165. PhantomData — The Zero-Sized Marker That Pretends to Own a T

Wed, 27 May 2026 09:00:00 +0100

You write a generic struct, never actually store a T in any field, and the compiler stops you with “parameter T is never used”. PhantomData<T> is the zero-cost lie that fixes it — a marker that occupies no bytes but tells the compiler “act as if I own a T.”

Phantom-Data on rustbites

165. PhantomData — The Zero-Sized Marker That Pretends to Own a T