Hacker News Reader

it wasn't accidental -- it was written on purpose by a programmer (a conversion from Writer to WriteCloser). it was immediately acknowledged as an error and eventually may be caught by the standard code examining tool "vet".

View on HN

What would the static analysis that "vet" is performing enforce to stop this? No interface-to-interface downcasts?

eventually, within the context of the `go vet` tool, the http://godoc.org/code.google.com/p/go.tools/go/types package may be used to analyze interface conversions ("I said I expected interface type A, but I'm using it as interface type B", which is unusual for go programs). i think that answers "yes" to your second question, but I'm not on the go team, so take my opinion with a grain of salt.

short of disallowing interface-to-interface casts, it is indicative of an error and should be vetted as such. the particular case I described earlier was covered by the Go 1.0 guarantee, so it had to be documented rather than fixed.

Hmm. Seems hard to do soundly in the presence of higher order control flow (e.g. pass the interface to a closure in a global variable—will the closure downcast it to another interface you didn't expect?)

Reply on news.ycombinator.com