diff --git a/go.mod b/go.mod
deleted file mode 100644
index dbcf032..0000000
--- a/go.mod
+++ /dev/null
@@ -1,3 +0,0 @@
-module github.com/golang/protobuf
-
-require github.com/golang/protobuf/v2 v2.0.0-20190320041633-559d47f1da45
diff --git a/go.sum b/go.sum
deleted file mode 100644
index d0211f0..0000000
--- a/go.sum
+++ /dev/null
@@ -1,5 +0,0 @@
-github.com/golang/protobuf v1.2.1-0.20190311233832-968e039ade03/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
-github.com/golang/protobuf/v2 v2.0.0-20190320041633-559d47f1da45 h1:UpSQcE2BQjlwjgUj1o+22OMRLUpeeTZNH1fuZN5lEv4=
-github.com/golang/protobuf/v2 v2.0.0-20190320041633-559d47f1da45/go.mod h1:memx26heJzlbv0kkl0yZyY1iCWPnh53PDfstsy8HCEg=
-github.com/google/go-cmp v0.2.1-0.20190312032427-6f77996f0c42 h1:q3pnF5JFBNRz8sRD+IRj7Y6DMyYGTNqnZ9axTbSfoNI=
-github.com/google/go-cmp v0.2.1-0.20190312032427-6f77996f0c42/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
diff --git a/internal/proto/common.go b/internal/proto/common.go
index d49c17c..93f5178 100644
--- a/internal/proto/common.go
+++ b/internal/proto/common.go
@@ -9,12 +9,11 @@
 // that they would otherwise be able to call directly.
 
 import (
-	"github.com/golang/protobuf/protoapi"
-
+	"github.com/golang/protobuf/v2/runtime/protoiface"
 	_ "github.com/golang/protobuf/v2/runtime/protolegacy"
 )
 
 type (
-	Message       = protoapi.Message
-	ExtensionDesc = protoapi.ExtensionDesc
+	Message       = protoiface.MessageV1
+	ExtensionDesc = protoiface.ExtensionDescV1
 )
diff --git a/proto/clone.go b/proto/clone.go
index 5f97f7a..2cb7009 100644
--- a/proto/clone.go
+++ b/proto/clone.go
@@ -13,7 +13,6 @@
 	"reflect"
 	"strings"
 
-	"github.com/golang/protobuf/protoapi"
 	"github.com/golang/protobuf/v2/reflect/protoreflect"
 )
 
@@ -209,7 +208,7 @@
 	}
 }
 
-func mergeExtension(out, in protoapi.ExtensionFields) {
+func mergeExtension(out, in extensionFields) {
 	in.Range(func(extNum protoreflect.FieldNumber, eIn Extension) bool {
 		eOut := Extension{Desc: eIn.Desc}
 		if eIn.Value != nil {
diff --git a/proto/deprecated.go b/proto/deprecated.go
index da5b374..7db76d4 100644
--- a/proto/deprecated.go
+++ b/proto/deprecated.go
@@ -5,49 +5,69 @@
 package proto
 
 import (
+	"encoding/json"
 	"errors"
-
-	"github.com/golang/protobuf/protoapi"
+	"fmt"
+	"strconv"
 )
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 var ErrInternalBadWireType = errors.New("proto: internal error: bad wiretype for oneof")
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 type Stats struct{ Emalloc, Dmalloc, Encode, Decode, Chit, Cmiss, Size uint64 }
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 func GetStats() Stats { return Stats{} }
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 func MarshalMessageSet(interface{}) ([]byte, error) {
 	return nil, errors.New("proto: not implemented")
 }
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 func UnmarshalMessageSet([]byte, interface{}) error {
 	return errors.New("proto: not implemented")
 }
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 func MarshalMessageSetJSON(interface{}) ([]byte, error) {
 	return nil, errors.New("proto: not implemented")
 }
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 func UnmarshalMessageSetJSON([]byte, interface{}) error {
 	return errors.New("proto: not implemented")
 }
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 func RegisterMessageSetType(Message, int32, string) {}
 
-// Deprecated: do not use.
+// Deprecated: Do not use.
 func EnumName(m map[int32]string, v int32) string {
-	return protoapi.EnumName(m, v)
+	if s, ok := m[v]; ok {
+		return s
+	}
+	return strconv.Itoa(int(v))
 }
 
-// Deprecated: do not use.
-func UnmarshalJSONEnum(m map[string]int32, data []byte, enumName string) (int32, error) {
-	return protoapi.UnmarshalJSONEnum(m, data, enumName)
+// Deprecated: Do not use.
+func UnmarshalJSONEnum(m map[string]int32, b []byte, enumName string) (int32, error) {
+	if b[0] == '"' {
+		var s string
+		if err := json.Unmarshal(b, &s); err != nil {
+			return 0, fmt.Errorf("proto: invalid input for enum %v: %s", enumName, b)
+		}
+		v, ok := m[s]
+		if !ok {
+			return 0, fmt.Errorf("proto: invalid value for enum %v: %s", enumName, b)
+		}
+		return v, nil
+	} else {
+		var v int32
+		if err := json.Unmarshal(b, &v); err != nil {
+			return 0, fmt.Errorf("proto: invalid input for enum %v: %s", enumName, b)
+		}
+		return v, nil
+	}
 }
diff --git a/proto/equal.go b/proto/equal.go
index 29ae49b..04da80a 100644
--- a/proto/equal.go
+++ b/proto/equal.go
@@ -12,8 +12,8 @@
 	"reflect"
 	"strings"
 
-	"github.com/golang/protobuf/protoapi"
 	"github.com/golang/protobuf/v2/reflect/protoreflect"
+	"github.com/golang/protobuf/v2/runtime/protoimpl"
 )
 
 /*
@@ -94,8 +94,8 @@
 
 	if em1 := v1.FieldByName("XXX_InternalExtensions"); em1.IsValid() {
 		em2 := v2.FieldByName("XXX_InternalExtensions")
-		m1 := protoapi.ExtensionFieldsOf(em1.Addr().Interface())
-		m2 := protoapi.ExtensionFieldsOf(em2.Addr().Interface())
+		m1 := protoimpl.X.ExtensionFieldsOf(em1.Addr().Interface())
+		m2 := protoimpl.X.ExtensionFieldsOf(em2.Addr().Interface())
 		if !equalExtensions(v1.Type(), m1, m2) {
 			return false
 		}
@@ -103,8 +103,8 @@
 
 	if em1 := v1.FieldByName("XXX_extensions"); em1.IsValid() {
 		em2 := v2.FieldByName("XXX_extensions")
-		m1 := protoapi.ExtensionFieldsOf(em1.Addr().Interface())
-		m2 := protoapi.ExtensionFieldsOf(em2.Addr().Interface())
+		m1 := protoimpl.X.ExtensionFieldsOf(em1.Addr().Interface())
+		m2 := protoimpl.X.ExtensionFieldsOf(em2.Addr().Interface())
 		if !equalExtensions(v1.Type(), m1, m2) {
 			return false
 		}
@@ -207,7 +207,7 @@
 	return false
 }
 
-func equalExtensions(base reflect.Type, em1, em2 protoapi.ExtensionFields) bool {
+func equalExtensions(base reflect.Type, em1, em2 extensionFields) bool {
 	if em1.Len() != em2.Len() {
 		return false
 	}
diff --git a/proto/extensions.go b/proto/extensions.go
index 3923707..836619d 100644
--- a/proto/extensions.go
+++ b/proto/extensions.go
@@ -15,14 +15,15 @@
 	"reflect"
 	"sync"
 
-	"github.com/golang/protobuf/protoapi"
 	"github.com/golang/protobuf/v2/reflect/protoreflect"
+	"github.com/golang/protobuf/v2/runtime/protoiface"
+	"github.com/golang/protobuf/v2/runtime/protoimpl"
 )
 
 // ErrMissingExtension is the error returned by GetExtension if the named extension is not in the message.
 var ErrMissingExtension = errors.New("proto: missing extension")
 
-func extendable(p interface{}) (protoapi.ExtensionFields, error) {
+func extendable(p interface{}) (extensionFields, error) {
 	type extendableProto interface {
 		Message
 		ExtensionRangeArray() []ExtensionRange
@@ -32,10 +33,10 @@
 		if v.Kind() == reflect.Ptr && !v.IsNil() {
 			v = v.Elem()
 			if v := v.FieldByName("XXX_InternalExtensions"); v.IsValid() {
-				return protoapi.ExtensionFieldsOf(v.Addr().Interface()), nil
+				return protoimpl.X.ExtensionFieldsOf(v.Addr().Interface()), nil
 			}
 			if v := v.FieldByName("XXX_extensions"); v.IsValid() {
-				return protoapi.ExtensionFieldsOf(v.Addr().Interface()), nil
+				return protoimpl.X.ExtensionFieldsOf(v.Addr().Interface()), nil
 			}
 		}
 	}
@@ -47,10 +48,10 @@
 var errNotExtendable = errors.New("proto: not an extendable proto.Message")
 
 type (
-	ExtensionRange         = protoapi.ExtensionRange
-	ExtensionDesc          = protoapi.ExtensionDesc
-	Extension              = protoapi.ExtensionField
-	XXX_InternalExtensions = protoapi.XXX_InternalExtensions
+	ExtensionRange         = protoiface.ExtensionRangeV1
+	ExtensionDesc          = protoiface.ExtensionDescV1
+	Extension              = protoimpl.ExtensionFieldV1
+	XXX_InternalExtensions = protoimpl.ExtensionFieldsV1
 )
 
 func isRepeatedExtension(ed *ExtensionDesc) bool {
diff --git a/proto/lib.go b/proto/lib.go
index 1906a2a..e82e138 100644
--- a/proto/lib.go
+++ b/proto/lib.go
@@ -15,13 +15,25 @@
 	"strconv"
 	"sync"
 
-	// Add a bogus dependency on the v2 API to ensure the Go toolchain does not
-	// remove our dependency from the go.mod file.
-	_ "github.com/golang/protobuf/v2/reflect/protoreflect"
-
-	"github.com/golang/protobuf/protoapi"
+	"github.com/golang/protobuf/v2/reflect/protoreflect"
+	"github.com/golang/protobuf/v2/runtime/protoiface"
+	"github.com/golang/protobuf/v2/runtime/protoimpl"
 )
 
+type extensionFields = interface {
+	Len() int
+	Has(protoreflect.FieldNumber) bool
+	Get(protoreflect.FieldNumber) protoimpl.ExtensionFieldV1
+	Set(protoreflect.FieldNumber, protoimpl.ExtensionFieldV1)
+	Clear(protoreflect.FieldNumber)
+	Range(f func(protoreflect.FieldNumber, protoimpl.ExtensionFieldV1) bool)
+
+	// HasInit and Locker are used by v1 GetExtension to provide
+	// an artificial degree of concurrent safety.
+	HasInit() bool
+	sync.Locker
+}
+
 // RequiredNotSetError is an error type returned by either Marshal or Unmarshal.
 // Marshal reports this when a required field is not initialized.
 // Unmarshal reports this when a required field is missing from the wire data.
@@ -84,7 +96,7 @@
 }
 
 // Message is implemented by generated protocol buffer messages.
-type Message = protoapi.Message
+type Message = protoiface.MessageV1
 
 var protoMessageType = reflect.TypeOf((*Message)(nil)).Elem()
 
diff --git a/proto/message_set.go b/proto/message_set.go
index 19a1a00..2878bdf 100644
--- a/proto/message_set.go
+++ b/proto/message_set.go
@@ -11,8 +11,8 @@
 import (
 	"errors"
 
-	"github.com/golang/protobuf/protoapi"
 	"github.com/golang/protobuf/v2/reflect/protoreflect"
+	"github.com/golang/protobuf/v2/runtime/protoimpl"
 )
 
 // errNoMessageTypeID occurs when a protocol buffer does not have a message type ID.
@@ -118,7 +118,7 @@
 // unmarshalMessageSet decodes the extension map encoded in buf in the message set wire format.
 // It is called by Unmarshal methods on protocol buffer messages with the message_set_wire_format option.
 func unmarshalMessageSet(buf []byte, exts interface{}) error {
-	m := protoapi.ExtensionFieldsOf(exts)
+	m := protoimpl.X.ExtensionFieldsOf(exts)
 
 	ms := new(messageSet)
 	if err := Unmarshal(buf, ms); err != nil {
diff --git a/proto/table_marshal.go b/proto/table_marshal.go
index aefee64..303c1ea 100644
--- a/proto/table_marshal.go
+++ b/proto/table_marshal.go
@@ -16,8 +16,8 @@
 	"sync/atomic"
 	"unicode/utf8"
 
-	"github.com/golang/protobuf/protoapi"
 	"github.com/golang/protobuf/v2/reflect/protoreflect"
+	"github.com/golang/protobuf/v2/runtime/protoimpl"
 )
 
 // a sizer takes a pointer to a field and the size of its tag, computes the size of
@@ -2366,7 +2366,7 @@
 
 // sizeExtensions computes the size of encoded data for a XXX_InternalExtensions field.
 func (u *marshalInfo) sizeExtensions(ext *XXX_InternalExtensions) int {
-	m := protoapi.ExtensionFieldsOf(ext)
+	m := protoimpl.X.ExtensionFieldsOf(ext)
 	if !m.HasInit() {
 		return 0
 	}
@@ -2395,7 +2395,7 @@
 
 // appendExtensions marshals a XXX_InternalExtensions field to the end of byte slice b.
 func (u *marshalInfo) appendExtensions(b []byte, ext *XXX_InternalExtensions, deterministic bool) ([]byte, error) {
-	m := protoapi.ExtensionFieldsOf(ext)
+	m := protoimpl.X.ExtensionFieldsOf(ext)
 	if !m.HasInit() {
 		return b, nil
 	}
@@ -2475,7 +2475,7 @@
 // sizeMessageSet computes the size of encoded data for a XXX_InternalExtensions field
 // in message set format (above).
 func (u *marshalInfo) sizeMessageSet(ext *XXX_InternalExtensions) int {
-	m := protoapi.ExtensionFieldsOf(ext)
+	m := protoimpl.X.ExtensionFieldsOf(ext)
 	if !m.HasInit() {
 		return 0
 	}
@@ -2511,7 +2511,7 @@
 // appendMessageSet marshals a XXX_InternalExtensions field in message set format (above)
 // to the end of byte slice b.
 func (u *marshalInfo) appendMessageSet(b []byte, ext *XXX_InternalExtensions, deterministic bool) ([]byte, error) {
-	m := protoapi.ExtensionFieldsOf(ext)
+	m := protoimpl.X.ExtensionFieldsOf(ext)
 	if !m.HasInit() {
 		return b, nil
 	}
diff --git a/proto/table_unmarshal.go b/proto/table_unmarshal.go
index 104f375..ae4395f 100644
--- a/proto/table_unmarshal.go
+++ b/proto/table_unmarshal.go
@@ -16,8 +16,8 @@
 	"sync/atomic"
 	"unicode/utf8"
 
-	"github.com/golang/protobuf/protoapi"
 	"github.com/golang/protobuf/v2/reflect/protoreflect"
+	"github.com/golang/protobuf/v2/runtime/protoimpl"
 )
 
 // Unmarshal is the entry point from the generated .pb.go files.
@@ -187,20 +187,20 @@
 		// Keep unrecognized data around.
 		// maybe in extensions, maybe in the unrecognized field.
 		z := m.offset(u.unrecognized).toBytes()
-		var emap protoapi.ExtensionFields
+		var emap extensionFields
 		var e Extension
 		for _, r := range u.extensionRanges {
 			if uint64(r.Start) <= tag && tag <= uint64(r.End) {
 				if u.extensions.IsValid() {
 					mp := m.offset(u.extensions).toExtensions()
-					emap = protoapi.ExtensionFieldsOf(mp)
+					emap = protoimpl.X.ExtensionFieldsOf(mp)
 					e = emap.Get(protoreflect.FieldNumber(tag))
 					z = &e.Raw
 					break
 				}
 				if u.oldExtensions.IsValid() {
 					p := m.offset(u.oldExtensions).toOldExtensions()
-					emap = protoapi.ExtensionFieldsOf(p)
+					emap = protoimpl.X.ExtensionFieldsOf(p)
 					e = emap.Get(protoreflect.FieldNumber(tag))
 					z = &e.Raw
 					break
diff --git a/proto/text.go b/proto/text.go
index ad0652b..dfd3e92 100644
--- a/proto/text.go
+++ b/proto/text.go
@@ -19,7 +19,6 @@
 	"sort"
 	"strings"
 
-	"github.com/golang/protobuf/protoapi"
 	"github.com/golang/protobuf/v2/reflect/protoreflect"
 )
 
@@ -817,7 +816,3 @@
 
 // CompactTextString is the same as CompactText, but returns the string directly.
 func CompactTextString(pb Message) string { return compactTextMarshaler.Text(pb) }
-
-func init() {
-	protoapi.CompactTextString = CompactTextString
-}
diff --git a/protoapi/api.go b/protoapi/api.go
deleted file mode 100644
index 1cae07b..0000000
--- a/protoapi/api.go
+++ /dev/null
@@ -1,242 +0,0 @@
-// Copyright 2018 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 protoapi contains the set of types referenced by generated messages.
-//
-// WARNING: This package should only ever be imported by generated messages.
-// The compatibility agreement covers nothing except for functionality needed
-// to keep existing generated messages operational.
-package protoapi
-
-import (
-	"fmt"
-	"sync"
-
-	"github.com/golang/protobuf/v2/reflect/protoreflect"
-)
-
-// TODO: How to handle Registration during the v1 to v2 switchover?
-
-type (
-	Message interface {
-		Reset()
-		String() string
-		ProtoMessage()
-	}
-
-	ExtensionRange struct {
-		Start, End int32 // both inclusive
-	}
-
-	ExtensionDesc struct {
-		// Type is the descriptor type for the extension field using the v2 API.
-		// If populated, the information in this field takes precedence over
-		// all other fields in ExtensionDesc.
-		Type protoreflect.ExtensionType
-
-		// ExtendedType is a typed nil-pointer to the parent message type that
-		// is being extended. It is possible for this to be unpopulated in v2
-		// since the message may no longer implement the v1 Message interface.
-		//
-		// Deprecated: Use Type.ExtendedType instead.
-		ExtendedType Message
-
-		// ExtensionType is zero value of the extension type.
-		//
-		// For historical reasons, reflect.TypeOf(ExtensionType) and Type.GoType
-		// may not be identical:
-		//	* for scalars (except []byte), where ExtensionType uses *T,
-		//	while Type.GoType uses T.
-		//	* for repeated fields, where ExtensionType uses []T,
-		//	while Type.GoType uses *[]T.
-		//
-		// Deprecated: Use Type.GoType instead.
-		ExtensionType interface{}
-
-		// Field is the field number of the extension.
-		//
-		// Deprecated: Use Type.Number instead.
-		Field int32 // field number
-
-		// Name is the fully qualified name of extension.
-		//
-		// Deprecated: Use Type.FullName instead.
-		Name string
-
-		// Tag is the protobuf struct tag used in the v1 API.
-		//
-		// Deprecated: Do not use.
-		Tag string
-
-		// Filename is the proto filename in which the extension is defined.
-		//
-		// Deprecated: Use Type.Parent to ascend to the top-most parent and use
-		// protoreflect.FileDescriptor.Path.
-		Filename string
-	}
-
-	ExtensionFields        extensionFields
-	ExtensionField         extensionField
-	XXX_InternalExtensions extensionSyncMap
-)
-
-// ExtensionFieldsOf returns an ExtensionFields abstraction over various
-// internal representations of extension fields.
-func ExtensionFieldsOf(p interface{}) ExtensionFields {
-	switch p := p.(type) {
-	case *map[int32]ExtensionField:
-		return (*extensionMap)(p)
-	case *XXX_InternalExtensions:
-		return (*extensionSyncMap)(p)
-	default:
-		panic(fmt.Sprintf("invalid extension fields type: %T", p))
-	}
-}
-
-type extensionFields interface {
-	Len() int
-	Has(protoreflect.FieldNumber) bool
-	Get(protoreflect.FieldNumber) ExtensionField
-	Set(protoreflect.FieldNumber, ExtensionField)
-	Clear(protoreflect.FieldNumber)
-	Range(f func(protoreflect.FieldNumber, ExtensionField) bool)
-
-	// HasInit and Locker are used by v1 GetExtension to provide
-	// an artificial degree of concurrent safety.
-	HasInit() bool
-	sync.Locker
-}
-
-type extensionField struct {
-	// When an extension is stored in a message using SetExtension
-	// only desc and value are set. When the message is marshaled
-	// Raw will be set to the encoded form of the message.
-	//
-	// When a message is unmarshaled and contains extensions, each
-	// extension will have only Raw set. When such an extension is
-	// accessed using GetExtension (or GetExtensions) desc and value
-	// will be set.
-	Desc *ExtensionDesc // TODO: switch to protoreflect.ExtensionType
-
-	// Value is a concrete value for the extension field. Let the type of
-	// Desc.ExtensionType be the "API type" and the type of Value be the
-	// "storage type". The API type and storage type are the same except:
-	//	* for scalars (except []byte), where the API type uses *T,
-	//	while the storage type uses T.
-	//	* for repeated fields, where the API type uses []T,
-	//	while the storage type uses *[]T.
-	//
-	// The reason for the divergence is so that the storage type more naturally
-	// matches what is expected of when retrieving the values through the
-	// protobuf reflection APIs.
-	//
-	// The Value may only be populated if Desc is also populated.
-	Value interface{} // TODO: switch to protoreflect.Value
-
-	// Raw is the raw encoded bytes for the extension field.
-	// It is possible for Raw to be populated irrespective of whether the
-	// other fields are populated.
-	Raw []byte // TODO: switch to protoreflect.RawFields
-}
-
-type extensionSyncMap struct {
-	p *struct {
-		mu sync.Mutex
-		m  extensionMap
-	}
-}
-
-func (m extensionSyncMap) Len() int {
-	if m.p == nil {
-		return 0
-	}
-	return m.p.m.Len()
-}
-func (m extensionSyncMap) Has(n protoreflect.FieldNumber) bool {
-	if m.p == nil {
-		return false
-	}
-	return m.p.m.Has(n)
-}
-func (m extensionSyncMap) Get(n protoreflect.FieldNumber) ExtensionField {
-	if m.p == nil {
-		return ExtensionField{}
-	}
-	return m.p.m.Get(n)
-}
-func (m *extensionSyncMap) Set(n protoreflect.FieldNumber, x ExtensionField) {
-	if m.p == nil {
-		m.p = new(struct {
-			mu sync.Mutex
-			m  extensionMap
-		})
-	}
-	m.p.m.Set(n, x)
-}
-func (m extensionSyncMap) Clear(n protoreflect.FieldNumber) {
-	if m.p == nil {
-		return
-	}
-	m.p.m.Clear(n)
-}
-func (m extensionSyncMap) Range(f func(protoreflect.FieldNumber, ExtensionField) bool) {
-	if m.p == nil {
-		return
-	}
-	m.p.m.Range(f)
-}
-
-func (m extensionSyncMap) HasInit() bool {
-	return m.p != nil
-}
-func (m extensionSyncMap) Lock() {
-	m.p.mu.Lock()
-}
-func (m extensionSyncMap) Unlock() {
-	m.p.mu.Unlock()
-}
-
-type extensionMap map[int32]ExtensionField
-
-func (m extensionMap) Len() int {
-	return len(m)
-}
-func (m extensionMap) Has(n protoreflect.FieldNumber) bool {
-	_, ok := m[int32(n)]
-	return ok
-}
-func (m extensionMap) Get(n protoreflect.FieldNumber) ExtensionField {
-	return m[int32(n)]
-}
-func (m *extensionMap) Set(n protoreflect.FieldNumber, x ExtensionField) {
-	if *m == nil {
-		*m = make(map[int32]ExtensionField)
-	}
-	(*m)[int32(n)] = x
-}
-func (m *extensionMap) Clear(n protoreflect.FieldNumber) {
-	delete(*m, int32(n))
-}
-func (m extensionMap) Range(f func(protoreflect.FieldNumber, ExtensionField) bool) {
-	for n, x := range m {
-		if !f(protoreflect.FieldNumber(n), x) {
-			return
-		}
-	}
-}
-
-var globalLock sync.Mutex
-
-func (m extensionMap) HasInit() bool {
-	return m != nil
-}
-func (m extensionMap) Lock() {
-	if !m.HasInit() {
-		panic("cannot lock an uninitialized map")
-	}
-	globalLock.Lock()
-}
-func (m extensionMap) Unlock() {
-	globalLock.Unlock()
-}
diff --git a/protoapi/impl.go b/protoapi/impl.go
deleted file mode 100644
index 460b592..0000000
--- a/protoapi/impl.go
+++ /dev/null
@@ -1,91 +0,0 @@
-// Copyright 2018 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 protoapi
-
-import (
-	"encoding/binary"
-	"encoding/json"
-	"fmt"
-	"hash/crc32"
-	"math"
-	"strconv"
-)
-
-// TODO: Are these the final signatures that we want?
-
-// EnumName is a helper function to simplify printing protocol buffer enums
-// by name.  Given an enum map and a value, it returns a useful string.
-func EnumName(m map[int32]string, v int32) string {
-	s, ok := m[v]
-	if ok {
-		return s
-	}
-	return strconv.Itoa(int(v))
-}
-
-// UnmarshalJSONEnum is a helper function to simplify recovering enum int values
-// from their JSON-encoded representation. Given a map from the enum's symbolic
-// names to its int values, and a byte buffer containing the JSON-encoded
-// value, it returns an int32 that can be cast to the enum type by the caller.
-//
-// The function can deal with both JSON representations, numeric and symbolic.
-func UnmarshalJSONEnum(m map[string]int32, data []byte, enumName string) (int32, error) {
-	if data[0] == '"' {
-		// New style: enums are strings.
-		var repr string
-		if err := json.Unmarshal(data, &repr); err != nil {
-			return -1, err
-		}
-		val, ok := m[repr]
-		if !ok {
-			return 0, fmt.Errorf("unrecognized enum %s value %q", enumName, repr)
-		}
-		return val, nil
-	}
-	// Old style: enums are ints.
-	var val int32
-	if err := json.Unmarshal(data, &val); err != nil {
-		return 0, fmt.Errorf("cannot unmarshal %#q into enum %s", data, enumName)
-	}
-	return val, nil
-}
-
-// CompressGZIP compresses the input as a GZIP-encoded file.
-// The current implementation does no compression.
-func CompressGZIP(in []byte) (out []byte) {
-	// RFC 1952, section 2.3.1.
-	var gzipHeader = [10]byte{0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff}
-
-	// RFC 1951, section 3.2.4.
-	var blockHeader [5]byte
-	const maxBlockSize = math.MaxUint16
-	numBlocks := 1 + len(in)/maxBlockSize
-
-	// RFC 1952, section 2.3.1.
-	var gzipFooter [8]byte
-	binary.LittleEndian.PutUint32(gzipFooter[0:4], crc32.ChecksumIEEE(in))
-	binary.LittleEndian.PutUint32(gzipFooter[4:8], uint32(len(in)))
-
-	// Encode the input without compression using raw DEFLATE blocks.
-	out = make([]byte, 0, len(gzipHeader)+len(blockHeader)*numBlocks+len(in)+len(gzipFooter))
-	out = append(out, gzipHeader[:]...)
-	for blockHeader[0] == 0 {
-		blockSize := maxBlockSize
-		if blockSize > len(in) {
-			blockHeader[0] = 0x01 // final bit per RFC 1951, section 3.2.3.
-			blockSize = len(in)
-		}
-		binary.LittleEndian.PutUint16(blockHeader[1:3], uint16(blockSize)^0x0000)
-		binary.LittleEndian.PutUint16(blockHeader[3:5], uint16(blockSize)^0xffff)
-		out = append(out, blockHeader[:]...)
-		out = append(out, in[:blockSize]...)
-		in = in[blockSize:]
-	}
-	out = append(out, gzipFooter[:]...)
-	return out
-}
-
-// TODO: Remove this when v2 textpb is available.
-var CompactTextString func(Message) string
diff --git a/protoapi/impl_test.go b/protoapi/impl_test.go
deleted file mode 100644
index bc73ed7..0000000
--- a/protoapi/impl_test.go
+++ /dev/null
@@ -1,41 +0,0 @@
-// 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 protoapi
-
-import (
-	"bytes"
-	"compress/gzip"
-	"io/ioutil"
-	"math"
-	"strings"
-	"testing"
-)
-
-func TestCompressGZIP(t *testing.T) {
-	tests := []string{
-		"",
-		"a",
-		"ab",
-		"abc",
-		strings.Repeat("a", math.MaxUint16-1),
-		strings.Repeat("b", math.MaxUint16),
-		strings.Repeat("c", math.MaxUint16+1),
-		strings.Repeat("abcdefghijklmnopqrstuvwxyz", math.MaxUint16-13),
-	}
-	for _, want := range tests {
-		rb := bytes.NewReader(CompressGZIP([]byte(want)))
-		zr, err := gzip.NewReader(rb)
-		if err != nil {
-			t.Errorf("unexpected gzip.NewReader error: %v", err)
-		}
-		b, err := ioutil.ReadAll(zr)
-		if err != nil {
-			t.Errorf("unexpected ioutil.ReadAll error: %v", err)
-		}
-		if got := string(b); got != want {
-			t.Errorf("output mismatch: got %q, want %q", got, want)
-		}
-	}
-}