cmd/gofmt: align struct tag of embedded type with surrounding fields

[dolmen]

Struct tag of embedded types is not aligned with tags of surrounding struct fields.

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

$ go version
go version go1.17.8 darwin/amd64

Does this issue reproduce with the latest release?

Yes (1.17.8).

Also gotip on the Go Playground.

What did you do?

Apply gofmt to the following code.

type B string

type _ struct {
	A string `json:"a"`
	B `json:"b"`
	C int     `json:"c"`
	D float32 `json:"d"`
}

Use the 'Format' button on the Go Playground.

What did you expect to see?

type _ struct {
	A string  `json:"a"`
	B         `json:"b"`
	C int     `json:"c"`
	D float32 `json:"d"`
}

What did you see instead?

No change in formatting.

type _ struct {
	A string `json:"a"`
	B `json:"b"`
	C int     `json:"c"`
	D float32 `json:"d"`
}

[mengzhuo]

CC @griesemer @mvdan per owner

[mvdan]

I think this makes sense. One could think that breaking the alignment draws attention to the embedded field, making it stand out more, but I don't imagine that was intentional.

Beware that the vertical alignment, such as with inline comments, is based on a heuristic and may be broken if there's a sudden change in the amount of needed whitespace. I don't think that's happening here, but still worth keeping in mind.