function getAllExpressionStatements(node) {
  assert(node.body && node.body.body);
  const expressionStatements = [];
  for (const childNode of node.body.body) {
    if (childNode.type == 'ExpressionStatement') {
      expressionStatements.push(childNode);
    } else if (childNode.body) {
      const childExpressions = getAllExpressionStatements(childNode);
      expressionStatements.push(...childExpressions);
    }
  }
  return expressionStatements;
}
Recursively find all expression statements in all block nodes.
@param {ASTNode} node
@return {!Array<ASTNode>}