Parse a functional macro declaration from a list of tokens.

Returns the identifier for the macro and the argument list (in order). The input should not include #define. The actual definition is not parsed and may be obtained from the unparsed data returned.

Returns an error if the input is not a functional macro or if the token stream contains comments.

Example

use cexpr::expr::{IdentifierParser, EvalResult, fn_macro_declaration};
use cexpr::assert_full_parse;
use cexpr::token::Kind::*;
use cexpr::token::Token;

// #define SUFFIX(arg) arg "suffix"
let tokens = vec![
    (Identifier,  &b"SUFFIX"[..]).into(),
    (Punctuation, &b"("[..]).into(),
    (Identifier,  &b"arg"[..]).into(),
    (Punctuation, &b")"[..]).into(),
    (Identifier,  &b"arg"[..]).into(),
    (Literal,     &br#""suffix""#[..]).into(),
];

// Try to parse the functional part
let (expr, (ident, args)) = fn_macro_declaration(&tokens).unwrap();
assert_eq!(ident, b"SUFFIX");

// Create dummy arguments
let idents = args.into_iter().map(|arg|
    (arg.to_owned(), EvalResult::Str(b"test".to_vec()))
).collect();

// Evaluate the macro
let (_, evaluated) = assert_full_parse(IdentifierParser::new(&idents).expr(expr)).unwrap();
assert_eq!(evaluated, EvalResult::Str(b"testsuffix".to_vec()));