Just out of curiosity: which version of golang / go vet did you use? I do rememeber that go vet complained about these lines: https://github.com/tendermint/iavl/pull/95/files#diff-3f1ad41879763caf285707f64678af17L74

But it disappeared with upgrading golang (to 1.10.3 on darwin).

Go 1.11beta2, beta3, rc1.

go vet test modules recursively, and go test runs go vet in 1.11, so any module that explicitly or implicitly includes iavl fails in the testsuite.

Thanks!

Interestingly, only c917ed2 seems necessary to make go vet happy:

go1.11rc1 test
# github.com/tendermint/iavl
./proof_range.go:368:6: lastDepth declared but not used
vet: typecheck failures
FAIL    github.com/tendermint/iavl [build failed]

After applying c917ed2 this passes.
In any case the unreachable code doesn't make sense. If there is an overflow append will panic and the second return is still unreachable.

go test runs a subset of go vet tests. Running go vet standalone will emit the error about unreachable statement.

I also ran go1.11rc1 vet and it only complained about:

go1.11rc1 vet
# github.com/tendermint/iavl
./proof_range.go:368:6: lastDepth declared but not used
vet: typecheck failures

I was surprised about this too. I do remember vet complaining about the unreachable statement (a while ago though).

Oh, I see. go vet stops early: once you remove unused variables it starts complaining about unreachable code:

% git describe --tags
v0.9.2-1-gc917ed2
% go vet
# github.com/tendermint/iavl
./util.go:75: unreachable code