go version devel +4a839bf01b58 Tue May 20 15:52:08 2014 +1000 + linux/amd64

The program is:

package b
var B = []*[2][1]float64{}

package a
import "b"
var X = b.B
func a() {
    _ = [3][1]float64{}
}

$ go build a
a.go:1: constant -1000000000 overflows uintptr

The error is triggered when generating hash function for [2][1]float64 in package a:
# a
before type..hash.[2][1]float64
[SKIP]
.   .   CALLFUNC l(1) tc(1)
.   .   .   NAME-type..hash.[1]float64 u(1) a(1) l(1) x(0+0) class(PFUNC) tc(1) used(1)
FUNC-funcSTRUCT-(FIELD-PTR64-*uintptr, FIELD-uintptr, FIELD-PTR64-*ARRAY-[1]float64)
.   .   CALLFUNC-list
.   .   .   NAME-a.h u(1) a(1) g(1) l(1) x(0+0) class(PPARAM) f(1) tc(1) used(1)
PTR64-*uintptr

.   .   .   LITERAL--1000000000 u(1) a(1) l(1) tc(1) uintptr

.   .   .   ADDR l(1) tc(1) PTR64-*ARRAY-[1]float64
.   .   .   .   INDEX l(1) tc(1) ARRAY-[1]float64
.   .   .   .   .   IND l(1) tc(1) implicit(1) ARRAY-[2]ARRAY-[1]float64
.   .   .   .   .   .   NAME-a.p u(1) a(1) g(3) l(1) x(16+0) class(PPARAM) f(1) tc(1)
used(1) PTR64-*ARRAY-[2]ARRAY-[1]float64
.   .   .   .   .   NAME-a.i u(1) a(1) g(4) l(1) x(0+0) class(PAUTO) f(1) tc(1) used(1)
int


-1000000000 seems to be BADWIDTH.