Spec §A — Appendix

A.1 Operator precedence

Tightest to loosest; binary levels are left-associative (§3.7):

Above level 12 sit the expression forms (closures, blocks, if, match, for, let, ret, assignment), and above those the top-tier-only forms: const expr and struct initializers (§3.8).

A.2 Reserved words

async     await     const    css     else    enum    export
external  for       fun      if      impl    import  in
is        let       macro    match   mod     mut     null
ret       struct    trait    type    use     true    false

Contextual keywords (an identifier everywhere but their one position; B414 made with, borrows, own, dyn, lazy and jump contextual, and B459 added then, B570 auto):

as        auto      borrows   context   dyn       jump      lazy
only      own       self      Self      sync      then      void
with

Also matched by text in one position: break/continue (after jump), and the attribute names derive service client_service extern must_use track_caller rpc trait_only doc expose platform deprecated internal resource hint reactive (resource was a keyword until B413 made it the [resource] attribute).

A.3 Literal suffixes

i8 i16 i32 i53 u8 u16 u32 u53 usize f f32 f64 n: §2.3 (unknown suffixes error; i64/u64 were renamed to i53/u53). Unsuffixed: integer → i32, fractional → f64.

A.4 Lang items

Std declarations the language itself depends on:

The prelude column says whether the default (base) prelude makes the name ambient too — Option is both a lang item and a prelude member, and that is where the two ideas meet (§4.7). built-in means the language has it with no prelude at all.