wire: FieldsOf now provides a pointer to the field type as well as the actual field type (#209)

internal/wire/testdata/FieldsOfStruct/foo/foo.go

@@ -26,4 +26,5 @@ func provideS() S {
 
 func main() {
 	fmt.Println(injectedMessage())
+	fmt.Println("pointer to " + *injectedMessagePtr())
 }

internal/wire/testdata/FieldsOfStruct/foo/wire.go

@@ -26,3 +26,10 @@ func injectedMessage() string {
 		wire.FieldsOf(new(S), "Foo"))
 	return ""
 }
+
+func injectedMessagePtr() *string {
+	wire.Build(
+		provideS,
+		wire.FieldsOf(new(S), "Foo"))
+	return nil
+}

internal/wire/testdata/FieldsOfStruct/want/program_out.txt

@@ -1 +1,2 @@
 Hello, World!
+pointer to Hello, World!

internal/wire/testdata/FieldsOfStruct/want/wire_gen.go

@@ -12,3 +12,9 @@ func injectedMessage() string {
 	string2 := s.Foo
 	return string2
 }
+
+func injectedMessagePtr() *string {
+	s := provideS()
+	string2 := &s.Foo
+	return string2
+}