Appendix B — Keywords and contextual identifiers

See §3.6 and §3.7 for the normative definitions.

B.1 Reserved words

These 43 words are reserved; none may be used as an identifier.

and     bool    break   bytes   continue elif    else    enum
f32     false   float   fn      for      handle  i8      i16
i32     i64     if      in      inout    int     is      match
not     null    or      or_else  or_return parallel ptr  return
select  soa     spawn   string  struct   true    type    u8
u16     u32     u64

42 of the 43 are lexer keywords: the set is exactly keyword(), which never hands back an identifier token for one. soa is the exception — it lexes as an ordinary identifier and is reserved by the parser, which requires a [ after it in every expression position . The difference is invisible to a program and shows only in the diagnostic: soa := 5 is accepted at its declaration, and the next mention of the name dies with expected '[' after soa, so the binding is declarable and permanently unusable. It is listed here, with the reserved words, because that is what it costs a program — not under B.2, where it sat until 2026-09-02 under a heading promising the opposite.

is is the variant test, for an enum, an Option or a Result (§19.8). It is reserved, not contextual: no .ty file in this tree used is as an identifier when it was added, so reserving it broke nothing, and an operator keyword shares its position with an ordinary name (x is y) in a way that pass, a whole statement, does not.

Of these, the type keywords are int, float, bool, string, ptr, bytes, the fixed-width integers u8, u16, u32, u64, i8, i16, i32, i64, and f32. There is no while, char, or void keyword.

B.2 Contextual identifiers

Significant only in a specific position; ordinary identifiers elsewhere (a variable of the same name is unaffected).