Function eval_pred 

pub fn eval_pred<C: PredContext>(ir: &SemIr, expr: ExprId, ctx: &mut C) -> bool

Evaluates a predicate expression to its truthiness.

This is the runtime entry point for semantic predicate transitions; it is side-effect-free except for PExpr::Hook nodes, whose implementations own their replay-safety (they may run repeatedly on speculative paths).