ir: do not throw an error on unknown conversions

testdata/init.go

@@ -6,4 +6,26 @@ func init() {
 
 func main() {
 	println("main")
+	println("v1:", v1)
+	println("v2:", v2.x, v2.y)
+	println("v3:", len(v3), cap(v3), v3[0], v3[3])
+	println("v4:", len(v4), v4 == nil)
+	println("v5:", len(v5), v5 == nil)
+	println("v6:", v6)
 }
+
+type (
+	t2 struct {
+		x int
+		y int
+	}
+)
+
+var (
+	v1 = 3
+	v2 = t2{2, 5}
+	v3 = []int{2, 3, 5, 7}
+	v4 map[string]int
+	v5 = map[string]int{}
+	v6 = float64(v1) < 2.6
+)

testdata/init.txt

@@ -1,2 +1,8 @@
 init
 main
+v1: 3
+v2: 2 5
+v3: 4 4 2 7
+v4: 0 true
+v5: 0 false
+v6: false