const wrong = () => (1 < 3) as true // type: () => true this should be an error.

[jko206]

🔎 Search Terms

• typescript bug return type true
• () => true bug

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about "typescript bug return type true"

⏯ Playground Link

https://

💻 Code

const wrong = () => (2 < 3) as true

🙁 Actual behavior

This doesn't trigger a TS error.

🙂 Expected behavior

It should.

Additional information about the issue

I know this would be a hard challenge to solve, but I thought you guys should at least know about it.

[dragomirtitian]

Maybe I'm just slow today, but why should this trigger an error?

[fatcerberus]

@dragomirtitian This is just a guess but maybe OP expects an error because 2 < 3 is always false? But then false as true isn’t an error either so…

[jko206]

I should have been more clear.

as @fatcerberus mentioned, I was expecting the above code to be an error, since the 1 < 3 is always false.

[whzx5byb]

Note that all of these are valid...

const a = false as true;
const b = 'x' as 'y';
const c = 1 as 2;

[KDwevedi]

...I was expecting the above code to be an error, since the 1 < 3 is always false.

Why is 1 < 3 false? < is just the less than comparison operator, correct?

[MartinJohns]

This is working as intended. Using a type assertion you tell the compiler "shh.. trust me, it's this type, I know what I'm doing..."

@KDwevedi They surely mean the 1 > 3 case.

[jcalz]

I'm amazed that people figured out what this issue meant. My brain was imploding trying to understand what could possibly have been the bug: "Why would the () => part matter here? Why is the desired behavior just 'an error' without mentioning, like, what kind of error? Why wouldn't you be allowed to narrow from boolean to true in a type assertion? Wait, has 3 cut in front of 1 and 2 in the number line again? Am I... am I dreaming? This is a dream, isn't it?"

[fatcerberus]

3 is always cutting in front of 1 and 2, he thinks he's so important having his visage plastered everywhere. Still better than that jerk 7. 6 still needs therapy to this day after witnessing t h e i n c i d e n t

[typescript-bot]

This issue has been marked as "Working as Intended" and has seen no recent activity. It has been automatically closed for house-keeping purposes.