Introduced BackwardsScanner::LA(n). LA(n) returns the n-th lookhead token.

src/libs/cplusplus/BackwardsScanner.cpp

@@ -45,6 +45,8 @@ BackwardsScanner::BackwardsScanner(const QTextCursor &cursor, const QString &suf
         _text += suffix;
 
     _tokens.append(_tokenize(_text, previousBlockState(_block)));
+
+    _startToken = _tokens.size();
 }
 
 int BackwardsScanner::state() const
@@ -53,8 +55,11 @@ int BackwardsScanner::state() const
 const QList<SimpleToken> &BackwardsScanner::tokens() const
 { return _tokens; }
 
-const SimpleToken &BackwardsScanner::operator[](int i) const
-{ return const_cast<BackwardsScanner *>(this)->fetchToken(i); }
+const SimpleToken &BackwardsScanner::LA(int index) const
+{ return const_cast<BackwardsScanner *>(this)->fetchToken(_startToken - index); }
+
+const SimpleToken &BackwardsScanner::operator[](int index) const
+{ return const_cast<BackwardsScanner *>(this)->fetchToken(index); }
 
 const SimpleToken &BackwardsScanner::fetchToken(int i)
 {
@@ -89,7 +94,7 @@ const SimpleToken &BackwardsScanner::fetchToken(int i)
 }
 
 int BackwardsScanner::startToken() const
-{ return _tokens.size(); }
+{ return _startToken; }
 
 int BackwardsScanner::startPosition() const
 { return _block.position(); }

src/libs/cplusplus/BackwardsScanner.h

@@ -54,7 +54,11 @@ public:
     QString text(int begin, int end) const;
     QStringRef textRef(int begin, int end) const;
 
-    const SimpleToken &operator[](int i) const;
+    // 1-based
+    const SimpleToken &LA(int index) const;
+
+    // n-la token is [startToken - n]
+    const SimpleToken &operator[](int index) const; // ### deprecate
 
     int startOfMatchingBrace(int index) const;
     int previousBlockState(const QTextBlock &block) const;
@@ -71,6 +75,7 @@ private:
     QString _text;
     SimpleLexer _tokenize;
     int _maxBlockCount;
+    int _startToken;
 };
 
 } // end of namespace CPlusPlus