x/tools/gopls/internal/analysis/modernize: minmax generates incorrect transformation

[adonovan]

(Splitting out of #70815 (comment) on behalf of @spencerschrock.)

Currently at HEAD (44b61a1d174cc06329b20f5de60c2b0c800741a4):

main.go:7:5: if/else statement can be modernized using max

package main

import "fmt"

func main() {
	var x, y int
	if x <= 0 { // a value of -1 or 0 will use a default value (30)
		y = 30
	} else {
		y = x
	}
	fmt.Print(y)
}

Applying the suggested fix doesn't yield an equivalent result:

package main

import "fmt"

func main() {
	var x, y int
	y = max(x, 0)
	fmt.Print(y)
}

[gopherbot]

Change https://go.dev/cl/649357 mentions this issue: gopls/internal/analysis/modernize: fix bug in minmax

[findleyr]

This did not make it into v0.18.0, as it was not cherry-picked.

Moving to v0.18.1, and reopening to track the cherry-pick.

[gopherbot]

Change https://go.dev/cl/651236 mentions this issue: [gopls-release-branch.0.18] gopls/internal/analysis/modernize: fix bug in minmax

[findleyr]

Closing as the cherry pick has occurred.