reflect: StructOf allows creation of structs with invalid field names

[dsnet]

Using Go1.8.3

t := reflect.StructOf([]reflect.StructField{
	reflect.StructField{Name: "", Type: reflect.TypeOf(0)},
	reflect.StructField{Name: "+", Type: reflect.TypeOf(0)},
})
fmt.Printf("%#v\n", reflect.New(t).Elem())

What did I see:
The creation of a struct with ridiculous field names.

struct { int; + int }{int:0, +:0}

What did I expect:
A panic of some sort.

[bradfitz]

/cc @crawshaw @ianlancetaylor

[pravj]

If I'm allowed, I would like to work on it.

Right now, it's only checking for an empty field name.

...
if field.Name == "" {
        panic("reflect.StructOf: field " + strconv.Itoa(i) + " has no name")
}
...

According to the language spec, a field name should be an identifier.

identifier = letter { letter | unicode_digit } .

letter = unicode_letter | "_" .

An extra check can be applied to make sure the field name matches the correct form.

[ianlancetaylor]

@pravj Please go ahead. Thanks.

[pravj]

@ianlancetaylor,

I've implemented a function to verify the field name and tested it, but I'm facing an issue following the contribution guideline.

The git change command is reporting error because of a previous change by @rsc.

git-codereview: gofmt reported errors:
	reflect/all_test.go:5991:12: expected type, found '='

Sorry for starting the conversation here, as I wasn't able to make a change list because of this error.

[pravj]

Just to be clear, this file all_test.go is in my staged changes because I've written corresponding test for the field-name-verification in it.

[odeke-em]

@pravj if you can go into your $GOPATH/bin and remove gofmt then try again I think it should work.
Seems like your gofmt in the bin directory is stale and needs to be rebuilt.

You can always rebuild with ./make.bash although that for some reason(but I was able to run it even before the rebuild), it didn't rebuild my gofmt so I built it like this:

$ cd $GOPATH/src/go.googlesource.com/go/src/cmd/gofmt && go build -o $GOPATH/bin/gofmt

and when ready run gofmt on your test, commit then you should be gucci to go!

[pravj]

@odeke-em, I'm still getting the same error as I enter the git change command. I have tried building gofmt again and again.

Also, the cloned source (that I'm working with) shouldn't be in the $GOPATH as suggested in the contribution guide.

You should checkout the Go source repo anywhere you want as long as it's outside of your $GOPATH

So I'm unable to digest the directory change you did to the source repo but inside $GOPATH.

Didn't expect this while doing my first contribution, getting nervous.

[ianlancetaylor]

@pravj You need to build gofmt using the tip version of Go, not Go 1.8. The problem is that the future Go 1.9 adds a new language change: type aliases. You need to build a version of gofmt that uses the go/parse package from the future Go 1.9.

[gopherbot]

CL https://golang.org/cl/45590 mentions this issue.