObjKind) String() string { return objKindStrings[kind] }
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