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The ANTLR 4 grammar compiler.
/*
* [The "BSD license"]
* Copyright (c) 2012 Terence Parr
* Copyright (c) 2012 Sam Harwell
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.antlr.v4.analysis;
import org.antlr.runtime.CommonToken;
import org.antlr.runtime.Token;
import org.antlr.runtime.TokenStream;
import org.antlr.runtime.tree.CommonTreeNodeStream;
import org.antlr.runtime.tree.Tree;
import org.antlr.v4.Tool;
import org.antlr.v4.codegen.CodeGenerator;
import org.antlr.v4.parse.ANTLRParser;
import org.antlr.v4.parse.GrammarASTAdaptor;
import org.antlr.v4.parse.LeftRecursiveRuleWalker;
import org.antlr.v4.runtime.misc.IntervalSet;
import org.antlr.v4.runtime.misc.Pair;
import org.antlr.v4.tool.ErrorType;
import org.antlr.v4.tool.ast.AltAST;
import org.antlr.v4.tool.ast.GrammarAST;
import org.antlr.v4.tool.ast.GrammarASTWithOptions;
import org.antlr.v4.tool.ast.RuleRefAST;
import org.stringtemplate.v4.ST;
import org.stringtemplate.v4.STGroup;
import org.stringtemplate.v4.STGroupFile;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
/** Using a tree walker on the rules, determine if a rule is directly left-recursive and if it follows
* our pattern.
*/
public class LeftRecursiveRuleAnalyzer extends LeftRecursiveRuleWalker {
public static enum ASSOC { left, right }
public Tool tool;
public String ruleName;
public LinkedHashMap binaryAlts = new LinkedHashMap();
public LinkedHashMap ternaryAlts = new LinkedHashMap();
public LinkedHashMap suffixAlts = new LinkedHashMap();
public List prefixAndOtherAlts = new ArrayList();
/** Pointer to ID node of ^(= ID element) */
public List> leftRecursiveRuleRefLabels =
new ArrayList>();
/** Tokens from which rule AST comes from */
public final TokenStream tokenStream;
public GrammarAST retvals;
public STGroup recRuleTemplates;
public STGroup codegenTemplates;
public String language;
public Map altAssociativity = new HashMap();
public LeftRecursiveRuleAnalyzer(GrammarAST ruleAST,
Tool tool, String ruleName, String language)
{
super(new CommonTreeNodeStream(new GrammarASTAdaptor(ruleAST.token.getInputStream()), ruleAST));
this.tool = tool;
this.ruleName = ruleName;
this.language = language;
this.tokenStream = ruleAST.g.tokenStream;
if (this.tokenStream == null) {
throw new NullPointerException("grammar must have a token stream");
}
loadPrecRuleTemplates();
}
public void loadPrecRuleTemplates() {
String templateGroupFile = "org/antlr/v4/tool/templates/LeftRecursiveRules.stg";
recRuleTemplates = new STGroupFile(templateGroupFile);
if ( !recRuleTemplates.isDefined("recRule") ) {
tool.errMgr.toolError(ErrorType.MISSING_CODE_GEN_TEMPLATES, "LeftRecursiveRules");
}
// use codegen to get correct language templates; that's it though
CodeGenerator gen = new CodeGenerator(tool, null, language);
codegenTemplates = gen.getTemplates();
}
@Override
public void setReturnValues(GrammarAST t) {
retvals = t;
}
@Override
public void setAltAssoc(AltAST t, int alt) {
ASSOC assoc = ASSOC.left;
if ( t.getOptions()!=null ) {
String a = t.getOptionString("assoc");
if ( a!=null ) {
if ( a.equals(ASSOC.right.toString()) ) {
assoc = ASSOC.right;
}
else if ( a.equals(ASSOC.left.toString()) ) {
assoc = ASSOC.left;
}
else {
tool.errMgr.grammarError(ErrorType.ILLEGAL_OPTION_VALUE, t.g.fileName, t.getOptionAST("assoc").getToken(), "assoc", assoc);
}
}
}
if ( altAssociativity.get(alt)!=null && altAssociativity.get(alt)!=assoc ) {
tool.errMgr.toolError(ErrorType.INTERNAL_ERROR, "all operators of alt " + alt + " of left-recursive rule must have same associativity");
}
altAssociativity.put(alt, assoc);
// System.out.println("setAltAssoc: op " + alt + ": " + t.getText()+", assoc="+assoc);
}
@Override
public void binaryAlt(AltAST originalAltTree, int alt) {
AltAST altTree = (AltAST)originalAltTree.dupTree();
String altLabel = altTree.altLabel!=null ? altTree.altLabel.getText() : null;
String label = null;
boolean isListLabel = false;
GrammarAST lrlabel = stripLeftRecursion(altTree);
if ( lrlabel!=null ) {
label = lrlabel.getText();
isListLabel = lrlabel.getParent().getType() == PLUS_ASSIGN;
leftRecursiveRuleRefLabels.add(new Pair(lrlabel,altLabel));
}
stripAltLabel(altTree);
// rewrite e to be e_[rec_arg]
int nextPrec = nextPrecedence(alt);
altTree = addPrecedenceArgToRules(altTree, nextPrec);
stripAltLabel(altTree);
String altText = text(altTree);
altText = altText.trim();
LeftRecursiveRuleAltInfo a =
new LeftRecursiveRuleAltInfo(alt, altText, label, altLabel, isListLabel, originalAltTree);
a.nextPrec = nextPrec;
binaryAlts.put(alt, a);
//System.out.println("binaryAlt " + alt + ": " + altText + ", rewrite=" + rewriteText);
}
@Override
public void prefixAlt(AltAST originalAltTree, int alt) {
AltAST altTree = (AltAST)originalAltTree.dupTree();
stripAltLabel(altTree);
int nextPrec = precedence(alt);
// rewrite e to be e_[prec]
altTree = addPrecedenceArgToRules(altTree, nextPrec);
String altText = text(altTree);
altText = altText.trim();
String altLabel = altTree.altLabel!=null ? altTree.altLabel.getText() : null;
LeftRecursiveRuleAltInfo a =
new LeftRecursiveRuleAltInfo(alt, altText, null, altLabel, false, originalAltTree);
a.nextPrec = nextPrec;
prefixAndOtherAlts.add(a);
//System.out.println("prefixAlt " + alt + ": " + altText + ", rewrite=" + rewriteText);
}
@Override
public void suffixAlt(AltAST originalAltTree, int alt) {
AltAST altTree = (AltAST)originalAltTree.dupTree();
String altLabel = altTree.altLabel!=null ? altTree.altLabel.getText() : null;
String label = null;
boolean isListLabel = false;
GrammarAST lrlabel = stripLeftRecursion(altTree);
if ( lrlabel!=null ) {
label = lrlabel.getText();
isListLabel = lrlabel.getParent().getType() == PLUS_ASSIGN;
leftRecursiveRuleRefLabels.add(new Pair(lrlabel,altLabel));
}
stripAltLabel(altTree);
String altText = text(altTree);
altText = altText.trim();
LeftRecursiveRuleAltInfo a =
new LeftRecursiveRuleAltInfo(alt, altText, label, altLabel, isListLabel, originalAltTree);
suffixAlts.put(alt, a);
// System.out.println("suffixAlt " + alt + ": " + altText + ", rewrite=" + rewriteText);
}
@Override
public void otherAlt(AltAST originalAltTree, int alt) {
AltAST altTree = (AltAST)originalAltTree.dupTree();
stripAltLabel(altTree);
String altText = text(altTree);
String altLabel = altTree.altLabel!=null ? altTree.altLabel.getText() : null;
LeftRecursiveRuleAltInfo a =
new LeftRecursiveRuleAltInfo(alt, altText, null, altLabel, false, originalAltTree);
// We keep other alts with prefix alts since they are all added to the start of the generated rule, and
// we want to retain any prior ordering between them
prefixAndOtherAlts.add(a);
// System.out.println("otherAlt " + alt + ": " + altText);
}
// --------- get transformed rules ----------------
public String getArtificialOpPrecRule() {
ST ruleST = recRuleTemplates.getInstanceOf("recRule");
ruleST.add("ruleName", ruleName);
ST ruleArgST = codegenTemplates.getInstanceOf("recRuleArg");
ruleST.add("argName", ruleArgST);
ST setResultST = codegenTemplates.getInstanceOf("recRuleSetResultAction");
ruleST.add("setResultAction", setResultST);
ruleST.add("userRetvals", retvals);
LinkedHashMap opPrecRuleAlts = new LinkedHashMap();
opPrecRuleAlts.putAll(binaryAlts);
opPrecRuleAlts.putAll(ternaryAlts);
opPrecRuleAlts.putAll(suffixAlts);
for (int alt : opPrecRuleAlts.keySet()) {
LeftRecursiveRuleAltInfo altInfo = opPrecRuleAlts.get(alt);
ST altST = recRuleTemplates.getInstanceOf("recRuleAlt");
ST predST = codegenTemplates.getInstanceOf("recRuleAltPredicate");
predST.add("opPrec", precedence(alt));
predST.add("ruleName", ruleName);
altST.add("pred", predST);
altST.add("alt", altInfo);
altST.add("precOption", LeftRecursiveRuleTransformer.PRECEDENCE_OPTION_NAME);
altST.add("opPrec", precedence(alt));
ruleST.add("opAlts", altST);
}
ruleST.add("primaryAlts", prefixAndOtherAlts);
tool.log("left-recursion", ruleST.render());
return ruleST.render();
}
public AltAST addPrecedenceArgToRules(AltAST t, int prec) {
if ( t==null ) return null;
// get all top-level rule refs from ALT
List outerAltRuleRefs = t.getNodesWithTypePreorderDFS(IntervalSet.of(RULE_REF));
for (GrammarAST x : outerAltRuleRefs) {
RuleRefAST rref = (RuleRefAST)x;
boolean recursive = rref.getText().equals(ruleName);
boolean rightmost = rref == outerAltRuleRefs.get(outerAltRuleRefs.size()-1);
if ( recursive && rightmost ) {
GrammarAST dummyValueNode = new GrammarAST(new CommonToken(ANTLRParser.INT, ""+prec));
rref.setOption(LeftRecursiveRuleTransformer.PRECEDENCE_OPTION_NAME, dummyValueNode);
}
}
return t;
}
/**
* Match (RULE RULE_REF (BLOCK (ALT .*) (ALT RULE_REF[self] .*) (ALT .*)))
* Match (RULE RULE_REF (BLOCK (ALT .*) (ALT (ASSIGN ID RULE_REF[self]) .*) (ALT .*)))
*/
public static boolean hasImmediateRecursiveRuleRefs(GrammarAST t, String ruleName) {
if ( t==null ) return false;
GrammarAST blk = (GrammarAST)t.getFirstChildWithType(BLOCK);
if ( blk==null ) return false;
int n = blk.getChildren().size();
for (int i = 0; i < n; i++) {
GrammarAST alt = (GrammarAST)blk.getChildren().get(i);
Tree first = alt.getChild(0);
if ( first==null ) continue;
if (first.getType() == ELEMENT_OPTIONS) {
first = alt.getChild(1);
if (first == null) {
continue;
}
}
if ( first.getType()==RULE_REF && first.getText().equals(ruleName) ) return true;
Tree rref = first.getChild(1);
if ( rref!=null && rref.getType()==RULE_REF && rref.getText().equals(ruleName) ) return true;
}
return false;
}
// TODO: this strips the tree properly, but since text()
// uses the start of stop token index and gets text from that
// ineffectively ignores this routine.
public GrammarAST stripLeftRecursion(GrammarAST altAST) {
GrammarAST lrlabel=null;
GrammarAST first = (GrammarAST)altAST.getChild(0);
int leftRecurRuleIndex = 0;
if ( first.getType() == ELEMENT_OPTIONS ) {
first = (GrammarAST)altAST.getChild(1);
leftRecurRuleIndex = 1;
}
Tree rref = first.getChild(1); // if label=rule
if ( (first.getType()==RULE_REF && first.getText().equals(ruleName)) ||
(rref!=null && rref.getType()==RULE_REF && rref.getText().equals(ruleName)) )
{
if ( first.getType()==ASSIGN || first.getType()==PLUS_ASSIGN ) lrlabel = (GrammarAST)first.getChild(0);
// remove rule ref (first child unless options present)
altAST.deleteChild(leftRecurRuleIndex);
// reset index so it prints properly (sets token range of
// ALT to start to right of left recur rule we deleted)
GrammarAST newFirstChild = (GrammarAST)altAST.getChild(leftRecurRuleIndex);
altAST.setTokenStartIndex(newFirstChild.getTokenStartIndex());
}
return lrlabel;
}
/** Strip last 2 tokens if → label; alter indexes in altAST */
public void stripAltLabel(GrammarAST altAST) {
int start = altAST.getTokenStartIndex();
int stop = altAST.getTokenStopIndex();
// find =>
for (int i=stop; i>=start; i--) {
if ( tokenStream.get(i).getType()==POUND ) {
altAST.setTokenStopIndex(i-1);
return;
}
}
}
public String text(GrammarAST t) {
if ( t==null ) return "";
int tokenStartIndex = t.getTokenStartIndex();
int tokenStopIndex = t.getTokenStopIndex();
// ignore tokens from existing option subtrees like:
// (ELEMENT_OPTIONS (= assoc right))
//
// element options are added back according to the values in the map
// returned by getOptions().
IntervalSet ignore = new IntervalSet();
List optionsSubTrees = t.getNodesWithType(ELEMENT_OPTIONS);
for (GrammarAST sub : optionsSubTrees) {
ignore.add(sub.getTokenStartIndex(), sub.getTokenStopIndex());
}
// Individual labels appear as RULE_REF or TOKEN_REF tokens in the tree,
// but do not support the ELEMENT_OPTIONS syntax. Make sure to not try
// and add the tokenIndex option when writing these tokens.
IntervalSet noOptions = new IntervalSet();
List labeledSubTrees = t.getNodesWithType(new IntervalSet(ASSIGN,PLUS_ASSIGN));
for (GrammarAST sub : labeledSubTrees) {
noOptions.add(sub.getChild(0).getTokenStartIndex());
}
StringBuilder buf = new StringBuilder();
int i=tokenStartIndex;
while ( i<=tokenStopIndex ) {
if ( ignore.contains(i) ) {
i++;
continue;
}
Token tok = tokenStream.get(i);
// Compute/hold any element options
StringBuilder elementOptions = new StringBuilder();
if (!noOptions.contains(i)) {
GrammarAST node = t.getNodeWithTokenIndex(tok.getTokenIndex());
if ( node!=null &&
(tok.getType()==TOKEN_REF ||
tok.getType()==STRING_LITERAL ||
tok.getType()==RULE_REF) )
{
elementOptions.append("tokenIndex=").append(tok.getTokenIndex());
}
if ( node instanceof GrammarASTWithOptions ) {
GrammarASTWithOptions o = (GrammarASTWithOptions)node;
for (Map.Entry entry : o.getOptions().entrySet()) {
if (elementOptions.length() > 0) {
elementOptions.append(',');
}
elementOptions.append(entry.getKey());
elementOptions.append('=');
elementOptions.append(entry.getValue().getText());
}
}
}
buf.append(tok.getText()); // add actual text of the current token to the rewritten alternative
i++; // move to the next token
// Are there args on a rule?
if ( tok.getType()==RULE_REF && i<=tokenStopIndex && tokenStream.get(i).getType()==ARG_ACTION ) {
buf.append('['+tokenStream.get(i).getText()+']');
i++;
}
// now that we have the actual element, we can add the options.
if (elementOptions.length() > 0) {
buf.append('<').append(elementOptions).append('>');
}
}
return buf.toString();
}
public int precedence(int alt) {
return numAlts-alt+1;
}
// Assumes left assoc
public int nextPrecedence(int alt) {
int p = precedence(alt);
if ( altAssociativity.get(alt)==ASSOC.right ) return p;
return p+1;
}
@Override
public String toString() {
return "PrecRuleOperatorCollector{" +
"binaryAlts=" + binaryAlts +
", ternaryAlts=" + ternaryAlts +
", suffixAlts=" + suffixAlts +
", prefixAndOtherAlts=" +prefixAndOtherAlts+
'}';
}
}
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