diff --git a/vendor/google.golang.org/protobuf/internal/impl/checkinit.go b/vendor/google.golang.org/protobuf/internal/impl/checkinit.go
new file mode 100644
index 0000000..b82341e
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/impl/checkinit.go
@@ -0,0 +1,141 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package impl
+
+import (
+	"sync"
+
+	"google.golang.org/protobuf/internal/errors"
+	pref "google.golang.org/protobuf/reflect/protoreflect"
+	piface "google.golang.org/protobuf/runtime/protoiface"
+)
+
+func (mi *MessageInfo) checkInitialized(in piface.CheckInitializedInput) (piface.CheckInitializedOutput, error) {
+	var p pointer
+	if ms, ok := in.Message.(*messageState); ok {
+		p = ms.pointer()
+	} else {
+		p = in.Message.(*messageReflectWrapper).pointer()
+	}
+	return piface.CheckInitializedOutput{}, mi.checkInitializedPointer(p)
+}
+
+func (mi *MessageInfo) checkInitializedPointer(p pointer) error {
+	mi.init()
+	if !mi.needsInitCheck {
+		return nil
+	}
+	if p.IsNil() {
+		for _, f := range mi.orderedCoderFields {
+			if f.isRequired {
+				return errors.RequiredNotSet(string(mi.Desc.Fields().ByNumber(f.num).FullName()))
+			}
+		}
+		return nil
+	}
+	if mi.extensionOffset.IsValid() {
+		e := p.Apply(mi.extensionOffset).Extensions()
+		if err := mi.isInitExtensions(e); err != nil {
+			return err
+		}
+	}
+	for _, f := range mi.orderedCoderFields {
+		if !f.isRequired && f.funcs.isInit == nil {
+			continue
+		}
+		fptr := p.Apply(f.offset)
+		if f.isPointer && fptr.Elem().IsNil() {
+			if f.isRequired {
+				return errors.RequiredNotSet(string(mi.Desc.Fields().ByNumber(f.num).FullName()))
+			}
+			continue
+		}
+		if f.funcs.isInit == nil {
+			continue
+		}
+		if err := f.funcs.isInit(fptr, f); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (mi *MessageInfo) isInitExtensions(ext *map[int32]ExtensionField) error {
+	if ext == nil {
+		return nil
+	}
+	for _, x := range *ext {
+		ei := getExtensionFieldInfo(x.Type())
+		if ei.funcs.isInit == nil {
+			continue
+		}
+		v := x.Value()
+		if !v.IsValid() {
+			continue
+		}
+		if err := ei.funcs.isInit(v); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+var (
+	needsInitCheckMu  sync.Mutex
+	needsInitCheckMap sync.Map
+)
+
+// needsInitCheck reports whether a message needs to be checked for partial initialization.
+//
+// It returns true if the message transitively includes any required or extension fields.
+func needsInitCheck(md pref.MessageDescriptor) bool {
+	if v, ok := needsInitCheckMap.Load(md); ok {
+		if has, ok := v.(bool); ok {
+			return has
+		}
+	}
+	needsInitCheckMu.Lock()
+	defer needsInitCheckMu.Unlock()
+	return needsInitCheckLocked(md)
+}
+
+func needsInitCheckLocked(md pref.MessageDescriptor) (has bool) {
+	if v, ok := needsInitCheckMap.Load(md); ok {
+		// If has is true, we've previously determined that this message
+		// needs init checks.
+		//
+		// If has is false, we've previously determined that it can never
+		// be uninitialized.
+		//
+		// If has is not a bool, we've just encountered a cycle in the
+		// message graph. In this case, it is safe to return false: If
+		// the message does have required fields, we'll detect them later
+		// in the graph traversal.
+		has, ok := v.(bool)
+		return ok && has
+	}
+	needsInitCheckMap.Store(md, struct{}{}) // avoid cycles while descending into this message
+	defer func() {
+		needsInitCheckMap.Store(md, has)
+	}()
+	if md.RequiredNumbers().Len() > 0 {
+		return true
+	}
+	if md.ExtensionRanges().Len() > 0 {
+		return true
+	}
+	for i := 0; i < md.Fields().Len(); i++ {
+		fd := md.Fields().Get(i)
+		// Map keys are never messages, so just consider the map value.
+		if fd.IsMap() {
+			fd = fd.MapValue()
+		}
+		fmd := fd.Message()
+		if fmd != nil && needsInitCheckLocked(fmd) {
+			return true
+		}
+	}
+	return false
+}