libgo/go/go/types/objset.go

   1 // Copyright 2013 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // This file implements objsets.
   6 //
   7 // An objset is similar to a Scope but objset elements
   8 // are identified by their unique id, instead of their
   9 // object name.
  10
  11 package types
  12
  13 // An objset is a set of objects identified by their unique id.
  14 // The zero value for objset is a ready-to-use empty objset.
  15 type objset map[string]Object // initialized lazily
  16
  17 // insert attempts to insert an object obj into objset s.
  18 // If s already contains an alternative object alt with
  19 // the same name, insert leaves s unchanged and returns alt.
  20 // Otherwise it inserts obj and returns nil.
  21 func (s *objset) insert(obj Object) Object {
  22         id := obj.Id()
  23         if alt := (*s)[id]; alt != nil {
  24                 return alt
  25         }
  26         if *s == nil {
  27                 *s = make(map[string]Object)
  28         }
  29         (*s)[id] = obj
  30         return nil
  31 }