I think what is going on here is that it is wrong to say that `(*observer)` creates a copy:
https://golang.org/ref/spec#Address_operators > For an operand x of pointer type *T, the pointer indirection *x denotes > the variable of type T pointed to by x. That variable is addressable and contains a `sync.RWMutex`. It's method set contains `Lock`, as methods on a pointer receiver are promoted to value receivers <https://golang.org/ref/spec#Method_sets>. And "If x is addressable and &x's method set contains m, x.m() is shorthand for (&x).m()" <https://golang.org/ref/spec#Calls>. Thus, `(*observer).Lock()` is a shorthand for `(&(*observer)).Lock()` which is the same as `observer.Lock()`. If, OTOH, you do lock := (*observer) lock.Lock() you *would* create a copy - you'd create a new variable and assign to it the value in the variable pointed at by observer. Either way, I think that code should be changed. It's pretty messy and obviously not clear, even if it's correct. On Thu, Apr 22, 2021 at 1:49 PM Jan Mercl <0xj...@gmail.com> wrote: > On Thu, Apr 22, 2021 at 1:39 PM Mikhail Mazurskiy > <mikhail.mazur...@gmail.com> wrote: > > > Thanks for the response, I didn't see this section. However, I'm still > confused as it says the exception in 3. only applies to fields, not to > methods. RLock() is obviously a method, not a field. > > You're right. And because the playground link seems to work for > methods as well, I'm now pretty confused if there's a compiler bug or > specs bug or I don't understand what's going on at all. > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/CAA40n-WdkuXq2u1NYfPWL2pJYq6m1pBrhEOA-qsToNUeVkFz2Q%40mail.gmail.com > . > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAEkBMfEm6%3DuyPhYf%3DZnRpQXYVm2wpTDsSZnmY2_KGM0OKWgW2g%40mail.gmail.com.
