build: fix some compiler warnings

lib/message/mu-contact.hh

@@ -129,6 +129,8 @@ struct Contact {
 	 * @return the field-id or Nothing.
 	 */
 	constexpr Option<Field::Id> field_id() const noexcept {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wswitch-enum"
 		switch(type) {
 		case Type::Bcc:
 			return Field::Id::Bcc;
@@ -141,6 +143,7 @@ struct Contact {
 		default:
 			return Nothing;
 		}
+#pragma GCC diagnostic pop
 	}
 
 
@@ -167,6 +170,8 @@ private:
 constexpr Option<Contact::Type>
 contact_type_from_field_id(Field::Id id) noexcept {
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wswitch-enum"
 	switch(id) {
 	case Field::Id::Bcc:
 		return Contact::Type::Bcc;
@@ -179,6 +184,7 @@ contact_type_from_field_id(Field::Id id) noexcept {
 	default:
 		return Nothing;
 	}
+#pragma GCC diagnostic pop
 }
 
 using Contacts = std::vector<Contact>;

lib/message/mu-message.cc

@@ -490,6 +490,9 @@ handle_object(const MimeObject& parent,
 		info.flags |= Flags::Encrypted;
 	} else if (obj.is_mime_application_pkcs7_mime()) {
 		MimeApplicationPkcs7Mime smime(obj);
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wswitch-enum"
+		// CompressedData, CertsOnly, Unknown
 		switch (smime.smime_type()) {
 		case Mu::MimeApplicationPkcs7Mime::SecureMimeType::SignedData:
 			info.flags |= Flags::Signed;
@@ -500,6 +503,7 @@ handle_object(const MimeObject& parent,
 		default:
 			break;
 		}
+#pragma GCC diagnostic pop
 	}
 }
 
@@ -718,6 +722,7 @@ fill_document(Message::Private& priv)
 			break;
 		/* LCOV_EXCL_START */
 		case Field::Id::_count_:
+		default:
 			break;
 		/* LCOV_EXCL_STOP */
 		}

lib/message/mu-mime-object.cc

@@ -331,6 +331,7 @@ address_type(Contact::Type ctype)
 		return GMIME_ADDRESS_TYPE_REPLY_TO;
 	case Contact::Type::Sender:
 		return GMIME_ADDRESS_TYPE_SENDER;
+	case Contact::Type::None:
 	default:
 		return Nothing;
 	}