comparison of different types with ==, compiler says it will always evaluate to false

[lhk]

TypeScript Version: 3.8.3

Search Terms:

• comparison
• comparisons
• ==

Code

let a = "1";
let b = 1;

console.log(a == b);

Expected behavior:
Should complain about incompatible types, maybe with a warning that the == operator will lead to an implicit type conversion.

Actual behavior:
It does complain, but the error message is wrong.

error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.

This is wrong. If the code is executed, the comparison will evaluate to true.

Related Issues:
#30655. In that issue the expected behaviour was that loose comparisons of strings and numbers are considered valid. The issue was closed with a comment that an error message is intended here. I do agree with an error being the intended output. It's simply that the error message is wrong.

#29155 has exactly this problem as title but seems unrelated.

Playground Link: Provided

[WhileTrueEndWhile]

This should be correct. If you do not use any compiled code will behave right, if it compiles :-). You should not be able to compare different types. So, implicit conversions should not be valid typescript.

[lhk]

Yes, implicit conversions should not be valid typescript. I do agree.

But the error message is wrong. The condition will not always return false, just look at the playground example (where it returns true).

[nmain]

Closely related to #37251

[RyanCavanaugh]

Exact duplicate of #26592