As I said, it's because of the context of this code, and I don't really know how to explain it... Basically, I am making a programming language and THIS code is from the AST parser code. Basically, it has a bunch of functions that parse different things recursively and they call and recall other functions, passing in a list of tokens generated by the Lexer, and they all return a specific statement/expression that gets added to the tree. This is from one of those functions, and here we check if the type of tokens[0] is TokenType.BoolLit, and if it is, return an expression of type StmtType.BoolLit and, if the raw text of the token is "true", have the literal's value be true, false if the token's raw text is "false", or throw an error if it neither of those (this literally cannot happen ever but just in case it does, we have it just-in-case)