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I was actually referring to the implementation of errors.Is, which uses string comparison internally if you use the error type returned by errors.New and a type cast or switch if you use a custom type (or the cases where the stdlib defines a custom error type).


errors.Is definitely doesn't use string comparison internally:

https://cs.opensource.google/go/go/+/refs/tags/go1.24.3:src/...


Of course it does. What do you think an errors.New contains and how do you figure it compares by value when checking placeholder errors?

The answer is that errors.New just wraps the error message in an errorString struct, and the second line of `is` is a string comparison.


See for yourself: https://go.dev/play/p/Q7IPuPS5CwQ


Oh hell, I always forget equality doesn't go through pointers in go, you're right.

And as you demonstrate I could have tested it easily enough to confirm I was reading the code correctly...


My bad, I misunderstood your previous comment.




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