Add some comments about wha's kind of unused item will be warned

1 files changed, 7 insertions, 0 deletions

diff --git a/gcc/rust/lint/rust-lint-scan-deadcode.h b/gcc/rust/lint/rust-lint-scan-deadcode.h
index 1128818..6cf6281 100644
--- a/gcc/rust/lint/rust-lint-scan-deadcode.h
+++ b/gcc/rust/lint/rust-lint-scan-deadcode.h
@@ -29,6 +29,13 @@
 namespace Rust {
 namespace Analysis {
 
+// Scan item symbols and warn the symbol if it is not in the live_symbols set.
+// There are three kinds of item we should handle in this pass.
+// 1. Function item
+// 2. TODO: The function item in the impl block without trait
+// 3. StructStruct, e.g., `Struct Foo{one: 1, two: 2}`. Furthermore, the unused
+//    struct fields will be warned too.
+// 4. TupleStruct, e.g., `Struct Foo(i32, i32)`
 class ScanDeadcode : public MarkLiveBase
 {
   using Rust::Analysis::MarkLiveBase::visit;