Lexer hack

In computer programming, the lexer hack is a solution to parsing context-sensitive grammars such as C, where classifying a sequence of characters as a variable name or a type name requires contextual information, by feeding contextual information backwards from the parser to the lexer.

Lexer hack is frowned upon in modern compilers as it creates tight coupling between otherwise largely independent steps in the compilation process. Instead, identifier-like tokens are tokenized as identifiers and later disambiguated by the parser, allowing cleaner separation of concerns.