intermediate

Build the tool: find the watcher that watched a value

Implement this from the stub. Hidden tests grade the behaviour you write, not the comments you leave.

This exercise is real. This platform's Vue track ships a search composable whose original sin was one line: `watch(state.query, …)`. The expression evaluates immediately — to a plain string — and a string carries no subscription, so the watcher never fired. Not once. Vue does log a warning, but a warning at runtime on a code path nobody exercises is a message to no one.

export interface ValueWatcher {
  /** The file the watcher is in, as given. */
  file: string
  /** 1-based line of the watch call. */
  line: number
  /** The member expression that was handed to watch, e.g. "state.query". */
  source: string
}

export interface SourceFile {
  path: string
  contents: string
}

/**
 * Reports every watch() whose first argument is a member expression —
 * a value read once, where a source read every time was needed.
 */
export function findValueWatchers(files: SourceFile[]): ValueWatcher[] {
  // Your implementation here
  return []
}

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