proposal: cmd/vet: warn when zero values make explicit initialisation unnecessary

[jokeyrhyme]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.8.3 darwin/amd64

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"

What did you do?

import (
  "sync"
  "time"
)

type Thing struct {
  mutex sync.RWMutex
  time time.Time
}

func NewThing() *Thing {
  return &Thing{
    mutex: sync.RWMutex{},
    time: time.Unix(0, 0),
  }
}

What did you expect to see?

Proposal: go vet should warn when initialising a value is unnecessary, i.e. when the zero value for the type is effectively equal to the explicitly initialised value

As someone new to the language, I have not memorised which types have a zero value and what those zero values are

I will look these up now that I know about them, but go vet could help me and others in this case

What did you see instead?

go vet does not indicate any issues about unnecessary initialisation

[ianlancetaylor]

See cmd/vet/README for guidelines for vet checks. I think this one fails the "correctness" criterion: unnecessary initialization is not a bug.

[jokeyrhyme]

@ianlancetaylor
yep, found it: https://github.com/golang/go/blob/master/src/cmd/vet/README

Correctness:

Vet's tools are about correctness, not style. A vet check must identify real or
potential bugs that could cause incorrect compilation or execution. A check that
only identifies stylistic points or alternative correct approaches to a situation
is not acceptable.

I agree that unnecessary initialisation is not a bug

I've filed this as a suggestion for golint instead: golang/lint#317