diff --git a/pkg/compiler/codegen.go b/pkg/compiler/codegen.go
index f1d84e211..ada41de1a 100644
--- a/pkg/compiler/codegen.go
+++ b/pkg/compiler/codegen.go
@@ -18,6 +18,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
 	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
+	"golang.org/x/tools/go/loader"
 )
 
 // The identifier of the entry function. Default set to Main.
@@ -1240,23 +1241,12 @@ func (c *codegen) newFunc(decl *ast.FuncDecl) *funcScope {
 	return f
 }
 
-// CodeGen compiles the program to bytecode.
-func CodeGen(info *buildInfo) ([]byte, error) {
-	pkg := info.program.Package(info.initialPackage)
-	c := &codegen{
-		buildInfo: info,
-		prog:      io.NewBufBinWriter(),
-		l:         []int{},
-		funcs:     map[string]*funcScope{},
-		labels:    map[labelWithType]uint16{},
-		typeInfo:  &pkg.Info,
-	}
-
+func (c *codegen) compile(info *buildInfo, pkg *loader.PackageInfo) error {
 	// Resolve the entrypoint of the program.
 	main, mainFile := resolveEntryPoint(mainIdent, pkg)
 	if main == nil {
 		c.prog.Err = fmt.Errorf("could not find func main. Did you forget to declare it? ")
-		return []byte{}, c.prog.Err
+		return c.prog.Err
 	}
 
 	funUsage := analyzeFuncUsage(info.program.AllPackages)
@@ -1297,9 +1287,29 @@ func CodeGen(info *buildInfo) ([]byte, error) {
 		}
 	}
 
-	if c.prog.Err != nil {
-		return nil, c.prog.Err
+	return c.prog.Err
+}
+
+func newCodegen(info *buildInfo, pkg *loader.PackageInfo) *codegen {
+	return &codegen{
+		buildInfo: info,
+		prog:      io.NewBufBinWriter(),
+		l:         []int{},
+		funcs:     map[string]*funcScope{},
+		labels:    map[labelWithType]uint16{},
+		typeInfo:  &pkg.Info,
 	}
+}
+
+// CodeGen compiles the program to bytecode.
+func CodeGen(info *buildInfo) ([]byte, error) {
+	pkg := info.program.Package(info.initialPackage)
+	c := newCodegen(info, pkg)
+
+	if err := c.compile(info, pkg); err != nil {
+		return nil, err
+	}
+
 	buf := c.prog.Bytes()
 	if err := c.writeJumps(buf); err != nil {
 		return nil, err
diff --git a/pkg/compiler/compiler.go b/pkg/compiler/compiler.go
index 91fc072c6..40cae382d 100644
--- a/pkg/compiler/compiler.go
+++ b/pkg/compiler/compiler.go
@@ -31,10 +31,9 @@ type buildInfo struct {
 	program        *loader.Program
 }
 
-// Compile compiles a Go program into bytecode that can run on the NEO virtual machine.
-func Compile(r io.Reader) ([]byte, error) {
+func getBuildInfo(src interface{}) (*buildInfo, error) {
 	conf := loader.Config{ParserMode: parser.ParseComments}
-	f, err := conf.ParseFile("", r)
+	f, err := conf.ParseFile("", src)
 	if err != nil {
 		return nil, err
 	}
@@ -45,9 +44,17 @@ func Compile(r io.Reader) ([]byte, error) {
 		return nil, err
 	}
 
-	ctx := &buildInfo{
+	return &buildInfo{
 		initialPackage: f.Name.Name,
 		program:        prog,
+	}, nil
+}
+
+// Compile compiles a Go program into bytecode that can run on the NEO virtual machine.
+func Compile(r io.Reader) ([]byte, error) {
+	ctx, err := getBuildInfo(r)
+	if err != nil {
+		return nil, err
 	}
 
 	buf, err := CodeGen(ctx)
diff --git a/pkg/compiler/debug_test.go b/pkg/compiler/debug_test.go
index f98493077..25b2b157f 100644
--- a/pkg/compiler/debug_test.go
+++ b/pkg/compiler/debug_test.go
@@ -4,8 +4,66 @@ import (
 	"testing"
 
 	"github.com/nspcc-dev/neo-go/pkg/internal/testserdes"
+	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
+func TestCodeGen_DebugInfo(t *testing.T) {
+	src := `package foo
+func Main(op string) bool {
+	res := methodInt(op)
+	_ = methodString()	
+	_ = methodByteArray()
+	_ = methodArray()
+	_ = methodStruct()
+	return res == 42
+}
+
+func methodInt(a string) int {
+	if a == "get42" {
+		return 42
+	}
+	return 3
+}
+func methodString() string { return "" }
+func methodByteArray() []byte { return nil }
+func methodArray() []bool { return nil }
+func methodStruct() struct{} { return struct{}{} }
+`
+
+	info, err := getBuildInfo(src)
+	require.NoError(t, err)
+
+	pkg := info.program.Package(info.initialPackage)
+	c := newCodegen(info, pkg)
+	require.NoError(t, c.compile(info, pkg))
+
+	buf := c.prog.Bytes()
+	d := c.emitDebugInfo()
+	require.NotNil(t, d)
+
+	t.Run("return types", func(t *testing.T) {
+		returnTypes := map[string]string{
+			"methodInt":    "Integer",
+			"methodString": "String", "methodByteArray": "ByteArray",
+			"methodArray": "Array", "methodStruct": "Struct",
+			"Main": "Boolean",
+		}
+		for i := range d.Methods {
+			name := d.Methods[i].Name.Name
+			assert.Equal(t, returnTypes[name], d.Methods[i].ReturnType)
+		}
+	})
+
+	// basic check that last instruction of every method is indeed RET
+	for i := range d.Methods {
+		index := d.Methods[i].Range.End
+		require.True(t, int(index) < len(buf))
+		require.EqualValues(t, opcode.RET, buf[index])
+	}
+}
+
 func TestDebugInfo_MarshalJSON(t *testing.T) {
 	d := &DebugInfo{
 		EntryPoint: "main",