Bug Report

Current Behavior
In specific cases, code containing a bigint type-annotation does not want to compile.

Input Code

• REPL

const {result} = idArray.reduce(
  (a, b) => {},
  {result: [] as (number | bigint)[]},
)

Expected behavior/code
A clear and concise description of what you expected to happen (or code).

Babel Configuration (.babelrc, package.json, cli command)

{
  presets: [
    '@babel/preset-env',
    '@babel/preset-typescript',
  ],
  plugins: [
    '@babel/plugin-syntax-bigint',
  ],
}

Environment

• Babel version(s): v7.5.5
• Node/npm version: Node 12
• OS: macOS 10.14.6
• Monorepo: n/a
• How you are using Babel: doesn't matter