Macro dev_only 

macro_rules! dev_only {
    ($($body:tt)*) => { ... };
}

Runs body only in a build that compiles in development diagnostics.

Expands to if DEV { body }. Because DEV is a const, a release build folds the branch away and drops body with it, including any message strings and bookkeeping it alone references.

body is type-checked in every mode. That is the point: a diagnostic that only compiles on one profile rots, and the rot surfaces as a broken release build. The cost is that body may not reference items that themselves exist only in a dev build.

Control flow escapes the block on one profile only. A return, ?, break, or continue inside body runs in a dev build and is skipped entirely in a release build, so the surrounding function must be correct when the block does nothing. Confine body to diagnostics and their bookkeeping; if the enclosing function’s result depends on it, the profiles disagree.

Examples

use retroglyph_core::dev_only;

let sprite_px = (32, 32);
let cell_px = (16, 16);

dev_only!({
    if sprite_px > cell_px {
        warn_overflow(sprite_px, cell_px);
    }
});

The block form is not required; any statements work.

dev_only!(misses += 1;);