chore: Improve docs (#2301)

Cargo.lock

@@ -2429,7 +2429,7 @@ dependencies = [
 
 [[package]]
 name = "swc_common"
-version = "0.12.1"
+version = "0.12.2"
 dependencies = [
  "ahash",
  "arbitrary",

common/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2018"
 license = "Apache-2.0/MIT"
 name = "swc_common"
 repository = "https://github.com/swc-project/swc.git"
-version = "0.12.1"
+version = "0.12.2"
 
 [features]
 concurrent = ["parking_lot"]

common/src/source_map.rs

@@ -110,6 +110,18 @@ pub(super) struct SourceMapFiles {
 ///  - Each ast node only stores pointer to actual data ([BytePos]).
 ///  - The pointers ([BytePos]) can be converted to file name, line and column
 ///    using this struct.
+///
+/// # Note
+///
+/// This struct should be shared. `swc_common` uses [crate::sync::Lrc], which is
+/// [std::rc::Rc] or [std::sync::Arc], depending on the compile option, for this
+/// purpose.
+///
+/// ## Note for bundler authors
+///
+/// If you are bundling modules, you should share this struct while parsing
+/// modules. Otherwise, you have to implement a code generator which accepts
+/// multiple [SourceMap].
 pub struct SourceMap {
     pub(super) files: Lock<SourceMapFiles>,
     start_pos: AtomicUsize,