add auto fix

[batazor]

auto fix from for i := 0; i < 100; i++ to for i := range 100

[cespare]

I made a (very quick and dirty and still buggy) tool for myself which changes for statements to use range-over-int if possible. In case it's useful, here's the bit that does the editing: https://github.com/cespare/misc/blob/188b9f2b335bef60681a649d5a0e344d0f7446fe/useintrange/useintrange.go#L258-L297

[ckaznocha]

Thanks @cespare, for clarity, the delay in adding autofixes is more about compatibility with golangci-lint.

They were not added initially because golangci-lint had a minimum go version of 1.21 as ranging over integers was introduced in go 1.22 it would have been awkward to change working code to unsupported code. golangci-lint has since added version detection so that is no longer a concern.

In #28 I added an autofix to simplify some ranges using analysis.SuggestedFix however golangci-lint doesn't support analysis.SuggestedFix. See golangci/golangci-lint#1779.

I plan on adding more autofixes when golangci-lint can support analysis.SuggestedFix but I'm not sure in the meantime I'd try to use their bespoke autofix system. I would be happy to review a PR if anyone wanted to contribute a golangci-lint compatible autofix.

[ckaznocha]

Implement suggested fixes for:

• 3 statement loops where the key is not used in the body (Suggested fixes for ranges that do not need the key #39)
• 3 statement loops where the key is used in the body (Add analysis.SuggestedFix for range over int #34, Update range autofix #35)
• range loops with redundant len where the key is not used in the body (Warn about loops using range len(b) with arrays/slices #28)
• range loops with redundant len where the key is used in the body (Warn about loops using range len(b) with arrays/slices #28)

No suggested fixes for:

• 3 statement loops where the key belongs to a different scope (Add note about scopes on assignment #37) ref: Disable the linter if loop variable is used after the loop #33 (comment)