Parse error on default constraints (...type) about cue HOT 5 CLOSED

a: {
    foo:    string  // foo is a string
    ["^i"]: int     // all other fields starting with i are integers
    ["^b"]: bool    // all other fields starting with b are booleans
    ...string       // all other fields must be a string
}

$ go get cuelang.org/go/cmd/[email protected]
go: downloading cuelang.org/go v0.4.0-beta.2
$ cue eval ./test.cue
missing ',' in struct literal:
    ./test.cue:5:8
expected '}', found 'EOF':
    ./test.cue:6:3
$ go get cuelang.org/go/cmd/[email protected]
go: downloading cuelang.org/go v0.4.0-beta.1
$ cue eval ./test.cue
a: conflicting values string and {foo:string,["^i"]:int,["^b"]:bool,...,string} (mismatched types string and struct):
    ./test.cue:1:4
    ./test.cue:5:8
$ go get cuelang.org/go/cmd/[email protected]
go: downloading cuelang.org/go v0.4.0-alpha.2
$ cue eval ./test.cue
combining bulk optional fields with other fields deprecated as of v0.2.1: try running `cue fix` using CUE v0.2.2 on the file or module to upgrade:
    ./test.cue:6:1

type: {
	field1: int
	[string]: ...string
}

$ cue version
cue version v0.4.0 linux/amd64
$ cat test.cue 
type: {
        field1: int
        [string]: ...string
}
$ cue eval test.cue 
expected operand, found '...':
    ./test.cue:3:12
expected '}', found 'EOF':
    ./test.cue:4:2