Warn if lookahead is too big in matchTokenStreamPredicate()

compiler/frontend/src/org/jetbrains/jet/lang/parsing/AbstractJetParsing.java

@@ -17,6 +17,8 @@
 package org.jetbrains.jet.lang.parsing;
 
 import com.intellij.lang.PsiBuilder;
+import com.intellij.openapi.application.ApplicationManager;
+import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.tree.TokenSet;
 import com.intellij.util.containers.Stack;
@@ -31,7 +33,11 @@ import java.util.Map;
 import static org.jetbrains.jet.lexer.JetTokens.*;
 
 /*package*/ abstract class AbstractJetParsing {
+    private static final Logger LOGGER = Logger.getInstance(AbstractJetParsing.class);
+    private static final int LOOK_AHEAD_SIZE_WARN = 1000;
+
     private static final Map<String, JetKeywordToken> SOFT_KEYWORD_TEXTS = new HashMap<String, JetKeywordToken>();
+
     static {
         for (IElementType type : JetTokens.SOFT_KEYWORDS.getTypes()) {
             JetKeywordToken keywordToken = (JetKeywordToken) type;
@@ -309,6 +315,7 @@ import static org.jetbrains.jet.lexer.JetTokens.*;
 
     protected int matchTokenStreamPredicate(TokenStreamPattern pattern) {
         PsiBuilder.Marker currentPosition = mark();
+        int beginOffset = myBuilder.getCurrentOffset();
         Stack<IElementType> opens = new Stack<IElementType>();
         int openAngleBrackets = 0;
         int openBraces = 0;
@@ -355,7 +362,19 @@ import static org.jetbrains.jet.lexer.JetTokens.*;
             }
             advance(); // skip token
         }
+        int endOffset = myBuilder.getCurrentOffset();
+
         currentPosition.rollbackTo();
+
+        if (endOffset - beginOffset > LOOK_AHEAD_SIZE_WARN && !ApplicationManager.getApplication().isHeadlessEnvironment()) {
+            String text = new StringBuilder(myBuilder.getOriginalText())
+                    .insert(endOffset, "<~~!END!~~>")
+                    .insert(beginOffset, "<~~!BEGIN!~~>")
+                    .toString();
+
+            LOGGER.warn("Suspicious big range: \n" + text);
+        }
+
         return pattern.result();
     }