cmd/compile: ugly error message for weird invalid program

[josharian]

package p

var r = newReader()

func newReader() r

$ go tool compile x.go 
x.go:3:9: typechecking loop involving newReader
	x.go:3:18 newReader()
	x.go:3:5 r = newReader()
	x.go:3:5 r
	x.go:5:15 <T>
	x.go:5:18 newReader
	x.go:5:6 <node DCLFUNC>
x.go:5:18: r is not a type

This error message is ugly and inscrutable.

The same program features in #20770.

Marking as unplanned, because of the oddity and unlikeliness of the program.

Found with go-fuzz.

[ALTree]

This looks fixed. In 1.10 and 1.11 the error message is:

# command-line-arguments
./test.go:5:6: missing function body
./test.go:5:18: r is not a type

Closing here.