Sealed object properties not checked in conditionals

[kevanstannard]

Is it correct that sealed object properties are not checked in conditional statements?

For example:

// Create a sealed object
const o = {
  Foo: 'Foo',
};

// Reports an Error
const fooz = o.Fooz;

// Reports an Error
const x = o.Fooz === 'Bar';

// Does not report an error
if (o.Fooz === 'Bar') {}

// Does not report an error
const y = (o.Fooz === 'Bar') ? true : false;

Edit: Added some more examples. It looks like intermediate expressions (the if statement and the ternary) do not have the type check applied.

[popham]

Non-existence is not an error within a conditional expression. See the comment from

flow/src/typing/statement.ml

Lines 4453 to 4456 in c9131da

	(* Conditional expressions are checked like expressions, except that property
	accesses are provisionally allowed even when such properties do not exist.
	This accommodates the common JavaScript idiom of testing for the existence
	of a property before using that property. *)

[kevanstannard]

@popham many thanks for clarifying.