x/tools/cmd/eg: panic

[alandonovan]

% cd $GOROOT/src/cmd

% cat t.go
package template

func before() string {
        return "foo"
}
func after() string {
        return "bar"
}

% eg -t t.go cmd/internal/gc
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4c7a9d]

goroutine 1 [running]:
golang.org/x/tools/refactor/eg.(*Transformer).matchExpr(0xc20e579000, 0x7f7ce0da9b28, 0xc210222a60, 0x7f7ce0da9b28, 0x0, 0xc2080f3f30)
        /usr/local/google/home/adonovan/got3/src/golang.org/x/tools/refactor/eg/match.go:68 +0x17fd
golang.org/x/tools/refactor/eg.(*Transformer).Transform.func1(0x6a7c80, 0xc2080f3f30, 0xd6, 0x0, 0x0, 0x0)
...

[gopherbot]

CL https://golang.org/cl/34640 mentions this issue.