This might be because, until recently, vet did not always have type information. Should be fairly easy to make the check precise.

As far as I understand, check for print functions will be executed by default before tests in go 1.10. Check results will be treated as errors. Can this be a reason to fix this before 1.10 or, at least, disable the check for this particular case?

That's a good point. Not a regression in vet, but could qualify as a regression in test. /cc @rsc

Actually, I'm not 100% sure if fmt is right here. I know that the program does run, but I don't follow the logic as to why it doesn't crash with an infinite recursion. /cc @robpike

@mvdan the address is taken twice (once implicitly then once explicitly) so it's a **X which has no method set

Vet should not complain here. The code is legal and should (and does) print the address of x, of type **X. The argument to Sprint has no method set.

Thank you both. I do understand the double pointer - what still confuses me at times is what rules apply when a method of *T can be called on T (and vice versa). Thanks for confirming that the code is right before I looked into a fix.

Indeed - the problem is that vet tracked only the types that had a String() string method declared on them, but it did not track whether the receiver in the method had a pointer type. With that extra information, we can now fix this false positive.

Change https://golang.org/cl/90417 mentions this issue: cmd/vet: **T is not Stringer if *T has a String method