Reserved Syntax

The lexer and grammar reserve the following forms because the language plans to use them. The compiler does not yet lower them; using them today either errors at parse time or is silently ignored by later passes. Treat this list as a roadmap, not as features.

Reserved	Status
Raw strings `r"..."`	Reserved. Will treat backslashes literally (no escape processing). Today an `r` prefix lexes as a separate identifier followed by an ordinary string literal.
Escapes `\a` `\b` `\f` `\v`	Reserved. The lexer does not yet recognise them; they pass through as a literal backslash plus the following character. The implemented escapes are `\n` `\t` `\r` `\0` `\\` `\'` `\"` `\xHH`.
`yield`	Parser accepts a `yield` expression; no generator semantics exist. `async` / `await` are fully implemented - see section 19.
Optional chaining `?.`	Token reserved; not consumed by the parser.
Spread `...` in calls / literals	The token exists for variadic parameter declarations only.
Pure-virtual class method (e.g. `= 0` syntax)	Not implemented. Use a `virtual` method without a body to declare an interface point.
Macros	No macro system exists, and `macro` is not currently a reserved word (it lexes as an ordinary identifier). A future hygienic macro system may introduce one.
`![pure]`	Reserved. Will assert the function has no observable side effects (enabling aggressive folding). Parsed as an unknown directive today (warning + no semantics).
`![const]`	Reserved. Will mark a function as evaluable at compile time.
`![noreturn]`	Reserved. Will declare a function that never returns normally.
`![constructor]` / `![destructor]`	Reserved. Will register functions that run before `main` / after `main` returns.
`![repr(<int_type>)]` on enums	Reserved. Use `type enum Foo : u8 { ... }` syntax for now; future versions may accept `![repr(u8)]` as an equivalent spelling.
`![derive(Trait, ...)]`	Reserved. The directive's argument list is parsed and validated (an unknown trait name is rejected), but nothing consumes it: no implementation is synthesized for any listed trait. `Copy` in particular is decided structurally, not declared - see section 16.

When any of these moves out of "reserved" and into "implemented," it will be added to the relevant section of this document and removed from this table.