consider giving MutatorPlugins some state for statistics and profiling.

[bttmly]

// current:
const plugin: MutatorPlugin = {
  type: "mutator",
  name: "tweak-arguments",
  nodeTypes: [S.CallExpression],
  filter: util.lengthAtPropGreaterThan("arguments", 0),
  mutator: util.dropEachOfProp("arguments"),
};
// next:
export default new MutatorPlugin({
  name: "tweak-arguments",
  nodeTypes: [S.CallExpression],
  filter: util.lengthAtPropGreaterThan("arguments", 0),
  mutator: util.dropEachOfProp("arguments"),
})

what this allows is the mutator to carry some state around and do things like track how many times each gets called, how expensive its mutations are, etc.