cobra tests fail with "unimplemented: (reflect.Type).NumOut()"

[dkegel-fastly]

Redirecting from #2660 (comment)

Cobra's relatively popular, but doesn't seem to pass tests in tinygo 0.28.1 or 0.29.0, e.g.:

$ tinygo version
tinygo version 0.28.1 darwin/amd64 (using go version go1.20.7 and LLVM version 15.0.0)
$ git clone git@github.com:spf13/cobra.git
$ cd cobra
$ tinygo test ./...
go: downloading github.com/cpuguy83/go-md2man/v2 v2.0.2
go: downloading github.com/russross/blackfriday/v2 v2.1.0
panic: unimplemented: (reflect.Type).NumOut()
FAIL	github.com/spf13/cobra	0.330s
ok  	github.com/spf13/cobra/doc	0.304s
$ tinygo test --tags "pureno noasm appengine generic" ./...
panic: unimplemented: (reflect.Type).NumOut()

But we don't need an external package to trigger that error;
https://tinygo.org/docs/reference/lang-support/stdlib/ lists three standard library packages that fail similarly.

[dgryski]

Adding support for reflection information for functions is unlikely to appear anytime soon.