Syntax validation is roughly equivalent to checking whether text input is grammatically correct (without worrying about the meaning, as opposed to semantic validation). The purpose of syntax validation is to check that the user is entering a valid sequence of tokens. The language parser takes the tokens produced during the lexical analysis stage, and attempts to build an abstract syntax tree (AST) structure to represent that input. The editor reacts to invalid sequences of tokens by displaying annotations and messages: errors, warning, and information.
