org.antlr.tool

Class GrammarSanity

java.lang.Object

org.antlr.tool.GrammarSanity

public class GrammarSanity
extends Object

Factor out routines that check sanity of rules, alts, grammars, etc..

Field Summary

Fields

Modifier and Type	Field and Description
protected Grammar	grammar
protected Set<Rule>	visitedDuringRecursionCheck The checkForLeftRecursion method needs to track what rules it has visited to track infinite recursion.

Constructor Summary

Constructors

Constructor and Description
GrammarSanity(Grammar grammar)

Method Summary

Methods

Modifier and Type	Method and Description
protected void	addRulesToCycle(Rule targetRule, Rule enclosingRule, List<Set<Rule>> listOfRecursiveCycles) enclosingRuleName calls targetRuleName, find the cycle containing the target and add the caller.
List<Set<Rule>>	checkAllRulesForLeftRecursion() Check all rules for infinite left recursion before analysis.
void	checkRuleReference(GrammarAST scopeAST, GrammarAST refAST, GrammarAST argsAST, String currentRuleName)
void	ensureAltIsSimpleNodeOrTree(GrammarAST altAST, GrammarAST elementAST, int outerAltNum) Rules in tree grammar that use -> rewrites and are spitting out templates via output=template and then use rewrite=true must only use -> on alts that are simple nodes or trees or single rule refs that match either nodes or trees.
protected boolean	isNextNonActionElementEOA(GrammarAST t)
protected boolean	isValidSimpleElementNode(GrammarAST t)
protected boolean	traceStatesLookingForLeftRecursion(NFAState s, Set visitedStates, List<Set<Rule>> listOfRecursiveCycles) From state s, look for any transition to a rule that is currently being traced.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

visitedDuringRecursionCheck

protected Set<Rule> visitedDuringRecursionCheck

The checkForLeftRecursion method needs to track what rules it has visited to track infinite recursion.

grammar

protected Grammar grammar

Constructor Detail

GrammarSanity

public GrammarSanity(Grammar grammar)

Method Detail

checkAllRulesForLeftRecursion

public List<Set<Rule>> checkAllRulesForLeftRecursion()

Check all rules for infinite left recursion before analysis. Return list of troublesome rule cycles. This method has two side-effects: it notifies the error manager that we have problems and it sets the list of recursive rules that we should ignore during analysis.

traceStatesLookingForLeftRecursion

protected boolean traceStatesLookingForLeftRecursion(NFAState s,
                                         Set visitedStates,
                                         List<Set<Rule>> listOfRecursiveCycles)

From state s, look for any transition to a rule that is currently being traced. When tracing r, visitedDuringRecursionCheck has r initially. If you reach an accept state, return but notify the invoking rule that it is nullable, which implies that invoking rule must look at follow transition for that invoking state. The visitedStates tracks visited states within a single rule so we can avoid epsilon-loop-induced infinite recursion here. Keep filling the cycles in listOfRecursiveCycles and also, as a side-effect, set leftRecursiveRules.

addRulesToCycle

protected void addRulesToCycle(Rule targetRule,
                   Rule enclosingRule,
                   List<Set<Rule>> listOfRecursiveCycles)

enclosingRuleName calls targetRuleName, find the cycle containing the target and add the caller. Find the cycle containing the caller and add the target. If no cycles contain either, then create a new cycle. listOfRecursiveCycles is List> that holds a list of cycles (sets of rule names).

checkRuleReference

public void checkRuleReference(GrammarAST scopeAST,
                      GrammarAST refAST,
                      GrammarAST argsAST,
                      String currentRuleName)

ensureAltIsSimpleNodeOrTree

public void ensureAltIsSimpleNodeOrTree(GrammarAST altAST,
                               GrammarAST elementAST,
                               int outerAltNum)

Rules in tree grammar that use -> rewrites and are spitting out templates via output=template and then use rewrite=true must only use -> on alts that are simple nodes or trees or single rule refs that match either nodes or trees. The altAST is the ALT node for an ALT. Verify that its first child is simple. Must be either ( ALT ^( A B ) ) or ( ALT A ) or other element. Ignore predicates in front and labels.

isValidSimpleElementNode

protected boolean isValidSimpleElementNode(GrammarAST t)

isNextNonActionElementEOA

protected boolean isNextNonActionElementEOA(GrammarAST t)