TypeScript definitions for babel-types is* checks should accept any type, not just object

[ian-craig]

Bug Report

Current Behavior
Let's use t.isIdentifier as an example.

Current definition generated in packages\babel-types\lib\index.d.ts:

export function isIdentifier(node: object, opts?: object | null): node is Identifier;

Input Code

const func = t.functionDeclaration(...);

if (t.isIdentifier(func.id, { name: 'foo' })) {
  // Do something
}

Expected behavior/code
This code runs perfectly fine, and if func.id === 'foo' the // Do something will be called.

However, in TypeScript with strictNullChecks you get a type error on compile because func.id has type Identifier | null | undefined, and the argument type is object which does not accept null | undefined.

In actual fact, all the is* validate the value passed to it properly, so there is no need to restrict the type.

Babel Configuration (.babelrc, package.json, cli command)
N/A

Environment

• Babel version(s): v7.1.3
• Node/npm version: v10.15.1
• OS: Windows 10
• Monorepo: no
• How you are using Babel: importing - like a plugin would

Possible Solution
Change from object to any type for value of all is* type declarations

I'm happy to submit a PR, should be a very small isolated fix.

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