Order of expressions in if block affect type narrowing from unknown

[frederickfogerty]

TypeScript Version: 3.7-Beta

Search Terms: object null order type narrowing

Code

const maybeObject: unknown = {};

if (maybeObject != null && typeof maybeObject === 'object') {
    Object.keys(maybeObject)
}

if (typeof maybeObject === 'object' && maybeObject != null) {
    Object.keys(maybeObject)
}

Playground link

Expected behavior:

No type errors; maybeObject is correctly narrowed to object in both cases.

Actual behavior:

The first if block throws an error as maybeObject is incorrectly narrowed to object | null, whereas the second maybeObject is incorrectly narrowed.

No overload matches this call.
  Overload 1 of 2, '(o: {}): string[]', gave the following error.
    Argument of type 'object | null' is not assignable to parameter of type '{}'.
      Type 'null' is not assignable to type '{}'.
  Overload 2 of 2, '(o: object): string[]', gave the following error.
    Argument of type 'object | null' is not assignable to parameter of type 'object'.
      Type 'null' is not assignable to type 'object'.(2769)

Playground Link: http://www.typescriptlang.org/play/?ts=3.7-Beta&ssl=1&ssc=1&pln=9&pc=2#code/MYewdgzgLgBAtgQwJ4CMCmB5FArNwoBcMArmANZggDuYMAvDAN4C+A3AFDsCWAZjABSJUmHHlgBCBmGIAbGTABkCmFCQAHNCD5D0WXPnp0GAchCj8xgJRN2MOzD1iAdGTRIIg5LvNRL7Zpy8AqoaWvBeIvqwRiZmUcaKyjqRYjCSMNJy1oy29o74Lm4eyfm+-kA

Related Issues: No

[jack-williams]

Duplicate of #28131

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.