fix: bug when marshal nil interface{} that contains not-indirect value

internal/encoder/compiler.go

@@ -626,16 +626,16 @@ func (self *Compiler) compileStructFieldQuoted(p *ir.Program, sp int, vt reflect
 }
 
 func (self *Compiler) compileInterface(p *ir.Program, vt reflect.Type) {
-	x := p.PC()
-	p.Add(ir.OP_is_nil_p1)
-
 	/* iface and efaces are different */
 	if vt.NumMethod() == 0 {
 		p.Add(ir.OP_eface)
-	} else {
-		p.Add(ir.OP_iface)
+		return
 	}
 
+	x := p.PC()
+	p.Add(ir.OP_is_nil_p1)
+	p.Add(ir.OP_iface)
+
 	/* the "null" value */
 	e := p.PC()
 	p.Add(ir.OP_goto)

issue_test/common_test.go

@@ -28,4 +28,11 @@ func assertUnmarshal(t *testing.T, api sonic.API, input []byte, newfn func() int
 	jerr := json.Unmarshal(input, jv)
 	assert.Equal(t, jv, sv)
 	assert.Equal(t, serr == nil, jerr == nil)
-}
+}
+
+func assertMarshal(t *testing.T, api sonic.API, v interface{}) {
+	sout, serr := api.Marshal(&v)
+	jout, jerr := json.Marshal(&v)
+	assert.Equal(t, jerr == nil, serr == nil, jerr)
+	assert.Equal(t, jout, sout, v)
+}

issue_test/issue755_test.go

@@ -0,0 +1,41 @@
+package issue_test
+
+import (
+	"testing"
+	"github.com/bytedance/sonic"
+)
+
+func TestIssue755_NilEfaceWithDirectValue(t *testing.T) {
+	tests := []interface{} {
+		struct {
+			Foo *int
+		}{},
+		struct {
+			Foo func()
+		}{},
+		chan int(nil),
+	}
+	for _, v := range(tests) {
+		assertMarshal(t, sonic.ConfigDefault, v)
+	}
+}
+
+type NilMarshaler struct {}
+
+func (n *NilMarshaler) MarshalJSON() ([]byte, error) {
+	if n == nil {
+		return []byte(`"my null value"`), nil
+	}
+	return []byte(`{}`), nil
+}
+
+func TestIssue755_MarshalIface(t *testing.T) {
+	tests := []interface{} {
+		&NilMarshaler{},
+		(*NilMarshaler)(nil),
+	}
+	for _, v := range(tests) {
+		assertMarshal(t, sonic.ConfigDefault, v)
+	}
+}
+