doKeyword

Explanation

do has been reserved since the 2015 edition, as part of the Rust Reference's original reserved-keyword list. There is no strong, publicly documented direction for what it will eventually become. The most commonly guessed future is some form of a do-while loop (a loop that runs its body once before checking the condition, as in C and several other languages) — Rust today has no such form; loop { ... } with a manual break is the closest equivalent. Be honest that this is speculative: no active RFC is attached to do, and it may simply remain unclaimed indefinitely.

Using do as an ordinary identifier is a compile error today. The raw-identifier form r#do is legal, the same escape hatch every reserved keyword offers.

Usage examples

Using the raw-identifier escape hatch

let do = 5;     // error: expected identifier, found reserved keyword `do`
let r#do = 5;   // ok: the raw-identifier form escapes the reservation

Explanation

Embedded support: Full

Full support. Keyword reservation is a lexer-level fact, identical in #![no_std] and hosted Rust alike — do carries no defined meaning on any target, so there's no embedded-specific behavior to describe.

Usage examples

The `do` reservation, unaffected by target

let do = 5;     // error: expected identifier, found reserved keyword `do`, on every target
let r#do = 5;   // ok: the raw-identifier form escapes the reservation, on every target