cmd/vet: crashes on "C.f(*p(**q))"

[mwhudson]

I presume this is from https://go-review.googlesource.com/#/c/17041/ ? (@ianlancetaylor?)

mwhudson@aeglos:go-test-cases$ go build vet.go
# command-line-arguments
./vet.go:3: undefined: C in C.f
./vet.go:3: undefined: p
mwhudson@aeglos:go-test-cases$ cat vet.go 
package p

var _ = C.f(*p(**p))

mwhudson@aeglos:go-test-cases$ go vet vet.go
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x28 pc=0x40b5a3]

goroutine 1 [running]:
main.cgoBaseType(0xc8200ba000, 0x7f4a7608ec58, 0xc8200b2640, 0x0, 0x0)
    /opt/opensource/go/src/cmd/vet/cgo.go:75 +0x2d3
main.checkCgoCall(0xc8200ba000, 0x7f4a7608e930, 0xc8200134c0)
    /opt/opensource/go/src/cmd/vet/cgo.go:42 +0x1ad
main.(*File).Visit(0xc8200ba000, 0x7f4a7608e930, 0xc8200134c0, 0x0, 0x0)
    /opt/opensource/go/src/cmd/vet/main.go:485 +0x1ba
go/ast.Walk(0x7f4a7608efd0, 0xc8200ba000, 0x7f4a7608e930, 0xc8200134c0)
    /opt/opensource/go/src/go/ast/walk.go:52 +0x56
go/ast.walkExprList(0x7f4a7608efd0, 0xc8200ba000, 0xc8200b42e0, 0x1, 0x1)
    /opt/opensource/go/src/go/ast/walk.go:26 +0xd5
go/ast.Walk(0x7f4a7608efd0, 0xc8200ba000, 0x7f4a7608f028, 0xc8200b1bd0)
    /opt/opensource/go/src/go/ast/walk.go:308 +0xf63
go/ast.Walk(0x7f4a7608efd0, 0xc8200ba000, 0x7f4a7608ea50, 0xc820013500)
    /opt/opensource/go/src/go/ast/walk.go:331 +0x1f7d
go/ast.walkDeclList(0x7f4a7608efd0, 0xc8200ba000, 0xc8200b4310, 0x1, 0x1)
    /opt/opensource/go/src/go/ast/walk.go:38 +0xd5
go/ast.Walk(0x7f4a7608efd0, 0xc8200ba000, 0x7f4a7608ed70, 0xc82008e600)
    /opt/opensource/go/src/go/ast/walk.go:353 +0x29b9
main.(*File).walkFile(0xc8200ba000, 0x7ffd3bd0fdef, 0x6, 0xc82008e600)
    /opt/opensource/go/src/cmd/vet/main.go:454 +0x1f5
main.doPackage(0x7a0398, 0x1, 0xc82000a650, 0x1, 0x1, 0x0)
    /opt/opensource/go/src/cmd/vet/main.go:353 +0xd97
main.main()
    /opt/opensource/go/src/cmd/vet/main.go:243 +0x420
exit status 2

[gopherbot]

CL https://golang.org/cl/19174 mentions this issue.