Macro invocation syntax

Decided

D-0009, settled by the language’s author: part of spec §18. Older text cites it as 18.9.

The macro’s kind decides its spelling (r65, by the user; r63 had made it #name everywhere, and before that it was #name … for declarations and name!(…) for expressions). An expr or stmt macro reads like the call it stands for: max!(a, b), log!("warn", "…", hp), one bracketed group — an expr macro wherever an expression may be, a stmt macro as a whole statement. A decl macro reads like the declaration it writes: #machine Foo(…) { … }, running to the end of the line. A dependency’s is dep::max!(…) or #dep::machine …. The formatting macros are println!(…); the other intrinsics, which stand for a value, stay #file, #location, #expr_text(e). Each macro has one spelling, and the other is an error saying which to write (DZ0610, and DZ0217 for an intrinsic). The user’s reason: #println() and machine!/location!() both read wrong — ! is for what looks like a function, and a log looks like one. ! after a name cannot be read as “not” or as !-> (§12.5, §12.7, §12.8)