A syntax tree analyzer registers action callbacks to analyze the syntax/grammar for the source file and reports pure syntactic issues. For example, a missing semicolon at the end of a statement is a syntactic error, while assigning an incompatible type to a symbol with no possible type conversion is a semantic error.

In this section, we will write a syntax tree analyzer that analyzes all the statements in a source file and generates a syntax warning for any statement that is not enclosed in a block, that is curly braces { and }. For example, the following code will generate a warning for both the if statement and the System.Console.WriteLine invocation statement, but the while statement is not flagged:

void Method()
{
 while (...)
  if (...)
   System.Console.WriteLine(value);
}