Fix some non-breaking issues with rust gencode.

- Stop emitting a clear thunk for without-presence string/bytes fields (was unused, but would link-error it was used since there's no such operation).
- Remove unused clearer_thunk variable in message.cc
- Remove unsafe{} block surrounding non-unsafe BytesMutVTable::new
- Add #[allow(non_snake_case)] on module names (the new mangling added in cr/593048297 puts double-underscore in names which rustc recognizes as non-snake).

PiperOrigin-RevId: 594236747

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

@@ -122,7 +122,7 @@ void SingularScalar::InExternC(Context& ctx,
             {"getter_thunk", Thunk(ctx, field, "get")},
             {"setter_thunk", Thunk(ctx, field, "set")},
             {"clearer_thunk", Thunk(ctx, field, "clear")},
-            {"hazzer_and_clearer",
+            {"thunks_for_with_presence_fields",
              [&] {
                if (field.has_presence()) {
                  ctx.Emit(
@@ -133,7 +133,7 @@ void SingularScalar::InExternC(Context& ctx,
                }
              }}},
            R"rs(
-          $hazzer_and_clearer$
+          $thunks_for_with_presence_fields$
           fn $getter_thunk$(raw_msg: $pbi$::RawMessage) -> $Scalar$;
           fn $setter_thunk$(raw_msg: $pbi$::RawMessage, val: $Scalar$);
         )rs");
@@ -148,7 +148,7 @@ void SingularScalar::InThunkCc(Context& ctx,
             {"getter_thunk", Thunk(ctx, field, "get")},
             {"setter_thunk", Thunk(ctx, field, "set")},
             {"clearer_thunk", Thunk(ctx, field, "clear")},
-            {"hazzer_and_clearer",
+            {"thunks_for_with_presence_fields",
              [&] {
                if (field.has_presence()) {
                  ctx.Emit(R"cc(
@@ -160,7 +160,7 @@ void SingularScalar::InThunkCc(Context& ctx,
                }
              }}},
            R"cc(
-             $hazzer_and_clearer$;
+             $thunks_for_with_presence_fields$;
              $Scalar$ $getter_thunk$($QualifiedMsg$* msg) { return msg->$field$(); }
              void $setter_thunk$($QualifiedMsg$* msg, $Scalar$ val) {
                msg->set_$field$(val);

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

@@ -118,13 +118,12 @@ void SingularString::InMsgImpl(Context& ctx,
                          {"setter_thunk", setter_thunk}},
                         R"rs(
               pub fn $field$_mut(&mut self) -> $pb$::Mut<'_, $proxied_type$> {
-                static VTABLE: $pbi$::BytesMutVTable = unsafe {
+                static VTABLE: $pbi$::BytesMutVTable =
                   $pbi$::BytesMutVTable::new(
                     $pbi$::Private,
                     $getter_thunk$,
                     $setter_thunk$,
-                  )
-                };
+                  );
                 unsafe {
                   <$pb$::Mut<$proxied_type$>>::from_inner(
                     $pbi$::Private,
@@ -158,19 +157,19 @@ void SingularString::InExternC(Context& ctx,
             {"getter_thunk", Thunk(ctx, field, "get")},
             {"setter_thunk", Thunk(ctx, field, "set")},
             {"clearer_thunk", Thunk(ctx, field, "clear")},
-            {"hazzer",
+            {"thunks_for_with_presence_fields",
              [&] {
                if (field.has_presence()) {
                  ctx.Emit(R"rs(
                      fn $hazzer_thunk$(raw_msg: $pbi$::RawMessage) -> bool;
+                     fn $clearer_thunk$(raw_msg: $pbi$::RawMessage);
                    )rs");
                }
              }}},
            R"rs(
-          $hazzer$
+          $thunks_for_with_presence_fields$
           fn $getter_thunk$(raw_msg: $pbi$::RawMessage) -> $pbi$::PtrAndLen;
           fn $setter_thunk$(raw_msg: $pbi$::RawMessage, val: $pbi$::PtrAndLen);
-          fn $clearer_thunk$(raw_msg: $pbi$::RawMessage);
         )rs");
 }
 
@@ -182,7 +181,7 @@ void SingularString::InThunkCc(Context& ctx,
             {"getter_thunk", Thunk(ctx, field, "get")},
             {"setter_thunk", Thunk(ctx, field, "set")},
             {"clearer_thunk", Thunk(ctx, field, "clear")},
-            {"hazzer",
+            {"thunks_for_with_presence_fields",
              [&] {
                if (field.has_presence()) {
                  ctx.Emit(R"cc(
@@ -194,7 +193,7 @@ void SingularString::InThunkCc(Context& ctx,
                }
              }}},
            R"cc(
-             $hazzer$;
+             $thunks_for_with_presence_fields$;
              ::google::protobuf::rust_internal::PtrAndLen $getter_thunk$($QualifiedMsg$* msg) {
                absl::string_view val = msg->$field$();
                return ::google::protobuf::rust_internal::PtrAndLen(val.data(), val.size());

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

@@ -54,6 +54,7 @@ void EmitOpeningOfPackageModules(Context& ctx, absl::string_view pkg) {
   for (absl::string_view segment : absl::StrSplit(pkg, '.')) {
     ctx.Emit({{"segment", segment}},
              R"rs(
+           #[allow(non_snake_case)]
            pub mod $segment$ {
            )rs");
   }
@@ -157,6 +158,7 @@ void DeclareSubmodulesForNonPrimarySrcs(
               {"mod_name", RustInternalModuleName(ctx, *non_primary_src)}},
              R"rs(
                         #[path="$file_path$"]
+                        #[allow(non_snake_case)]
                         pub mod $mod_name$;
                       )rs");
   }

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

@@ -175,7 +175,6 @@ void GetterForViewOrMut(Context& ctx, const FieldDescriptor& field,
   auto fieldType = field.type();
   auto getter_thunk = Thunk(ctx, field, "get");
   auto setter_thunk = Thunk(ctx, field, "set");
-  auto clearer_thunk = Thunk(ctx, field, "clear");
   // If we're dealing with a Mut, the getter must be supplied
   // self.inner.msg() whereas a View has to be supplied self.msg
   auto self = is_mut ? "self.inner.msg()" : "self.msg";
@@ -240,7 +239,6 @@ void GetterForViewOrMut(Context& ctx, const FieldDescriptor& field,
   ctx.Emit({{"field", fieldName},
             {"getter_thunk", getter_thunk},
             {"setter_thunk", setter_thunk},
-            {"clearer_thunk", clearer_thunk},
             {"self", self},
             {"RsType", rsType},
             {"as_ref", asRef},