Package org.antlr.v4.runtime

Class ParserRuleContext

  • All Implemented Interfaces:
    ParseTree, RuleNode, SyntaxTree, Tree
    Direct Known Subclasses:
    InterpreterRuleContext, RuleContextWithAltNum
    public class ParserRuleContext
extends RuleContext
    A rule invocation record for parsing. Contains all of the information about the current rule not stored in the RuleContext. It handles parse tree children list, Any ATN state tracing, and the default values available for rule invocations: start, stop, rule index, current alt number. Subclasses made for each rule and grammar track the parameters, return values, locals, and labels specific to that rule. These are the objects that are returned from rules. Note text is not an actual field of a rule return value; it is computed from start and stop using the input stream's toString() method. I could add a ctor to this so that we can pass in and store the input stream, but I'm not sure we want to do that. It would seem to be undefined to get the .text property anyway if the rule matches tokens from multiple input streams. I do not use getters for fields of objects that are used simply to group values such as this aggregate. The getters/setters are there to satisfy the superclass interface.

    • Field Detail

      • children

        public List<ParseTree> children
        If we are debugging or building a parse tree for a visitor, we need to track all of the tokens and rule invocations associated with this rule's context. This is empty for parsing w/o tree constr. operation because we don't the need to track the details about how we parse this rule.

      • start

        public Token start
        For debugging/tracing purposes, we want to track all of the nodes in the ATN traversed by the parser for a particular rule. This list indicates the sequence of ATN nodes used to match the elements of the children list. This list does not include ATN nodes and other rules used to match rule invocations. It traces the rule invocation node itself but nothing inside that other rule's ATN submachine. There is NOT a one-to-one correspondence between the children and states list. There are typically many nodes in the ATN traversed for each element in the children list. For example, for a rule invocation there is the invoking state and the following state. The parser setState() method updates field s and adds it to this list if we are debugging/tracing. This does not trace states visited during prediction.

      • stop

        public Token stop
        For debugging/tracing purposes, we want to track all of the nodes in the ATN traversed by the parser for a particular rule. This list indicates the sequence of ATN nodes used to match the elements of the children list. This list does not include ATN nodes and other rules used to match rule invocations. It traces the rule invocation node itself but nothing inside that other rule's ATN submachine. There is NOT a one-to-one correspondence between the children and states list. There are typically many nodes in the ATN traversed for each element in the children list. For example, for a rule invocation there is the invoking state and the following state. The parser setState() method updates field s and adds it to this list if we are debugging/tracing. This does not trace states visited during prediction.

      • exception

        public RecognitionException exception
        The exception that forced this rule to return. If the rule successfully completed, this is null.

    • Constructor Detail

      • ParserRuleContext

        public ParserRuleContext()

      • ParserRuleContext

        public ParserRuleContext​(ParserRuleContext parent,
                         int invokingStateNumber)

    • Method Detail

      • copyFrom

        public void copyFrom​(ParserRuleContext ctx)
        COPY a ctx (I'm deliberately not using copy constructor) to avoid confusion with creating node with parent. Does not copy children (except error leaves). This is used in the generated parser code to flip a generic XContext node for rule X to a YContext for alt label Y. In that sense, it is not really a generic copy function. If we do an error sync() at start of a rule, we might add error nodes to the generic XContext so this function must copy those nodes to the YContext as well else they are lost!

      • addAnyChild

        public <T extends ParseTree> T addAnyChild​(T t)
        Add a parse tree node to this as a child. Works for internal and leaf nodes. Does not set parent link; other add methods must do that. Other addChild methods call this. We cannot set the parent pointer of the incoming node because the existing interfaces do not have a setParent() method and I don't want to break backward compatibility for this.
        Since:
        4.7

      • addChild

        public TerminalNode addChild​(TerminalNode t)
        Add a token leaf node child and force its parent to be this node.

      • addErrorNode

        public ErrorNode addErrorNode​(ErrorNode errorNode)
        Add an error node child and force its parent to be this node.
        Since:
        4.7

      • removeLastChild

        public void removeLastChild()
        Used by enterOuterAlt to toss out a RuleContext previously added as we entered a rule. If we have # label, we will need to remove generic ruleContext object.

      • getChild

        public <T extends ParseTree> T getChild​(Class<? extends T> ctxType,
                                        int i)

      • getToken

        public TerminalNode getToken​(int ttype,
                             int i)

      • getRuleContext

        public <T extends ParserRuleContext> T getRuleContext​(Class<? extends T> ctxType,
                                                      int i)

      • getChildCount

        public int getChildCount()
        Description copied from interface: Tree
        How many children are there? If there is none, then this node represents a leaf node.
        Specified by:
        getChildCount in interface Tree
        Overrides:
        getChildCount in class RuleContext

      • getSourceInterval

        public Interval getSourceInterval()
        Description copied from interface: SyntaxTree
        Return an Interval indicating the index in the TokenStream of the first and last token associated with this subtree. If this node is a leaf, then the interval represents a single token and has interval i..i for token index i.

        An interval of i..i-1 indicates an empty interval at position i in the input stream, where 0 <= i <= the size of the input token stream. Currently, the code base can only have i=0..n-1 but in concept one could have an empty interval after EOF.

        If source interval is unknown, this returns Interval.INVALID.

        As a weird special case, the source interval for rules matched after EOF is unspecified.

        Specified by:
        getSourceInterval in interface SyntaxTree
        Overrides:
        getSourceInterval in class RuleContext

      • getStart

        public Token getStart()
        Get the initial token in this context. Note that the range from start to stop is inclusive, so for rules that do not consume anything (for example, zero length or error productions) this token may exceed stop.

      • getStop

        public Token getStop()
        Get the final token in this context. Note that the range from start to stop is inclusive, so for rules that do not consume anything (for example, zero length or error productions) this token may precede start.

      • toInfoString

        public String toInfoString​(Parser recognizer)
        Used for rule context info debugging during parse-time, not so much for ATN debugging