Abstract: A matching library of a code analysis system defines a number of predicates applicable to an abstract syntax tree (AST) corresponding to program code being analyzed. The predicates represent whether or not nodes of the program code's AST have corresponding properties, such as representing a class that inherits from another given class. The code analysis system obtains an AST to analyze, a predicate expression query that includes predicates of the matching library, and action code. The code analysis system identifies nodes of the AST that match the predicate expression query by executing code of the matching library and executes the action code against the identified nodes.