invokedOnTheSpot

({ body })() — the body of a lambda, as in run { }, invoked on the spot. A lambda is a root for the data-flow analysis: what decides whether a var a closure writes may still smart-cast. A property initializer is no root, so it would let such a smart cast through; the anonymous initializer the body arrives in is one, but fir2ir flattens it into the script's top level, where every local variable becomes a property. The backend inlines a lambda invoked on the spot, so the body still runs straight in the constructor.