[clang-tools-extra] [misc-coroutine-hostile-raii] Use getOperand instead of getCommonExpr. (PR #79206)

[Utkarsh Saxena via cfe-commits]

https://github.com/usx95 created https://github.com/llvm/llvm-project/pull/79206

We were previously allowlisting awaitable types returned by `await_transform` instead of the type of the operand of the `co_await` expression.

>From 28d90711ff8e4924135d4bd4e5f252d96ac41b93 Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Tue, 23 Jan 2024 20:18:25 +0000
Subject: [PATCH] [misc-coroutine-hostile-raii] Use getOperand instead of
 getCommonExpr

---
 .../misc/CoroutineHostileRAIICheck.cpp        |  2 +-
 .../checkers/misc/coroutine-hostile-raii.cpp  | 34 ++++++++++++++++++-
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/misc/CoroutineHostileRAIICheck.cpp b/clang-tools-extra/clang-tidy/misc/CoroutineHostileRAIICheck.cpp
index a0e8700b0522bc5..360335b86c6418e 100644
--- a/clang-tools-extra/clang-tidy/misc/CoroutineHostileRAIICheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/CoroutineHostileRAIICheck.cpp
@@ -56,7 +56,7 @@ AST_MATCHER_P(Stmt, forEachPrevStmt, ast_matchers::internal::Matcher<Stmt>,
 // Matches the expression awaited by the `co_await`.
 AST_MATCHER_P(CoawaitExpr, awaitable, ast_matchers::internal::Matcher<Expr>,
               InnerMatcher) {
-  if (Expr *E = Node.getCommonExpr())
+  if (Expr *E = Node.getOperand())
     return InnerMatcher.matches(*E, Finder, Builder);
   return false;
 }
diff --git a/clang-tools-extra/test/clang-tidy/checkers/misc/coroutine-hostile-raii.cpp b/clang-tools-extra/test/clang-tidy/checkers/misc/coroutine-hostile-raii.cpp
index 55a7e4b8f2954aa..c23c355dac1b2ae 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/misc/coroutine-hostile-raii.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/misc/coroutine-hostile-raii.cpp
@@ -1,7 +1,7 @@
 // RUN: %check_clang_tidy -std=c++20 %s misc-coroutine-hostile-raii %t \
 // RUN:   -config="{CheckOptions: {\
 // RUN:             misc-coroutine-hostile-raii.RAIITypesList: 'my::Mutex; ::my::other::Mutex', \
-// RUN:             misc-coroutine-hostile-raii.AllowedAwaitablesList: 'safe::awaitable; ::my::other::awaitable' \
+// RUN:             misc-coroutine-hostile-raii.AllowedAwaitablesList: 'safe::awaitable; ::transformable::awaitable' \
 // RUN:             }}"
 
 namespace std {
@@ -136,6 +136,9 @@ ReturnObject scopedLockableTest() {
     absl::Mutex no_warning_5;
 }
 
+// ================================================================================
+// Safe awaitable
+// ================================================================================
 namespace safe {
   struct awaitable {
   bool await_ready() noexcept { return false; }
@@ -150,6 +153,32 @@ ReturnObject RAIISafeSuspendTest() {
   co_await other{};
 } 
 
+// ================================================================================
+// Safe transformable awaitable
+// ================================================================================
+struct transformable { struct awaitable{}; };
+using alias_transformable_awaitable = transformable::awaitable;
+struct UseTransformAwaitable {
+  struct promise_type {
+    UseTransformAwaitable get_return_object() { return {}; }
+    std::suspend_always initial_suspend() { return {}; }
+    std::suspend_always final_suspend() noexcept { return {}; }
+    void unhandled_exception() {}
+    std::suspend_always await_transform(transformable::awaitable) { return {}; }
+  };
+};
+
+auto retAwaitable() { return transformable::awaitable{}; }
+UseTransformAwaitable RAIISafeSuspendTest2() {
+  absl::Mutex a;
+  co_await retAwaitable();
+  co_await transformable::awaitable{};
+  co_await alias_transformable_awaitable{};
+}
+
+// ================================================================================
+// Lambdas
+// ================================================================================
 void lambda() {
   absl::Mutex no_warning;
   auto lambda = []() -> ReturnObject {
@@ -164,6 +193,9 @@ void lambda() {
   absl::Mutex no_warning_2;
 }
 
+// ================================================================================
+// Denylisted RAII
+// ================================================================================
 template<class T>
 ReturnObject raii_in_template(){
   T a;