> parse = require("@typescript-eslint/typescript-estree").parse
[Function: parse]
> ast = parse('class A {a (@d private x: number) {}}')
{
  type: 'Program',
  body: [
    {
      type: 'ClassDeclaration',
      id: [Object],
      body: [Object],
      superClass: null
    }
  ],
  sourceType: 'script'
}
> ast.body[0].body.body[0].value.params[0].decorators[0]
{ type: 'Decorator', expression: { type: 'Identifier', name: 'd' } }
> ast.body[0].body.body[0].value.params[0].parameter.decorators[0]
{ type: 'Decorator', expression: { type: 'Identifier', name: 'd' } }