cpp/third_party/antlr4-cpp-runtime-4/runtime/src/RuleContext.h

/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

#pragma once

#include "tree/ParseTree.h"

namespace antlr4 {

  /** A rule context is a record of a single rule invocation.
   *
   *  We form a stack of these context objects using the parent
   *  pointer. A parent pointer of null indicates that the current
   *  context is the bottom of the stack. The ParserRuleContext subclass
   *  as a children list so that we can turn this data structure into a
   *  tree.
   *
   *  The root node always has a null pointer and invokingState of -1.
   *
   *  Upon entry to parsing, the first invoked rule function creates a
   *  context object (asubclass specialized for that rule such as
   *  SContext) and makes it the root of a parse tree, recorded by field
   *  Parser._ctx.
   *
   *  public final SContext s() throws RecognitionException {
   *      SContext _localctx = new SContext(_ctx, getState()); <-- create new node
   *      enterRule(_localctx, 0, RULE_s);                     <-- push it
   *      ...
   *      exitRule();                                          <-- pop back to _localctx
   *      return _localctx;
   *  }
   *
   *  A subsequent rule invocation of r from the start rule s pushes a
   *  new context object for r whose parent points at s and use invoking
   *  state is the state with r emanating as edge label.
   *
   *  The invokingState fields from a context object to the root
   *  together form a stack of rule indication states where the root
   *  (bottom of the stack) has a -1 sentinel value. If we invoke start
   *  symbol s then call r1, which calls r2, the  would look like
   *  this:
   *
   *     SContext[-1]   <- root node (bottom of the stack)
   *     R1Context[p]   <- p in rule s called r1
   *     R2Context[q]   <- q in rule r1 called r2
   *
   *  So the top of the stack, _ctx, represents a call to the current
   *  rule and it holds the return address from another rule that invoke
   *  to this rule. To invoke a rule, we must always have a current context.
   *
   *  The parent contexts are useful for computing lookahead sets and
   *  getting error information.
   *
   *  These objects are used during parsing and prediction.
   *  For the special case of parsers, we use the subclass
   *  ParserRuleContext.
   *
   *  @see ParserRuleContext
   */
  class ANTLR4CPP_PUBLIC RuleContext : public tree::ParseTree {
  public:
    /// What state invoked the rule associated with this context?
    /// The "return address" is the followState of invokingState
    /// If parent is null, this should be -1 and this context object represents the start rule.
    size_t invokingState;

    RuleContext();
    RuleContext(RuleContext *parent, size_t invokingState);

    virtual int depth();

    /// A context is empty if there is no invoking state; meaning nobody called current context.
    virtual bool isEmpty();

    // satisfy the ParseTree / SyntaxTree interface

    virtual misc::Interval getSourceInterval() override;

    virtual std::string getText() override;

    virtual size_t getRuleIndex() const;

    /** For rule associated with this parse tree internal node, return
     *  the outer alternative number used to match the input. Default
     *  implementation does not compute nor store this alt num. Create
     *  a subclass of ParserRuleContext with backing field and set
     *  option contextSuperClass.
     *  to set it.
     *
     *  @since 4.5.3
     */
    virtual size_t getAltNumber() const;

    /** Set the outer alternative number for this context node. Default
     *  implementation does nothing to avoid backing field overhead for
     *  trees that don't need it.  Create
     *  a subclass of ParserRuleContext with backing field and set
     *  option contextSuperClass.
     *
     *  @since 4.5.3
     */
    virtual void setAltNumber(size_t altNumber);

    virtual antlrcpp::Any accept(tree::ParseTreeVisitor *visitor) override;

    /// <summary>
    /// Print out a whole tree, not just a node, in LISP format
    ///  (root child1 .. childN). Print just a node if this is a leaf.
    ///  We have to know the recognizer so we can get rule names.
    /// </summary>
    virtual std::string toStringTree(Parser *recog, bool pretty = false) override;

    /// <summary>
    /// Print out a whole tree, not just a node, in LISP format
    ///  (root child1 .. childN). Print just a node if this is a leaf.
    /// </summary>
    virtual std::string toStringTree(std::vector<std::string> &ruleNames, bool pretty = false);

    virtual std::string toStringTree(bool pretty = false) override;
    virtual std::string toString() override;
    std::string toString(Recognizer *recog);
    std::string toString(const std::vector<std::string> &ruleNames);

    // recog null unless ParserRuleContext, in which case we use subclass toString(...)
    std::string toString(Recognizer *recog, RuleContext *stop);

    virtual std::string toString(const std::vector<std::string> &ruleNames, RuleContext *stop);

    bool equal(const RuleContext &other) { return this == &other; } // Simple address comparison.

  private:
    void InitializeInstanceFields();
  };

} // namespace antlr4