Feature Request: Static check involving the maps package

[zoltanhalassy]

The standard library maps package and its golang.org/x/exp/maps variant allowed newcomers to write code in a suboptimal way. Some examples found:

// exp maps, OSPACE(n) complexity
for _, k := range maps.Keys(m) { /*...*/ }
// standard library maps
for k := range maps.Keys(m) { /*...*/ }
// idiomatic
for k := range m { /*...*/ }

// exp maps, OSPACE(n) complexity
for _, v := range maps.Values(m) { /*...*/ }
// standard library maps
for v := range maps.Values(m) { /*...*/ }
// idiomatic
for _, v := range m { /*...*/ }

// exp maps, OSPACE(n) compexity, OTIME(n) complexity
if slices.Contains(maps.Keys(m), k) { /*...*/ }
// idiomatic
if _, ok := m[k]; ok { /*...*/ }

in one case, we also saw:

// standard library maps
for k, v := range maps.All(m) { /*...*/ }
// idiomatic
for k, v := range m { /*...*/ }

It would be nice to show warnings for:

• exp maps use, as the standard library has feature parity
• maps package use where it's not necessary, like directly in a range loop

[dominikh]

exp maps use, as the standard library has feature parity

We'll wait for the Go team to deprecate the package instead.

maps package use where it's not necessary, like directly in a range loop

I agree that these uses should be simplified and we can probably flag that.