Macro timed 

macro_rules! timed {
    ($label:expr, $callback:expr, $block:expr) => { ... };
}

Times the execution of a block and invokes a callback with the label and elapsed duration.

In debug builds (debug_assertions enabled), this macro:

1. Records the start time
2. Executes the block
3. Calculates elapsed time
4. Calls the callback with (label, duration)
5. Returns the block’s result

In release builds, the timing is completely eliminated — only the block executes, with zero overhead.

Arguments

• $label - A label (any type accepted by the callback) identifying what is being timed
• $callback - A closure or function: FnOnce(label, Duration)
• $block - The code block to time

Examples

use varvedb::timed;
use std::time::Duration;

let result = timed!("my_operation", |label, dur: Duration| {
    eprintln!("[{label}] took {dur:?}");
}, {
    // expensive work here
    42
});
assert_eq!(result, 42);

Using a named function as callback:

fn log_timing(label: &str, duration: std::time::Duration) {
    eprintln!("[timing] {}: {:?}", label, duration);
}

let value = timed!("computation", log_timing, {
    (0..1000).sum::<i32>()
});