Inconsistent behaviour between double and triple equals

[augusto-altman]

Flow version: v0.117.1

Expected behavior

It consistently fails when comparing a number and a string.

Actual behavior

The current behavior is absolutely inconsistent, mainly between the behavior of double and triple equals comparison, but it is also inconsistent when using triple equals against a number literal. See the following cases:

• When doing someNumber == someString it fails with the message Cannot compare string [1] to number [2].

• When doing someNumber === someString it doesn't fail at all.

• When doing if(someString === 3) it fails with the message number literal 3 [1] is incompatible with string [2].

• When doing console.log(someString === 3) it doesn't fail at all.

• When doing if(someString === someNumber) and console.log(someString === someNumber) it doesn't fail at all.

• Link to Try-Flow or Github repo: reproduce it here

I consider this is especially important due to the following two facts:

1. Type refinements require triple equals. See this issue
2. The behavior is solid and consistent in Typescript. See this equivalent playground