x/tools/gopls: modernizer max changes logic

[nemith]

Go version

go1.24.0

Output of go env in your module/workspace:

go env
AR='ar'
CC='cc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='c++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/bbennett/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/bbennett/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/ch/51hb_xjn10z7z6kvtc94dqv00000gp/T/go-build543263727=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/Users/bbennett/tmp/modernizerbugrepro/go.mod'
GOMODCACHE='/Users/bbennett/.go/pkg/mod'
GONOPROXY='<THIS IS PRIVATE!>'
GONOSUMDB='<THIS IS PRIVATE!>'
GOOS='darwin'
GOPATH='/Users/bbennett/.go'
# GOPRIVATE='<THIS IS PRIVATE!>'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/opt/homebrew/Cellar/go/1.24.0/libexec'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/bbennett/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/opt/homebrew/Cellar/go/1.24.0/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.24.0'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

Given this code:

package modernizebugrepo

import "time"

var defaultInterval = 60 * time.Second

func foo(interval time.Duration) time.Duration {
	var i time.Duration // imagine this was actually a part of an already initialized structure and isn't set to defaultInterval

	if interval <= 0 {
		i = defaultInterval
	} else {
		i = interval
	}
	return i
}

I ran go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test .

What did you see happen?

The code was "modernized" into a call to max which got rid of the defaultInterval all together.

package modernizebugrepo

import "time"

var defaultInterval = 60 * time.Second

func foo(interval time.Duration) time.Duration {
	var i time.Duration // imagine this was actually a part of an already initialized structure and isn't set to defaultInterval

	i = max(interval, 0)
	return i
}

What did you expect to see?

In this case I am guessing modernizer needs to leave the code alone. There may be some magic refactoring for this to try to use max (or min) but it really probably worth it.

[adonovan]

Fix pending in https://go.dev/cl/651375 .