Node


1   package polyglot.ast;
2   
3   import polyglot.util.Copy;
4   import polyglot.util.CodeWriter;
5   import polyglot.util.Position;
6   import polyglot.types.Type;
7   import polyglot.visit.*;
8   import java.util.List  ;
9   
10  /**
11   * A <code>Node</code> represents an AST node.  All AST nodes must implement
12   * this interface.  Nodes should be immutable: methods which set fields
13   * of the node should copy the node, set the field in the copy, and then
14   * return the copy.
15   */
16  public interface Node extends JL, Copy
17  {
18      /**
19       * Set the delegate of the node.
20       */
21      Node del(JL del);
22  
23      /**
24       * Get the node's delegate.
25       */
26      JL del();
27  
28      /**
29       * Set the extension of the node.
30       */
31      Node ext(Ext ext);
32  
33      /**
34       * Get the node's extension.
35       */
36      Ext ext();
37  
38      /**
39       * Set the node's nth extension, n &gt;= 1.
40       */
41      Node ext(int n, Ext ext);
42  
43      /**
44       * Get the node's nth extension, n &gt;= 1.
45       */
46      Ext ext(int n);
47  
48      /**
49       * Get the position of the node in the source file.  Returns null if
50       * the position is not set.
51       */
52      Position position();
53  
54      /** Create a copy of the node with a new position. */
55      Node position(Position position);
56  
57      /**
58       * Visit the node.  This method is equivalent to
59       * <code>visitEdge(null, v)</code>.
60       *
61       * @param v The visitor which will traverse/rewrite the AST.
62       * @return A new AST if a change was made, or <code>this</code>.
63       */
64      Node visit(NodeVisitor v);
65  
66      /**
67       * Visit the node, passing in the node's parent.  This method is called by
68       * a <code>NodeVisitor</code> to traverse the AST starting at this node.
69       * This method should call the <code>override</code>, <code>enter</code>,
70       * and <code>leave<code> methods of the visitor.  The method may return a
71       * new version of the node.
72       *
73       * @param parent The parent of <code>this</code> in the AST.
74       * @param v The visitor which will traverse/rewrite the AST.
75       * @return A new AST if a change was made, or <code>this</code>.
76       */
77      Node visitEdge(Node parent, NodeVisitor v);
78  
79      /**
80       * Visit a single child of the node.
81       *
82       * @param v The visitor which will traverse/rewrite the AST.
83       * @param child The child to visit.
84       * @return The result of <code>child.visit(v)</code>, or <code>null</code>
85       * if <code>child</code> was <code>null</code>.
86       */
87      Node visitChild(Node child, NodeVisitor v);
88  
89      /**
90       * Visit all the elements of a list.
91       * @param l The list to visit.
92       * @param v The visitor to use.
93       * @return A new list with each element from the old list
94       *         replaced by the result of visiting that element.
95       *         If <code>l</code> is a <code>TypedList</code>, the
96       *         new list will also be typed with the same type as 
97       *         <code>l</code>.  If <code>l</code> is <code>null</code>,
98       *         <code>null</code> is returned.
99       */
100     public List   visitList(List   l, NodeVisitor v);
101 
102     /**
103      * Get the expected type of a child expression of <code>this</code>.
104      * The expected type is determined by the context in that the child occurs
105      * (e.g., for <code>x = e</code>, the expected type of <code>e</code> is
106      * the declared type of <code>x</code>.
107      *
108      * The expected type should impose the least constraints on the child's
109      * type that are allowed by the parent node.
110      *
111      * @param child A child expression of this node.
112      * @param av An ascription visitor.
113      * @return The expected type of <code>child</code>.
114      */
115     Type childExpectedType(Expr child, AscriptionVisitor av);
116 
117     /**
118      * Dump the AST node for debugging purposes.
119      */
120     void dump(CodeWriter w);
121 }
122
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