From f332498f9880d276890562fb861a375a13bfd9d9 Mon Sep 17 00:00:00 2001
From: Deniz Evrenci <denizevrenci@gmail.com>
Date: Tue, 28 Feb 2023 11:36:46 +0100
Subject: [PATCH] [Clang] Do not emit exception diagnostics from coroutines and
 coroutine lambdas

All exceptions thrown in coroutine bodies are caught and
unhandled_exception member of the coroutine promise type is called.
In accordance with the existing rules of diagnostics related to
exceptions thrown in functions marked noexcept, even if the promise
type's constructor, get_return_object, or unhandled_exception
throws, diagnostics should not be emitted.

Fixes #48797.

Differential Revision: https://reviews.llvm.org/D144352
---
 clang/lib/Sema/AnalysisBasedWarnings.cpp           |  2 +-
 .../test/SemaCXX/warn-throw-out-noexcept-coro.cpp  | 63 ++++++++++++++++++++++
 2 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/SemaCXX/warn-throw-out-noexcept-coro.cpp

diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 07e17f9..4367435 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -2509,7 +2509,7 @@ void clang::sema::AnalysisBasedWarnings::IssueWarnings(
   // Check for throw out of non-throwing function.
   if (!Diags.isIgnored(diag::warn_throw_in_noexcept_func, D->getBeginLoc()))
     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
-      if (S.getLangOpts().CPlusPlus && isNoexcept(FD))
+      if (S.getLangOpts().CPlusPlus && !fscope->isCoroutine() && isNoexcept(FD))
         checkThrowInNonThrowingFunc(S, FD, AC);
 
   // Emit unsafe buffer usage warnings and fixits.
diff --git a/clang/test/SemaCXX/warn-throw-out-noexcept-coro.cpp b/clang/test/SemaCXX/warn-throw-out-noexcept-coro.cpp
new file mode 100644
index 0000000..4d52bdc
--- /dev/null
+++ b/clang/test/SemaCXX/warn-throw-out-noexcept-coro.cpp
@@ -0,0 +1,63 @@
+// RUN: %clang_cc1 -std=c++20 %s -fcxx-exceptions -fsyntax-only -Wexceptions -verify -fdeclspec
+
+#include "Inputs/std-coroutine.h"
+
+// expected-no-diagnostics
+
+template <typename T>
+struct promise;
+
+template <typename T>
+struct task {
+    using promise_type = promise<T>;
+
+    explicit task(promise_type& p) { throw 1; p.return_val = this; }
+
+    task(const task&) = delete;
+
+    T value;
+};
+
+template <typename T>
+struct promise {
+    task<T> get_return_object() { return task{*this}; }
+
+    std::suspend_never initial_suspend() const noexcept { return {}; }
+
+    std::suspend_never final_suspend() const noexcept { return {}; }
+
+    template <typename U>
+    void return_value(U&& val) { return_val->value = static_cast<U&&>(val); }
+
+    void unhandled_exception() { throw 1; }
+
+    task<T>* return_val;
+};
+
+task<int> a_ShouldNotDiag(const int a, const int b) {
+  if (b == 0)
+    throw b;
+
+  co_return a / b;
+}
+
+task<int> b_ShouldNotDiag(const int a, const int b) noexcept {
+  if (b == 0)
+    throw b;
+
+  co_return a / b;
+}
+
+const auto c_ShouldNotDiag = [](const int a, const int b) -> task<int> {
+  if (b == 0)
+    throw b;
+
+  co_return a / b;
+};
+
+const auto d_ShouldNotDiag = [](const int a, const int b) noexcept -> task<int> {
+  if (b == 0)
+    throw b;
+
+  co_return a / b;
+};
-- 
2.7.4