question: private Token toPrefixToken ( ILeafNode leaf ) { Lexer lexer = new InternalN4JSLexer ( ) ; String text = leaf . getText ( ) ; String prefix = text . substring ( 0 , endOffset - leaf . getTotalOffset ( ) ) ; ANTLRStringStream stream = new ANTLRStringStream ( prefix ) ; lexer . setCharStream ( stream ) ; Token nextToken = lexer . nextToken ( ) ; return new CommonToken ( nextToken . getType ( ) , nextToken . getText ( ) ) ; }
target:  Produce an Antlr token for the prefix of the given leaf that overlaps the requested region