cmd/go: go get panics when import path contains "cmd/something"

[gopherbot]

by toffaletti:

What does 'go version' print?

go version go1.2.1 darwin/amd64

What steps reproduce the problem?
If possible, include a link to a program on play.golang.org.

I have a git repo https://github.com/toffaletti/gogetpanic that reproduces the problem.
Check out the repo and run make, which is just running go get -d -t ./... after setting
GOPATH.

What happened?

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x58 pc=0x25b83]

goroutine 1 [running]:
runtime.panic(0x35c9e0, 0x77ff99)
    /usr/local/go/src/pkg/runtime/panic.c:266 +0xb6
main.downloadPackage(0xc210151c00, 0xc210085600, 0xc2100b9c01)
    /usr/local/go/src/cmd/go/get.go:259 +0x33
main.download(0xc2100b9c01, 0x15, 0xc210095600, 0x0)
    /usr/local/go/src/cmd/go/get.go:166 +0x9ea
main.download(0xc2100aa320, 0x14, 0xc210095600, 0xc2100b9301)
    /usr/local/go/src/cmd/go/get.go:232 +0x70a
main.runGet(0x77d100, 0xc21000a050, 0x1, 0x1)
    /usr/local/go/src/cmd/go/get.go:72 +0xc8
main.main()
    /usr/local/go/src/cmd/go/main.go:161 +0x4f1

goroutine 3 [syscall]:
os/signal.loop()
    /usr/local/go/src/pkg/os/signal/signal_unix.go:21 +0x1e
created by os/signal.init·1
    /usr/local/go/src/pkg/os/signal/signal_unix.go:27 +0x31
make: *** [default] Error 2

What should have happened instead?

go get should find the "cmd/everything/widget" import path in GOPATH or at
least tell me not to have this kind of ridiculous import path instead of just panic.

[ianlancetaylor]

Comment 1:

Labels changed: added repo-main, release-go1.3.

[minux]

Comment 2:

Status changed to Accepted.

[gopherbot]

Comment 3:

CL https://golang.org/cl/87300043 mentions this issue.

[gopherbot]

Comment 4:

This issue was closed by revision 3f529f8.

Status changed to Fixed.

[gopherbot]

Comment 5:

CL https://golang.org/cl/87890043 mentions this issue.

[adg]

Comment 6:

This issue was closed by revision 85ddc68.

[adg]

Comment 7:

I just rolled back 87300043 because it broke the build. Re-opening this issue.

Status changed to Accepted.

[gopherbot]

Comment 8:

CL https://golang.org/cl/89280043 mentions this issue.

[gopherbot]

Comment 9:

This issue was closed by revision eeb87c3.

Status changed to Fixed.