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• I have searched for related issues and found none that match my proposal.
• I have searched the current rule list and found no rules that match my proposal.
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Link to the rule's documentation

https://typescript-eslint.io/rules/no-unnecessary-condition/

Description

I've thought more about the error message change in #9643 / #10194, and I'm not happy with the current error message (changed in #10194).

'Unnecessary conditional, comparison is always {{trueOrFalse}}. Both sides of the comparison always have a literal type.' is more helpful than the prior message was, yes, but it doesn't fully explain what we're flagging to the user.

I propose we change it to 'Unnecessary conditional, comparison is always {{trueOrFalse}}, since {{left}} {{operator}} {{right}} is {{trueOrFalse}}.', so that something like if (expressionResultingInMinus55 < expressionResultingIn23) {} will report an error as 'Unnecessary conditional, comparison is always true, since -55 < 23 is true.'.

This would IMO make it clearer what types we're seeing and why that indicates the expression has a constant value, helping the user assess whether the types are correct before resolving the complaint.

I have successfully implemented this in #10454 and I find the reports to be a big improvement when experimenting with it in the playground.

Fail

// unnecessary condition; 1 === 2 is false
if (1 === 2) {}


declare const expressionResultingIn23: 23;
declare const expressionResultingInMinus55: -55;

// unnecessary condition; -55 < 23 is true.
if (expressionResultingInMinus55 < expressionResultingIn23) {}

Pass

n/a

Additional Info

cc @StyleShit