Change .submsg_mut() to return $Msg$Mut instead of FieldEntry<$Msg$>.

PiperOrigin-RevId: 615849358

rust/test/shared/accessors_test.rs

@@ -524,7 +524,7 @@ fn test_message_opt_set() {
     assert_that!(msg.optional_nested_message_opt().is_set(), eq(true));
 
     msg.clear_optional_nested_message();
-    assert_that!(msg.optional_nested_message_mut().is_set(), eq(false));
+    assert_that!(msg.optional_nested_message_opt().is_set(), eq(false));
 }
 
 #[test]
@@ -532,28 +532,27 @@ fn test_setting_submsg() {
     let mut msg = TestAllTypes::new();
     let submsg = TestAllTypes_::NestedMessage::new();
 
-    let fieldentry = msg.optional_nested_message_mut();
-    assert_that!(fieldentry.is_set(), eq(false));
+    assert_that!(msg.optional_nested_message_opt().is_set(), eq(false));
 
-    fieldentry.or_default().set(submsg);
+    msg.set_optional_nested_message(submsg);
     // confirm that invoking .set on a submsg indeed flips the set bit
-    assert_that!(msg.optional_nested_message_mut().is_set(), eq(true));
+    assert_that!(msg.optional_nested_message_opt().is_set(), eq(true));
 
     msg.clear_optional_nested_message();
-    assert_that!(msg.optional_nested_message_mut().is_set(), eq(false));
+    assert_that!(msg.optional_nested_message_opt().is_set(), eq(false));
 }
 
 #[test]
 fn test_msg_or_default() {
     let mut msg = TestAllTypes::new();
-    assert_that!(msg.optional_nested_message_mut().is_set(), eq(false));
+    assert_that!(msg.optional_nested_message_opt().is_set(), eq(false));
 
     let _ = msg.optional_nested_message_mut().or_default();
     // confirm that that or_default makes the field Present
-    assert_that!(msg.optional_nested_message_mut().is_set(), eq(true));
+    assert_that!(msg.optional_nested_message_opt().is_set(), eq(true));
 
     msg.clear_optional_nested_message();
-    assert_that!(msg.optional_nested_message_mut().is_set(), eq(false));
+    assert_that!(msg.optional_nested_message_opt().is_set(), eq(false));
 }
 
 #[test]

src/google/protobuf/compiler/rust/accessors/singular_message.cc

@@ -73,7 +73,18 @@ void SingularMessage::InMsgImpl(Context& ctx, const FieldDescriptor& field,
                  return;
                }
                ctx.Emit({}, R"rs(
-                pub fn $raw_field_name$_mut(&mut self)
+                  pub fn $raw_field_name$_mut(&mut self) -> $msg_type$Mut<'_> {
+                    self.$raw_field_name$_entry().or_default()
+                  }
+                )rs");
+             }},
+            {"private_getter_entry",
+             [&] {
+               if (accessor_case == AccessorCase::VIEW) {
+                 return;
+               }
+               ctx.Emit({}, R"rs(
+                fn $raw_field_name$_entry(&mut self)
                     -> $pb$::FieldEntry<'_, $msg_type$> {
                   static VTABLE: $pbr$::MessageVTable =
                     $pbr$::MessageVTable::new($pbi$::Private,
@@ -109,7 +120,7 @@ void SingularMessage::InMsgImpl(Context& ctx, const FieldDescriptor& field,
                 pub fn set_$raw_field_name$(&mut self, val: impl $pb$::SettableValue<$msg_type$>) {
                   //~ TODO: Optimize this to not go through the
                   //~ FieldEntry.
-                  self.$raw_field_name$_mut().set(val);
+                  self.$raw_field_name$_entry().set(val);
                 }
               )rs");
              }},
@@ -124,6 +135,7 @@ void SingularMessage::InMsgImpl(Context& ctx, const FieldDescriptor& field,
            R"rs(
             $getter$
             $getter_mut$
+            $private_getter_entry$
             $getter_opt$
             $setter$
             $clearer$

src/google/protobuf/compiler/rust/message.cc

@@ -986,6 +986,9 @@ void GenerateRs(Context& ctx, const Descriptor& msg) {
             Self{ inner: $pbr$::MutatorMessageRef::new(_private, msg) }
           }
 
+          #[deprecated = "This .or_default() is a no-op, usages can be safely removed"]
+          pub fn or_default(self) -> Self { self }
+
           fn raw_msg(&self) -> $pbi$::RawMessage {
             self.inner.msg()
           }