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With inspiration from other libraries
/*
* 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.
*/
package org.antlr.v4.analysis;
import org.antlr.runtime.ANTLRStringStream;
import org.antlr.runtime.CommonTokenStream;
import org.antlr.runtime.ParserRuleReturnScope;
import org.antlr.runtime.RecognitionException;
import org.antlr.runtime.Token;
import org.antlr.v4.Tool;
import org.antlr.v4.misc.OrderedHashMap;
import org.antlr.v4.parse.ANTLRLexer;
import org.antlr.v4.parse.ANTLRParser;
import org.antlr.v4.parse.GrammarASTAdaptor;
import org.antlr.v4.parse.ScopeParser;
import org.antlr.v4.parse.ToolANTLRParser;
import org.antlr.v4.runtime.misc.Pair;
import org.antlr.v4.semantics.BasicSemanticChecks;
import org.antlr.v4.semantics.RuleCollector;
import org.antlr.v4.tool.AttributeDict;
import org.antlr.v4.tool.ErrorType;
import org.antlr.v4.tool.Grammar;
import org.antlr.v4.tool.GrammarTransformPipeline;
import org.antlr.v4.tool.LabelElementPair;
import org.antlr.v4.tool.LeftRecursiveRule;
import org.antlr.v4.tool.Rule;
import org.antlr.v4.tool.ast.ActionAST;
import org.antlr.v4.tool.ast.AltAST;
import org.antlr.v4.tool.ast.BlockAST;
import org.antlr.v4.tool.ast.GrammarAST;
import org.antlr.v4.tool.ast.GrammarASTWithOptions;
import org.antlr.v4.tool.ast.GrammarRootAST;
import org.antlr.v4.tool.ast.RuleAST;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
/** Remove left-recursive rule refs, add precedence args to recursive rule refs.
* Rewrite rule so we can create ATN.
*
* MODIFIES grammar AST in place.
*/
public class LeftRecursiveRuleTransformer {
public static final String PRECEDENCE_OPTION_NAME = "p";
public static final String TOKENINDEX_OPTION_NAME = "tokenIndex";
public GrammarRootAST ast;
public Collection rules;
public Grammar g;
public Tool tool;
public LeftRecursiveRuleTransformer(GrammarRootAST ast, Collection rules, Grammar g) {
this.ast = ast;
this.rules = rules;
this.g = g;
this.tool = g.tool;
}
public void translateLeftRecursiveRules() {
String language = g.getOptionString("language");
// translate all recursive rules
List leftRecursiveRuleNames = new ArrayList();
for (Rule r : rules) {
if ( !Grammar.isTokenName(r.name) ) {
if ( LeftRecursiveRuleAnalyzer.hasImmediateRecursiveRuleRefs(r.ast, r.name) ) {
boolean fitsPattern = translateLeftRecursiveRule(ast, (LeftRecursiveRule)r, language);
if ( fitsPattern ) {
leftRecursiveRuleNames.add(r.name);
}
else { // better given an error that non-conforming left-recursion exists
tool.errMgr.grammarError(ErrorType.NONCONFORMING_LR_RULE, g.fileName, ((GrammarAST)r.ast.getChild(0)).token, r.name);
}
}
}
}
// update all refs to recursive rules to have [0] argument
for (GrammarAST r : ast.getNodesWithType(ANTLRParser.RULE_REF)) {
if ( r.getParent().getType()==ANTLRParser.RULE ) continue; // must be rule def
if ( ((GrammarASTWithOptions)r).getOptionString(PRECEDENCE_OPTION_NAME) != null ) continue; // already has arg; must be in rewritten rule
if ( leftRecursiveRuleNames.contains(r.getText()) ) {
// found ref to recursive rule not already rewritten with arg
((GrammarASTWithOptions)r).setOption(PRECEDENCE_OPTION_NAME, (GrammarAST)new GrammarASTAdaptor().create(ANTLRParser.INT, "0"));
}
}
}
/** Return true if successful */
public boolean translateLeftRecursiveRule(GrammarRootAST ast,
LeftRecursiveRule r,
String language)
{
//tool.log("grammar", ruleAST.toStringTree());
GrammarAST prevRuleAST = r.ast;
String ruleName = prevRuleAST.getChild(0).getText();
LeftRecursiveRuleAnalyzer leftRecursiveRuleWalker =
new LeftRecursiveRuleAnalyzer(prevRuleAST, tool, ruleName, language);
boolean isLeftRec;
try {
// System.out.println("TESTING ---------------\n"+
// leftRecursiveRuleWalker.text(ruleAST));
isLeftRec = leftRecursiveRuleWalker.rec_rule();
}
catch (RecognitionException re) {
isLeftRec = false; // didn't match; oh well
}
if ( !isLeftRec ) return false;
// replace old rule's AST; first create text of altered rule
GrammarAST RULES = (GrammarAST)ast.getFirstChildWithType(ANTLRParser.RULES);
String newRuleText = leftRecursiveRuleWalker.getArtificialOpPrecRule();
// System.out.println("created: "+newRuleText);
// now parse within the context of the grammar that originally created
// the AST we are transforming. This could be an imported grammar so
// we cannot just reference this.g because the role might come from
// the imported grammar and not the root grammar (this.g)
RuleAST t = parseArtificialRule(prevRuleAST.g, newRuleText);
// reuse the name token from the original AST since it refers to the proper source location in the original grammar
((GrammarAST)t.getChild(0)).token = ((GrammarAST)prevRuleAST.getChild(0)).getToken();
// update grammar AST and set rule's AST.
RULES.setChild(prevRuleAST.getChildIndex(), t);
r.ast = t;
// Reduce sets in newly created rule tree
GrammarTransformPipeline transform = new GrammarTransformPipeline(g, g.tool);
transform.reduceBlocksToSets(r.ast);
transform.expandParameterizedLoops(r.ast);
// Rerun semantic checks on the new rule
RuleCollector ruleCollector = new RuleCollector(g);
ruleCollector.visit(t, "rule");
BasicSemanticChecks basics = new BasicSemanticChecks(g, ruleCollector);
// disable the assoc element option checks because they are already
// handled for the pre-transformed rule.
basics.checkAssocElementOption = false;
basics.visit(t, "rule");
// track recursive alt info for codegen
r.recPrimaryAlts = new ArrayList();
r.recPrimaryAlts.addAll(leftRecursiveRuleWalker.prefixAndOtherAlts);
if (r.recPrimaryAlts.isEmpty()) {
tool.errMgr.grammarError(ErrorType.NO_NON_LR_ALTS, g.fileName, ((GrammarAST)r.ast.getChild(0)).getToken(), r.name);
}
r.recOpAlts = new OrderedHashMap();
r.recOpAlts.putAll(leftRecursiveRuleWalker.binaryAlts);
r.recOpAlts.putAll(leftRecursiveRuleWalker.ternaryAlts);
r.recOpAlts.putAll(leftRecursiveRuleWalker.suffixAlts);
// walk alt info records and set their altAST to point to appropriate ALT subtree
// from freshly created AST
setAltASTPointers(r, t);
// update Rule to just one alt and add prec alt
ActionAST arg = (ActionAST)r.ast.getFirstChildWithType(ANTLRParser.ARG_ACTION);
if ( arg!=null ) {
r.args = ScopeParser.parseTypedArgList(arg, arg.getText(), g);
r.args.type = AttributeDict.DictType.ARG;
r.args.ast = arg;
arg.resolver = r.alt[1]; // todo: isn't this Rule or something?
}
// define labels on recursive rule refs we delete; they don't point to nodes of course
// these are so $label in action translation works
for (Pair pair : leftRecursiveRuleWalker.leftRecursiveRuleRefLabels) {
GrammarAST labelNode = pair.a;
GrammarAST labelOpNode = (GrammarAST)labelNode.getParent();
GrammarAST elementNode = (GrammarAST)labelOpNode.getChild(1);
LabelElementPair lp = new LabelElementPair(g, labelNode, elementNode, labelOpNode.getType());
r.alt[1].labelDefs.map(labelNode.getText(), lp);
}
// copy to rule from walker
r.leftRecursiveRuleRefLabels = leftRecursiveRuleWalker.leftRecursiveRuleRefLabels;
tool.log("grammar", "added: "+t.toStringTree());
return true;
}
public RuleAST parseArtificialRule(final Grammar g, String ruleText) {
ANTLRLexer lexer = new ANTLRLexer(new ANTLRStringStream(ruleText));
GrammarASTAdaptor adaptor = new GrammarASTAdaptor(lexer.getCharStream());
CommonTokenStream tokens = new CommonTokenStream(lexer);
lexer.tokens = tokens;
ToolANTLRParser p = new ToolANTLRParser(tokens, tool);
p.setTreeAdaptor(adaptor);
Token ruleStart = null;
try {
ParserRuleReturnScope r = p.rule();
RuleAST tree = (RuleAST)r.getTree();
ruleStart = (Token)r.getStart();
GrammarTransformPipeline.setGrammarPtr(g, tree);
GrammarTransformPipeline.augmentTokensWithOriginalPosition(g, tree);
return tree;
}
catch (Exception e) {
tool.errMgr.toolError(ErrorType.INTERNAL_ERROR,
e,
ruleStart,
"error parsing rule created during left-recursion detection: "+ruleText);
}
return null;
}
/**
*
* (RULE e int _p (returns int v)
* (BLOCK
* (ALT
* (BLOCK
* (ALT INT {$v = $INT.int;})
* (ALT '(' (= x e) ')' {$v = $x.v;})
* (ALT ID))
* (* (BLOCK
* (OPTIONS ...)
* (ALT {7 >= $_p}? '*' (= b e) {$v = $a.v * $b.v;})
* (ALT {6 >= $_p}? '+' (= b e) {$v = $a.v + $b.v;})
* (ALT {3 >= $_p}? '++') (ALT {2 >= $_p}? '--'))))))
*
*/
public void setAltASTPointers(LeftRecursiveRule r, RuleAST t) {
// System.out.println("RULE: "+t.toStringTree());
BlockAST ruleBlk = (BlockAST)t.getFirstChildWithType(ANTLRParser.BLOCK);
AltAST mainAlt = (AltAST)ruleBlk.getChild(0);
BlockAST primaryBlk = (BlockAST)mainAlt.getChild(0);
BlockAST opsBlk = (BlockAST)mainAlt.getChild(1).getChild(0); // (* BLOCK ...)
for (int i = 0; i < r.recPrimaryAlts.size(); i++) {
LeftRecursiveRuleAltInfo altInfo = r.recPrimaryAlts.get(i);
altInfo.altAST = (AltAST)primaryBlk.getChild(i);
altInfo.altAST.leftRecursiveAltInfo = altInfo;
altInfo.originalAltAST.leftRecursiveAltInfo = altInfo;
// altInfo.originalAltAST.parent = altInfo.altAST.parent;
// System.out.println(altInfo.altAST.toStringTree());
}
for (int i = 0; i < r.recOpAlts.size(); i++) {
LeftRecursiveRuleAltInfo altInfo = r.recOpAlts.getElement(i);
altInfo.altAST = (AltAST)opsBlk.getChild(i);
altInfo.altAST.leftRecursiveAltInfo = altInfo;
altInfo.originalAltAST.leftRecursiveAltInfo = altInfo;
// altInfo.originalAltAST.parent = altInfo.altAST.parent;
// System.out.println(altInfo.altAST.toStringTree());
}
}
}