Fix type propagation in calls returning multiple values

_test/ret2.go

@@ -1,11 +1,11 @@
 package main
 
+func r2() (int, int) { return 1, 2 }
+
 func main() {
 	a, b := r2()
 	println(a, b)
 }
 
-func r2() (int, int) { return 1, 2 }
-
 // Output:
 // 1 2