cmd/go: generate silently succeeds on non-existent package

[adonovan]

I understand that go generate tries to be robust against many kinds of errors since it is often invoked on a project that won't build, but I don't think it should silently succeed when given the name of a nonexistent package:

$ go help generate
...
Generate processes packages in the order given on the command line, one at a time...
For more about specifying packages, see 'go help packages'.

$ go generate ./nonesuch; echo $?
0

[mvdan]

Sounds like a duplicate of #60079 :) At least I wasn't the only one being puzzled by this for a few minutes.