p_enemy: A_VileTarget reproduces vanilla Doom bug passing x for y argument #132

Context

A_VileTarget in room/src/doom/p_enemy.rs spawns the Archvile's fire object.

Behavior

The Rust port faithfully reproduces a vanilla Doom bug from p_enemy.c: actor->target->x is passed as the Y argument to P_SpawnMobj instead of actor->target->y:

let fog: *mut mobj_t = P_SpawnMobj(
    (*(*actor).target).x,
    (*(*actor).target).x,  // <-- should be .y in a fixed engine
    (*(*actor).target).z,
    MT_FIRE,
);

This is intentional for demo compatibility - vanilla demos depend on the buggy spawn position.

Location

room/src/doom/p_enemy.rs:1484 (flagged with // FIXME:).

Decision needed

Track whether the Rust port should:

• keep the bug verbatim for demo compatibility (current behavior, no action), or
• gate the fix behind a non-vanilla compat flag.

This issue tracks the divergence point; no fix is required if vanilla-faithful behavior is the project goal.