Macro syn::map

macro_rules! map {
    ($i:expr, $submac:ident!( $($args:tt)* ), $g:expr) => { ... };
    ($i:expr, $f:expr, $g:expr) => { ... };
}

Transform the result of a parser by applying a function or closure.

• Syntax: map!(THING, FN)
• Output: the return type of function FN applied to THING

#[macro_use]
extern crate syn;

use syn::{Expr, ExprIf};

/// Extracts the branch condition of an `if`-expression.
fn get_cond(if_: ExprIf) -> Expr {
    *if_.cond
}

/// Parses a full `if`-expression but returns the condition part only.
///
/// Example: `if x > 0xFF { "big" } else { "small" }`
/// The return would be the expression `x > 0xFF`.
named!(if_condition -> Expr,
    map!(syn!(ExprIf), get_cond)
);

/// Equivalent using a closure.
named!(if_condition2 -> Expr,
    map!(syn!(ExprIf), |if_| *if_.cond)
);

This macro is available if Syn is built with the "parsing" feature.