compiler: fix expanded structs in invoke calls

testdata/interface.go

@@ -13,6 +13,8 @@ func main() {
 	printItf(Number(3))
 	array := Array([4]uint32{1, 7, 11, 13})
 	printItf(array)
+	printItf(ArrayStruct{3, array})
+	printItf(SmallPair{3, 5})
 	s := Stringer(thing)
 	println("Stringer.String():", s.String())
 	var itf interface{} = s
@@ -85,3 +87,29 @@ func (a Array) Nth(n int) uint32 {
 func (a Array) Print() {
 	println("Array len:", len(a))
 }
+
+type ArrayStruct struct {
+	n int
+	a Array
+}
+
+func (a ArrayStruct) Nth(n int) uint32 {
+	return a.a[n]
+}
+
+func (a ArrayStruct) Print() {
+	println("ArrayStruct.Print:", len(a.a), a.n)
+}
+
+type SmallPair struct {
+	a byte
+	b byte
+}
+
+func (p SmallPair) Nth(n int) uint32 {
+	return uint32(int(p.a)*n + int(p.b)*n)
+}
+
+func (p SmallPair) Print() {
+	println("SmallPair.Print:", p.a, p.b)
+}

testdata/interface.txt

@@ -9,5 +9,9 @@ is *Thing: foo
 is Doubler: 6
 is Tuple: 1 7 11 13
 Array len: 4
+is Tuple: 1 7 11 13
+ArrayStruct.Print: 4 3
+is Tuple: 0 8 16 24
+SmallPair.Print: 3 5
 Stringer.String(): foo
 Stringer.(*Thing).String(): foo