diff --git a/README.md b/README.md
index fed235f6..5762e3dd 100644
--- a/README.md
+++ b/README.md
@@ -291,6 +291,10 @@ Here are the Go packages that can be imported correctly:
 * [fmt](https://pkg.go.dev/fmt) (partially)
 * [reflect](https://pkg.go.dev/reflect) (partially)
 * [time](https://pkg.go.dev/time) (partially)
+* [encoding/binary](https://pkg.go.dev/encoding/binary)
+* [encoding/hex](https://pkg.go.dev/encoding/hex)
+* [encoding/base32](https://pkg.go.dev/encoding/base32)
+* [encoding/base64](https://pkg.go.dev/encoding/base64)
 * [regexp](https://pkg.go.dev/regexp)
 * [regexp/syntax](https://pkg.go.dev/regexp/syntax)
 
diff --git a/_cmptest/base64demo/base64.go b/_cmptest/base64demo/base64.go
new file mode 100644
index 00000000..0fbd1fa4
--- /dev/null
+++ b/_cmptest/base64demo/base64.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"encoding/base32"
+	"encoding/base64"
+	"encoding/hex"
+	"fmt"
+	"log"
+)
+
+func base64Demo() {
+	msg := "Hello, 世界"
+	encoded := base64.StdEncoding.EncodeToString([]byte(msg))
+	fmt.Println(encoded)
+	decoded, err := base64.StdEncoding.DecodeString(encoded)
+	if err != nil {
+		fmt.Println("decode error:", err)
+		return
+	}
+	fmt.Println(string(decoded))
+}
+
+func base32Demo() {
+	str := "JBSWY3DPFQQHO33SNRSCC==="
+	dst := make([]byte, base32.StdEncoding.DecodedLen(len(str)))
+	n, err := base32.StdEncoding.Decode(dst, []byte(str))
+	if err != nil {
+		fmt.Println("decode error:", err)
+		return
+	}
+	dst = dst[:n]
+	fmt.Printf("%q\n", dst)
+}
+
+func hexDemo() {
+	const s = "48656c6c6f20476f7068657221"
+	decoded, err := hex.DecodeString(s)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%s\n", decoded)
+
+}
+func main() {
+	base64Demo()
+	base32Demo()
+	hexDemo()
+}
diff --git a/ssa/expr.go b/ssa/expr.go
index 9400958a..263ebb7a 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -699,6 +699,7 @@ func (b Builder) ChangeType(t Type, x Expr) (ret Expr) {
 		case vkFuncDecl:
 			ret.impl = checkExpr(x, t.raw.Type, b).impl
 		case vkClosure:
+			// TODO(xsw): change type should be a noop instruction
 			convType := func() Expr {
 				r := Expr{llvm.CreateAlloca(b.impl, t.ll), b.Prog.Pointer(t)}
 				b.Store(r, x)