x/tools/cmd/vet: complain about incomplete switch statements

[robpike]

From the mailing list:

A year ago, around Google I/O, we were talking about Go
wishlist items and it came up that some people miss having
a compiler that checks switch case coverage (like some C
compilers do with enums). As I recall, Rob said it doesn't
belong in the compiler (naturally) but would be a good
addition to go vet.

Not sure about the details, but I think the general idea would
be to have go vet report a problem when some but not all
values from a const block are used as cases in a switch.

[rsc]

Comment 1:

I hope this never happens, at least not by default. I hate when C and C++ compilers
whine about me using a switch statement to look for just a few values.

[robpike]

Comment 2:

This is a feature request for vet, not the compilers.  Maybe that mitigates enough to be
worthwhile, although I too dislike the C++ warnings (along with many others).

[rsc]

Comment 3:

I know, but things that vet complains about have a way of becoming verboten. I am sure
that if it ends up in vet someone will start sending me CLs "fixing" my code.

[robpike]

Comment 4:

Then just say no.
I'm not arguing for this feature, but if vet becomes law I'd rather delete it than fight
the users.

[rsc]

Comment 5:

Okay. If it happens I will send a link to the previous comment. :-)

[rsc]

Comment 6:

Labels changed: added go1.3maybe.

[rsc]

Comment 7:

Labels changed: removed feature.

[rsc]

Comment 8:

Labels changed: added release-none, removed go1.3maybe.

[rsc]

Comment 9:

Labels changed: added repo-tools.

[robpike]

Decided not to do this.