proposal: cmd/gofmt: A change of spacing within for...range <int> loops

[adamroyjones]

Proposal Details

I know this is dangerously close to bike-shedding but I thought it worth the suggestion, even if it ends up being closed.

Here's a quite tortured example that's derived from something slightly less tortured.

package main

func main() {
	xs := []int{0, 1, 2}
	n := 1
	ys := make([]int, 0, len(xs)-(n-1))
	for range len(xs)-(n-1) {
		ys = append(ys, len(xs)-(n-1))
	}
}

When passed through gofmt, this becomes

package main

func main() {
	xs := []int{0, 1, 2}
	n := 1
	ys := make([]int, 0, len(xs)-(n-1))
	for range len(xs) - (n - 1) {
		ys = append(ys, len(xs)-(n-1))
	}
}

which, to my eye, seems worse. The terms after the range keyword form a tight conceptual cluster, but the text is spread.

I didn't see any discussion on #61405 about associated gofmt rules, so this may be an unintended outcome.

I propose that the spacing be as with function calls. I'm happy to have a stab at an implementation.

[seankhliao]

The formatting is consistent with when the expression is used outside of range:

_ = len(xs) - (n - 1)

[ianlancetaylor]

gofmt works without type information, so I don't know that there is any reasonable way to make this change, even if we want it.

CC @griesemer

[griesemer]

I will need to double-check but I believe this formatting solely depends on the expression and doesn't need type information. So it should be possible to do (and would be trivial to do), assuming there's agreement on it.