do not re-export and refine docs

Signed-off-by: Bugen Zhao <i@bugenzhao.com>

src/frontend/src/binder/bind_param.rs

@@ -15,11 +15,12 @@
 use bytes::Bytes;
 use pgwire::types::{Format, FormatIterator};
 use risingwave_common::bail;
+use risingwave_common::error::BoxedError;
 use risingwave_common::types::{Datum, ScalarImpl};
 
 use super::statement::RewriteExprsRecursive;
 use super::BoundStatement;
-use crate::error::{BoxedError, ErrorCode, Result};
+use crate::error::{ErrorCode, Result};
 use crate::expr::{Expr, ExprImpl, ExprRewriter, Literal};
 
 /// Rewrites parameter expressions to literals.

src/frontend/src/catalog/system_catalog/mod.rs

@@ -26,6 +26,7 @@ use risingwave_common::catalog::{
     ColumnCatalog, ColumnDesc, Field, SysCatalogReader, TableDesc, TableId, DEFAULT_SUPER_USER_ID,
     NON_RESERVED_SYS_CATALOG_ID,
 };
+use risingwave_common::error::BoxedError;
 use risingwave_common::row::OwnedRow;
 use risingwave_common::types::DataType;
 use risingwave_pb::meta::list_table_fragment_states_response::TableFragmentState;
@@ -37,7 +38,6 @@ use crate::catalog::system_catalog::information_schema::*;
 use crate::catalog::system_catalog::pg_catalog::*;
 use crate::catalog::system_catalog::rw_catalog::*;
 use crate::catalog::view_catalog::ViewCatalog;
-use crate::error::BoxedError;
 use crate::meta_client::FrontendMetaClient;
 use crate::scheduler::worker_node_manager::WorkerNodeManagerRef;
 use crate::session::AuthContext;

src/frontend/src/error.rs

@@ -1,6 +1,20 @@
+// Copyright 2024 RisingWave Labs
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 use risingwave_batch::error::BatchError;
 use risingwave_common::array::ArrayError;
-pub use risingwave_common::error::*;
+use risingwave_common::error::{BoxedError, NoFunction, NotImplemented};
 use risingwave_common::session_config::SessionConfigError;
 use risingwave_common::util::value_encoding::error::ValueEncodingError;
 use risingwave_connector::sink::SinkError;
@@ -10,6 +24,13 @@ use risingwave_rpc_client::error::{RpcError, TonicStatusWrapper};
 use thiserror::Error;
 use thiserror_ext::Box;
 
+/// The error type for the frontend crate, acting as the top-level error type for the
+/// entire RisingWave project.
+// TODO(error-handling): this is migrated from the `common` crate, and there could
+// be some further refactoring to do:
+// - Some variants are never constructed.
+// - Some variants store a type-erased `BoxedError` to resolve the reverse dependency.
+//   It's not necessary anymore as the error type is now defined at the top-level.
 #[derive(Error, Debug, Box)]
 #[thiserror_ext(newtype(name = RwError, backtrace, report_debug))]
 pub enum ErrorCode {
@@ -144,6 +165,7 @@ pub enum ErrorCode {
     ),
 }
 
+/// The result type for the frontend crate.
 pub type Result<T> = std::result::Result<T, RwError>;
 
 impl From<TonicStatusWrapper> for RwError {