[TypeScript] SyntaxError on array destructuring

## Bug Report

**Current Behavior**
SyntaxError: Unexpected type cast in parameter position

**Input Code**
```js
[x as Foo] = arr
```

**Expected behavior/code**
no error

**Babel Configuration (.babelrc, package.json, cli command)**
@babel/parser with typescript plugin

**Environment**
- Babel version(s): 7.4.5
- Node/npm version: Node 11.13 / npm 6.7