cmd:compile: internal compiler error: cannot export TYPESW (130) node

[ALTree]

go version devel +e95989c1c1 Thu Mar 23 17:57:25 2017 +0000 linux/amd64

The following program:

package p

func Crash() {
	var i interface{}
	if false {
		switch i.(type) {
		}
	}
}

crashes the compiler on tip, but not in go1.8 and older.

<autogenerated>:1:0: internal compiler error: cannot export TYPESW (130) node
==> please file an issue and assign to gri@


goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/home/alberto/go/src/runtime/debug/stack.go:24 +0x79
cmd/compile/internal/gc.Fatalf(0xad7b7b, 0x47, 0xc420361540, 0x2, 0x2)
	/home/alberto/go/src/cmd/compile/internal/gc/subr.go:175 +0x230
cmd/compile/internal/gc.(*exporter).expr(0xc4203618a8, 0xc4202dfe60)
	/home/alberto/go/src/cmd/compile/internal/gc/bexport.go:1414 +0x38e
cmd/compile/internal/gc.(*exporter).exprsOrNil(0xc4203618a8, 0xc4202dfe60, 0x0)
	/home/alberto/go/src/cmd/compile/internal/gc/bexport.go:1558 +0xa2
cmd/compile/internal/gc.(*exporter).stmt(0xc4203618a8, 0xc4202dfdd0)
	/home/alberto/go/src/cmd/compile/internal/gc/bexport.go:1517 +0x787
cmd/compile/internal/gc.(*exporter).stmtList(0xc4203618a8, 0xc4202d5d00)
	/home/alberto/go/src/cmd/compile/internal/gc/bexport.go:1109 +0xf0
cmd/compile/internal/gc.(*exporter).stmt(0xc4203618a8, 0xc4202dfcb0)
	/home/alberto/go/src/cmd/compile/internal/gc/bexport.go:1496 +0x6c4
cmd/compile/internal/gc.(*exporter).stmtList(0xc4203618a8, 0xc4202d5e80)
	/home/alberto/go/src/cmd/compile/internal/gc/bexport.go:1109 +0xf0
cmd/compile/internal/gc.export(0xc4202dd800, 0x0, 0x0)
	/home/alberto/go/src/cmd/compile/internal/gc/bexport.go:388 +0x8ae
cmd/compile/internal/gc.dumpexport()
	/home/alberto/go/src/cmd/compile/internal/gc/export.go:185 +0x8a
cmd/compile/internal/gc.dumpobj1(0x7ffee3a8a1fe, 0x2f, 0x3)
	/home/alberto/go/src/cmd/compile/internal/gc/obj.go:93 +0xa5d
cmd/compile/internal/gc.dumpobj()
	/home/alberto/go/src/cmd/compile/internal/gc/obj.go:49 +0x61
cmd/compile/internal/gc.Main(0xada2d8)
	/home/alberto/go/src/cmd/compile/internal/gc/main.go:540 +0x1fee
main.main()
	/home/alberto/go/src/cmd/compile/main.go:49 +0x95

cc @griesemer

[griesemer]

I guess we are inlining more functions now than in the past.

[josharian]

Probably caused by 566e72d (CL 37499). The fix is probably to ignore such dead code when exporting.

[gopherbot]

CL https://golang.org/cl/38601 mentions this issue.