# Annotation Type Fused

@Retention(CLASS) @Target(TYPE) public @interface Fused

Marks a class whose constructor-created primitive-array fields are fully ENCAPSULATED, letting ParparVM allocate each instance TOGETHER with those arrays as a single heap block ("fused object"): one allocation instead of several, one object for the garbage collector instead of several, and the arrays share the owner's cache lines. A fused array keeps a completely ordinary header -- all reading code, `System.arraycopy`, iteration and bounds checks work unchanged -- but it has no independent GC identity: it is never separately tracked, marked for reclamation, or swept; it simply lives and dies with its owner.

The translator fuses a constructor-assigned field when the constructor contains an unconditional `this.f = new T[n]` where `T` is a primitive type and `n` is a constructor parameter or constant (bounds-check guards that throw are fine before it). Constructors keep chaining normally, and every other instantiation path -- reflection, deserialization, oversized arrays that do not fit a fused block -- transparently falls back to ordinary separate allocations with identical semantics.

THE CONTRACT: the marked class must never let a fused array reference escape into another object's field, an array element, or a static that can outlive the instance. Holding it in locals, passing it as a call argument, or copying its contents out is always safe (the VM keeps the whole block alive through any reference into it held on a thread stack). Typical candidates: string/buffer classes owning their `char[]`, image types owning their pixel `int[]`/`byte[]` data.