internal/impl: unexport ExtensionFieldV1.Value

CL/177620 modifies v1 to stop touching the Value field directly,
such that it is now unexport the Value field.

Change-Id: I0a05bbe59146862fc77c261349d7d90d6fa312e0
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/177621
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/cmd/protoc-gen-go-grpc/testdata/go.mod b/cmd/protoc-gen-go-grpc/testdata/go.mod
index f0260ae..44d8145 100644
--- a/cmd/protoc-gen-go-grpc/testdata/go.mod
+++ b/cmd/protoc-gen-go-grpc/testdata/go.mod
@@ -1,7 +1,7 @@
 module google.golang.org/protobuf/cmd/protoc-gen-go-grpc/testdata
 
 require (
-	github.com/golang/protobuf v1.2.1-0.20190515194842-7574ba03306e
+	github.com/golang/protobuf v1.2.1-0.20190516201927-a2cd3ac1b343
 	google.golang.org/grpc v1.19.0
 	google.golang.org/protobuf v1.0.0
 )
diff --git a/cmd/protoc-gen-go/testdata/go.mod b/cmd/protoc-gen-go/testdata/go.mod
index 7d3dea1..ee647c2 100644
--- a/cmd/protoc-gen-go/testdata/go.mod
+++ b/cmd/protoc-gen-go/testdata/go.mod
@@ -1,7 +1,7 @@
 module google.golang.org/protobuf/cmd/protoc-gen-go/testdata
 
 require (
-	github.com/golang/protobuf v1.2.1-0.20190515194842-7574ba03306e
+	github.com/golang/protobuf v1.2.1-0.20190516201927-a2cd3ac1b343
 	google.golang.org/protobuf v1.0.0
 )
 
diff --git a/go.mod b/go.mod
index 00d591f..1d12292 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,6 @@
 go 1.9
 
 require (
-	github.com/golang/protobuf v1.2.1-0.20190515194842-7574ba03306e
+	github.com/golang/protobuf v1.2.1-0.20190516201927-a2cd3ac1b343
 	github.com/google/go-cmp v0.3.0
 )
diff --git a/go.sum b/go.sum
index 8181df4..3a3456a 100644
--- a/go.sum
+++ b/go.sum
@@ -1,7 +1,9 @@
 github.com/golang/protobuf v1.2.1-0.20190514181236-7800af189d76/go.mod h1:Zfz6qcDoDBESdv6JsKsGpgNHnkvwJAJwcA9eL+mOkgc=
-github.com/golang/protobuf v1.2.1-0.20190515194842-7574ba03306e h1:wrd8ZnV3RJvrouZgfP+s3ZcAkX6J1PbrVFWchWHUz90=
 github.com/golang/protobuf v1.2.1-0.20190515194842-7574ba03306e/go.mod h1:GjgUz9uwrRQmdPBBrFqiVbojAmlpy6ryM6DCzC+20rE=
+github.com/golang/protobuf v1.2.1-0.20190516201927-a2cd3ac1b343 h1:7ggaFvChsnb7ONk6XaHOlWSUItKRmiaCuisgen9uhSg=
+github.com/golang/protobuf v1.2.1-0.20190516201927-a2cd3ac1b343/go.mod h1:PScGDF2x230A126tLt9Ol9RjhXzbiPJrt/CogooD2mE=
 github.com/google/go-cmp v0.3.0 h1:crn/baboCvb5fXaQ0IJ1SGTsTVrWpDsCWC8EGETZijY=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 google.golang.org/protobuf v0.0.0-20190514172829-e89e6244e0e8/go.mod h1:791zQGC15vDqjpmPRn1uGPu5oHy/Jzw/Q1n5JsgIIcY=
 google.golang.org/protobuf v0.0.0-20190514231807-cdb777356907/go.mod h1:HeRLsKXv4+wE27dOIGwnqcOgq6a1O/GJ7mGhiEPnBrU=
+google.golang.org/protobuf v0.0.0-20190516201745-40b83d67fc75/go.mod h1:jf+u8AHuKtkib+0J4/bQXPNzCmT3V9a02hVzYKtatuw=
diff --git a/internal/impl/legacy_extension.go b/internal/impl/legacy_extension.go
index f011192..47ccc45 100644
--- a/internal/impl/legacy_extension.go
+++ b/internal/impl/legacy_extension.go
@@ -258,15 +258,13 @@
 
 	// value is either the value of GetValue,
 	// or a *lazyExtensionValue that then returns the value of GetValue.
-	//
-	// TODO: unexport this.
-	Value interface{}
+	value interface{}
 }
 
 // HasValue reports whether a value is set for the extension field.
 // This may be called concurrently.
 func (f ExtensionFieldV1) HasValue() bool {
-	return f.Value != nil
+	return f.value != nil
 }
 
 // GetValue returns the concrete value for the extension field.
@@ -287,23 +285,23 @@
 //
 // TODO: switch interface{} to protoreflect.Value
 func (f ExtensionFieldV1) GetValue() interface{} {
-	if f, ok := f.Value.(*lazyExtensionValue); ok {
+	if f, ok := f.value.(*lazyExtensionValue); ok {
 		return f.GetValue()
 	}
-	return f.Value
+	return f.value
 }
 
 // SetEagerValue sets the current value of the extension.
 // This must not be called concurrently.
 func (f *ExtensionFieldV1) SetEagerValue(v interface{}) {
-	f.Value = v
+	f.value = v
 }
 
 // SetLazyValue sets a value that is to be lazily evaluated upon first use.
 // The returned value must not be nil.
 // This must not be called concurrently.
 func (f *ExtensionFieldV1) SetLazyValue(v func() interface{}) {
-	f.Value = &lazyExtensionValue{value: v}
+	f.value = &lazyExtensionValue{value: v}
 }
 
 type lazyExtensionValue struct {