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Note-rustc-hacking-guide---front-end.md

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+The compiler front-end includes the lexer, parser and syntax extensions (macros), among other things. The front-end is in a separate crate, called ```syntax```, whose source files live in the ```src/librustsyntax``` directory under the main Rust source tree. (The middle and back end are in ```src/rustc```.)
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+## Adding a new keyword
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+If you need to add a new keyword to Rust (a rare occurrence, with hope!) edit one or the other of the functions ```contextual_keyword_table``` or ```restricted_keyword_table``` in ```src/librustsyntax/parse/token.rs```. Together, these functions construct the table that parser functions consult when determining which identifiers are keywords.