cmd/vet: detect stupid conditions

[rsc]

It would be nice if vet detected a few obviously stupid boolean conditions. This can
probably be done purely at a syntactic level, without recourse to any type checking.

x == y || x == y
is a redundant test, assuming neither x nor y contains function calls or channel
operations.

x != y || x != z
is not guaranteed to be wrong but almost always is. If y and z are the same then it's
redundant; if y and z are different then it's always true.

[josharian]

Comment 1:

Not sure whether this belongs in vet (vs golint), but on the topic of stupid boolean
conditions, x == false should be !x.

[josharian]

Comment 2:

Owner changed to @josharian.

Status changed to Started.

[josharian]

Comment 3:

I've come to the conclusion that flagging cases like x == false is a better fit for go
lint, and filed golang/lint#45 accordingly. CL for rsc's
original check coming soon.

[gopherbot]

Comment 4:

CL https://golang.org/cl/98120043 mentions this issue.

[josharian]

Comment 5:

This issue was closed by revision golang/tools@7da5f19.

Status changed to Fixed.