For now, this reference is a best-effort document. We strive for validity and completeness, but are not yet there. In the future, the docs and lang teams will work together to figure out how best to do this. Until then, this is a best-effort attempt. If you find something wrong or missing, file an issue or send in a pull request.


      [a-z A-Z] [a-z A-Z 0-9 _]\*
   | _ [a-z A-Z 0-9 _]+

RAW_IDENTIFIER : r# IDENTIFIER_OR_KEYWORD Except crate, extern, self, super, Self

NON_KEYWORD_IDENTIFIER : IDENTIFIER_OR_KEYWORD Except a strict or reserved keyword


An identifier is any nonempty ASCII string of the following form:


  • The first character is a letter.
  • The remaining characters are alphanumeric or _.


  • The first character is _.
  • The identifier is more than one character. _ alone is not an identifier.
  • The remaining characters are alphanumeric or _.

A raw identifier is like a normal identifier, but prefixed by r#. (Note that the r# prefix is not included as part of the actual identifier.) Unlike a normal identifier, a raw identifier may be any strict or reserved keyword except the ones listed above for RAW_IDENTIFIER.