Only clone Arc for source text

crates/oxc_sourcemap/src/concat_sourcemap_builder.rs

@@ -46,17 +46,20 @@ impl ConcatSourceMapBuilder {
         }
 
         // Extend `sources` and `source_contents`.
-        self.sources.extend(sourcemap.sources.iter().map(Arc::clone));
+        self.sources.extend(sourcemap.get_sources().map(Into::into));
 
         if let Some(source_contents) = &sourcemap.source_contents {
+            // Clone `Arc` instead of generating a new `Arc` and copying string data because
+            // source texts are generally long strings. Cost of copying a large string is higher
+            // than cloning an `Arc`.
             self.source_contents.extend(source_contents.iter().map(Arc::clone));
         } else {
             self.source_contents.extend((0..sourcemap.sources.len()).map(|_| Arc::default()));
         }
 
         // Extend `names`.
         self.names.reserve(sourcemap.names.len());
-        self.names.extend(sourcemap.names.iter().map(Arc::clone));
+        self.names.extend(sourcemap.get_names().map(Into::into));
 
         // Extend `tokens`.
         self.tokens.reserve(sourcemap.tokens.len());