function isSideEffectFree(node) {
			return SIDE_EFFECT_FREE_NODE_TYPES.has(node.type);
		}
Checks if a node is free of side effects.

This check is stricter than it needs to be, in order to keep the implementation simple.
@param {ASTNode} node A node to check.
@returns {boolean} True if the node is known to be side-effect free, false otherwise.