elvish crash when pressing tab after the equals sign in an assignment

-

[~]─> a = <tab>

runtime error: invalid memory address or nil pointer dereference
goroutine 1 [running]:
github.com/elves/elvish/sys.DumpStack(0xc42045f018, 0x1)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/sys/dumpstack.go:7 +0x79
github.com/elves/elvish/shell.rescue()
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/shell/shell.go:68 +0xd2
panic(0x45a41a0, 0x4892680)
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/panic.go:489 +0x2cf
github.com/elves/elvish/edit/nodeutil.SimpleCompound(0x0, 0x0, 0xc420239280, 0x4014607, 0x4, 0x0, 0xc420147520)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/edit/nodeutil/nodeutil.go:14 +0x2c
github.com/elves/elvish/edit.simpleCompound(0x0, 0x0, 0x4, 0x4, 0x0, 0x0, 0x1)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/edit/nodeutil.go:30 +0x35
github.com/elves/elvish/edit.complArg(0x486f980, 0xc4201cd040, 0xc420128690, 0xc42012c9a0, 0x4866501, 0xc42012c9a0)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/edit/completers.go:394 +0xbe
github.com/elves/elvish/edit.complete(0x486f980, 0xc4201cd040, 0xc420128690, 0x486f980, 0xc4201cd040, 0x4, 0x100000001, 0x0)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/edit/completers.go:86 +0x8a
github.com/elves/elvish/edit.startCompletionInner(0xc4201a8000, 0xc420239601)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/edit/completion.go:192 +0xa1
github.com/elves/elvish/edit.complSmartStart(0xc4201a8000)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/edit/completion.go:85 +0x30
github.com/elves/elvish/edit.(*Editor).CallFn(0xc4201a8000, 0x486d440, 0xc420130dc0, 0x0, 0x0, 0x0)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/edit/api.go:151 +0x5f8
github.com/elves/elvish/edit.(*Editor).ReadLine(0xc4201a8000, 0x0, 0x0, 0x0, 0x0)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/edit/editor.go:448 +0x9c1
github.com/elves/elvish/shell.interact.func1(0x45badc0, 0xc42013a930, 0x1e, 0x462e201)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/shell/shell.go:128 +0x2a
github.com/elves/elvish/shell.interact(0xc420128690, 0xc42012b260)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/shell/shell.go:139 +0x145
github.com/elves/elvish/shell.(*Shell).Run(0xc420125f18, 0xc420010210, 0x0, 0x0, 0x0)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/shell/shell.go:57 +0x1bf
main.main()
	/private/tmp/elvish-20170715-9639-kxuaux/main.go:143 +0x4b7

goroutine 17 [syscall, 4 minutes, locked to thread]:
runtime.goexit()
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/asm_amd64.s:2197 +0x1

goroutine 6 [chan receive]:
github.com/elves/elvish/shell.logSignals.func1(0xc4201a4000)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/shell/shell.go:176 +0x5a
created by github.com/elves/elvish/shell.logSignals
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/shell/shell.go:179 +0x8a

goroutine 18 [syscall]:
os/signal.signal_recv(0x486b740)
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/sigqueue.go:116 +0xff
os/signal.loop()
	/usr/local/Cellar/go/1.8.3/libexec/src/os/signal/signal_unix.go:22 +0x22
created by os/signal.init.1
	/usr/local/Cellar/go/1.8.3/libexec/src/os/signal/signal_unix.go:28 +0x41

goroutine 19 [chan receive, 4 minutes]:
github.com/elves/elvish/eval.init.3.func1()
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/eval/port.go:56 +0x5a
created by github.com/elves/elvish/eval.init.3
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/eval/port.go:58 +0x49

goroutine 20 [IO wait, 4 minutes]:
net.runtime_pollWait(0x4d44f00, 0x72, 0x4)
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/netpoll.go:164 +0x59
net.(*pollDesc).wait(0xc42014adf8, 0x72, 0x4868e00, 0x48648d8)
	/usr/local/Cellar/go/1.8.3/libexec/src/net/fd_poll_runtime.go:75 +0x38
net.(*pollDesc).waitRead(0xc42014adf8, 0xc420187000, 0x1000)
	/usr/local/Cellar/go/1.8.3/libexec/src/net/fd_poll_runtime.go:80 +0x34
net.(*netFD).Read(0xc42014ad90, 0xc420187000, 0x1000, 0x1000, 0x0, 0x4868e00, 0x48648d8)
	/usr/local/Cellar/go/1.8.3/libexec/src/net/fd_unix.go:250 +0x1b7
net.(*conn).Read(0xc420132040, 0xc420187000, 0x1000, 0x1000, 0x0, 0x0, 0x0)
	/usr/local/Cellar/go/1.8.3/libexec/src/net/net.go:181 +0x70
bufio.(*Reader).Read(0xc420150180, 0xc42012d740, 0x1, 0x9, 0x0, 0xc420049c28, 0x402b2df)
	/usr/local/Cellar/go/1.8.3/libexec/src/bufio/bufio.go:213 +0x312
io.ReadAtLeast(0x4866000, 0xc420150180, 0xc42012d740, 0x1, 0x9, 0x1, 0xc420049d00, 0x402b006, 0x0)
	/usr/local/Cellar/go/1.8.3/libexec/src/io/io.go:307 +0xa9
io.ReadFull(0x4866000, 0xc420150180, 0xc42012d740, 0x1, 0x9, 0xc420000340, 0x4, 0x8)
	/usr/local/Cellar/go/1.8.3/libexec/src/io/io.go:325 +0x58
encoding/gob.decodeUintReader(0x4866000, 0xc420150180, 0xc42012d740, 0x9, 0x9, 0xc420049d48, 0x402a93e, 0xc400000008, 0xc42011c080)
	/usr/local/Cellar/go/1.8.3/libexec/src/encoding/gob/decode.go:119 +0x63
encoding/gob.(*Decoder).recvMessage(0xc420134280, 0xc420049d58)
	/usr/local/Cellar/go/1.8.3/libexec/src/encoding/gob/decoder.go:76 +0x57
encoding/gob.(*Decoder).decodeTypeSequence(0xc420134280, 0x464d700, 0xc420134280)
	/usr/local/Cellar/go/1.8.3/libexec/src/encoding/gob/decoder.go:140 +0x167
encoding/gob.(*Decoder).DecodeValue(0xc420134280, 0x4567400, 0xc420138240, 0x16, 0x0, 0x0)
	/usr/local/Cellar/go/1.8.3/libexec/src/encoding/gob/decoder.go:208 +0xe8
encoding/gob.(*Decoder).Decode(0xc420134280, 0x4567400, 0xc420138240, 0x0, 0x0)
	/usr/local/Cellar/go/1.8.3/libexec/src/encoding/gob/decoder.go:185 +0x16d
net/rpc.(*gobClientCodec).ReadResponseHeader(0xc42012b350, 0xc420138240, 0xc4201a6150, 0x0)
	/usr/local/Cellar/go/1.8.3/libexec/src/net/rpc/client.go:223 +0x45
net/rpc.(*Client).input(0xc420150240)
	/usr/local/Cellar/go/1.8.3/libexec/src/net/rpc/client.go:109 +0xc9
created by net/rpc.NewClientWithCodec
	/usr/local/Cellar/go/1.8.3/libexec/src/net/rpc/client.go:201 +0xc5

goroutine 21 [select, locked to thread]:
runtime.gopark(0x464d718, 0x0, 0x462df73, 0x6, 0x18, 0x2)
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/proc.go:271 +0x13a
runtime.selectgoImpl(0xc420039f50, 0x0, 0x18)
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/select.go:423 +0x1364
runtime.selectgo(0xc420039f50)
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/select.go:238 +0x1c
runtime.ensureSigM.func1()
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/signal_unix.go:434 +0x265
runtime.goexit()
	/usr/local/Cellar/go/1.8.3/libexec/src/runtime/asm_amd64.s:2197 +0x1

goroutine 34 [chan receive, 4 minutes]:
github.com/elves/elvish/shell.handleUsr1AndQuit.func1(0xc4201508a0)
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/shell/shell.go:186 +0x57
created by github.com/elves/elvish/shell.handleUsr1AndQuit
	/private/tmp/elvish-20170715-9639-kxuaux/src/github.com/elves/elvish/shell/shell.go:189 +0xe6

execing recovery shell /bin/sh
sh-3.2$