doxygen: document on the main page that we have access to syntax tree, symbol database and library.

cli/main.cpp

@@ -25,10 +25,19 @@
  * @section overview_sec Overview
  * Cppcheck is a simple tool for static analysis of C/C++ code.
  *
- * The method used is to first tokenize the source code and then analyse the token list.
- * In the token list, the tokens are stored in plain text.
+ * When you write a checker you have access to:
+ *  - %Token list = the tokenized code
+ *  - Syntax tree = Syntax tree of each expression
+ *  - SymbolDatabase = Information about all types/variables/functions/etc
+ *    in the current translation unit
+ *  - Library = Information about functions
  *
- * The checks are written in C++. The checks are addons that can be easily added/removed.
+ * Use --debug on the command line to see debug output for the token list
+ * and the syntax tree. If both --debug and --verbose is used, the symbol
+ * database is also written.
+ *
+ * The checks are written in C++. The checks are addons that can be
+ * easily added/removed.
  *
  * @section writing_checks_sec Writing a check
  * Below is a simple example of a check that detect division with zero:
@@ -45,8 +54,9 @@ void CheckOther::checkZeroDivision()
  @endcode
  *
  * The function Token::Match is often used in the checks. Through it
- * you can match tokens against patterns.
- *
+ * you can match tokens against patterns. It is currently not possible
+ * to write match expressions that uses the syntax tree, the symbol database,
+ * nor the library. Only the token list is used.
  *
  * @section checkclass_sec Creating a new check class from scratch
  * %Check classes inherit from the Check class. The Check class specifies the interface that you must use.