cmd/compile: internal compiler error, evconst changed Type

[bradfitz]

This works on Go 1.8, but fails in Go 1.9 and Go tip (~Go 1.10beta2):

package main

func main() {
        type T struct{}
        var s = struct {
                t1 T
                _  int
                t2 T
        }{}
        print(len(map[*T]int{&s.t1: 0, &s.t2: 0}))
}

bradfitz@gdev:~$ go run x.go
# command-line-arguments
<autogenerated>:1:0: internal compiler error: evconst changed Type: true && true had type bool, now untyped bool

goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
        /home/bradfitz/go/src/runtime/debug/stack.go:24 +0xa7
cmd/compile/internal/gc.Fatalf(0xc26e98, 0x2c, 0xc4204bcc80, 0x3, 0x3)
        /home/bradfitz/go/src/cmd/compile/internal/gc/subr.go:182 +0x1f2
cmd/compile/internal/gc.walkexpr(0xc420312000, 0xc420312090, 0xc4204f4ed0)
        /home/bradfitz/go/src/cmd/compile/internal/gc/walk.go:1745 +0xae0
cmd/compile/internal/gc.walkexprlist(0xc4204cc380, 0x1, 0x1, 0xc420312090)
        /home/bradfitz/go/src/cmd/compile/internal/gc/walk.go:378 +0x50
cmd/compile/internal/gc.walkstmt(0xc420312080, 0xc4204bcf01)
        /home/bradfitz/go/src/cmd/compile/internal/gc/walk.go:292 +0x11f
cmd/compile/internal/gc.walkstmtlist(0xc4204cc390, 0x1, 0x1)
        /home/bradfitz/go/src/cmd/compile/internal/gc/walk.go:78 +0x46
cmd/compile/internal/gc.walk(0xc420001980)
        /home/bradfitz/go/src/cmd/compile/internal/gc/walk.go:62 +0x3a1
cmd/compile/internal/gc.compile(0xc420001980)
        /home/bradfitz/go/src/cmd/compile/internal/gc/pgen.go:203 +0xae
cmd/compile/internal/gc.funccompile(0xc420001980)
        /home/bradfitz/go/src/cmd/compile/internal/gc/dcl.go:1040 +0xad
cmd/compile/internal/gc.geneq(0xc42050faa0, 0xc420341140)
        /home/bradfitz/go/src/cmd/compile/internal/gc/alg.go:503 +0x790
cmd/compile/internal/gc.dalgsym(0xc420341140, 0xffffffffffffffff)
        /home/bradfitz/go/src/cmd/compile/internal/gc/reflect.go:1685 +0x5c4
cmd/compile/internal/gc.dcommontype(0xc42050a000, 0x0, 0xc420341140, 0x58)
        /home/bradfitz/go/src/cmd/compile/internal/gc/reflect.go:856 +0xa3
cmd/compile/internal/gc.dtypesym(0xc420341140, 0xc42050a150)
        /home/bradfitz/go/src/cmd/compile/internal/gc/reflect.go:1360 +0xd19
cmd/compile/internal/gc.dumpsignats()
        /home/bradfitz/go/src/cmd/compile/internal/gc/reflect.go:1511 +0x341
cmd/compile/internal/gc.dumpobj1(0x7ffc8fb3010c, 0x23, 0x3)
        /home/bradfitz/go/src/cmd/compile/internal/gc/obj.go:139 +0x2a1
cmd/compile/internal/gc.dumpobj()
        /home/bradfitz/go/src/cmd/compile/internal/gc/obj.go:50 +0x51
cmd/compile/internal/gc.Main(0xc2e5f8)
        /home/bradfitz/go/src/cmd/compile/internal/gc/main.go:683 +0x2b0e
main.main()
        /home/bradfitz/go/src/cmd/compile/main.go:49 +0x89

/cc @dsnet @mdempsky @griesemer

[bradfitz]

Oh, dup of #23414.