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package edu.rice.cs.drjava.model.repl.types;
/** <p>A lightweight visitor for traversing (in depth-first order) arbitrary ASTGen-produced
* trees. Unlike the Visitor classes generated for a specific AST, implementations of
* TreeWalker are defined for all ASTs. They are more limited, having far fewer hooks
* available for manipulating the traversal process and handling different types of nodes.
* This minimal interface is enough, however, for simple visitors which aren't concerned
* with the semantic content of a tree and simply need to traverse its structure.</p>
*
* <p>When passed to a node's {@code walk()} method, a TreeWalker can expect to receive
* a specific sequence of method calls: {@link #visitNode}, then {@link #visitField}
* and a recursive invocation for each of the node's fields. "Recursive invocations"
* include additional {@code visitNode()} calls and invocations of the the other "visit"
* methods for handling Strings, lists, primitives, and objects of unrecognized type.
* (Note that the method to call is determined statically based on the field's declared
* type, not at runtime.) Clients can prevent recursion into a non-atomic element's
* children by returning {@code false} in the appropriate visit method.</p>
*/
public abstract class TreeWalker {
/** Visit an AST node. Return {@code true} to recur on each of the node's fields. */
public boolean visitNode(java.lang.Object node, java.lang.String type, int fields) { return true; }
/** Visit an AST node's field. Return {@code true} to recur on the field's value. */
public boolean visitNodeField(java.lang.String name, java.lang.Object value) { return true; }
/** Signal the end of recursion on an AST node's field. */
public void endNodeField(java.lang.String name, java.lang.Object value) {}
/** Signal the end of a sequence of node fields. */
public void endNode(java.lang.Object node, java.lang.String type, int fields) {}
/** Visit an Iterable or array. Return {@code true} to recur on each element. */
public boolean visitIterated(java.lang.Object iterable) { return true; }
/** Visit an iterated element. Return {@code true} to recur on the element value. */
public boolean visitIteratedElement(int index, java.lang.Object element) { return true; }
/** Signal the end of recursion on an iterated element. */
public void endIteratedElement(int index, java.lang.Object element) {}
/** Signal the end of a sequence of iterated elements. */
public void endIterated(java.lang.Object iterable, int size) {}
/** Visit a non-empty option-typed value. Return {@code true} to recur on the nested value. */
public boolean visitNonEmptyOption(java.lang.Object option) { return true; }
/** Signal the end of recursion on a non-empty option. */
public void endNonEmptyOption(java.lang.Object option) {}
/** Visit an empty option-typed value. */
public void visitEmptyOption(java.lang.Object option) {}
/** Visit a tuple-typed value. Return {@code true} to recur on the nested elements. */
public boolean visitTuple(java.lang.Object tuple, int arity) { return true; }
/** Visit a tuple element. Return {@code true} to recur on the element value. */
public boolean visitTupleElement(int index, java.lang.Object element) { return true; }
/** Signal the end of a tuple element. */
public void endTupleElement(int index, java.lang.Object element) {}
/** Signal the end of a sequence of tuple elements. */
public void endTuple(java.lang.Object tuple, int arity) {}
/** Visit a string value. */
public void visitString(java.lang.String s) {}
/**
* Visit an object that is not known statically to have an AST Node or
* other supported type.
*/
public void visitUnknownObject(java.lang.Object o) {}
/**
* Visit a null reference. This is called rather than {@code visitNode}, {@code visitList},
* {@code visitUnknownObject}, etc., where a field or element's value is {@code null}.
*/
public void visitNull() {}
/** Visit a boolean primitive. */
public void visitBoolean(boolean b) {}
/** Visit a char primitive. */
public void visitChar(char c) {}
/** Visit a byte primitive. */
public void visitByte(byte b) {}
/** Visit a short primitive. */
public void visitShort(short s) {}
/** Visit a int primitive. */
public void visitInt(int i) {}
/** Visit a long primitive. */
public void visitLong(long l) {}
/** Visit a float primitive. */
public void visitFloat(float f) {}
/** Visit a double primitive. */
public void visitDouble(double d) {}
}