[Clang] suppress -Wmissing-noreturn for virtual methods with throw-only bodies

Author: a-tarasyuk

clang/docs/ReleaseNotes.rst

@@ -417,6 +417,8 @@ Improvements to Clang's diagnostics
   or continue (#GH166013)
 - Clang now emits a diagnostic in case `vector_size` or `ext_vector_type`
   attributes are used with a negative size (#GH165463).
+- Clang no longer emits ``-Wmissing-noreturn`` for virtual methods where
+  the function body consists of a `throw` expression (#GH167247).
 
 Improvements to Clang's time-trace
 ----------------------------------

clang/lib/Sema/SemaDeclAttr.cpp

@@ -1966,8 +1966,9 @@ static bool isKnownToAlwaysThrow(const FunctionDecl *FD) {
   if (const auto *EWC = dyn_cast<ExprWithCleanups>(OnlyStmt)) {
     OnlyStmt = EWC->getSubExpr();
   }
-  // Check if the only statement is a throw expression.
-  return isa<CXXThrowExpr>(OnlyStmt);
+
+  const auto *MD = dyn_cast<CXXMethodDecl>(FD);
+  return isa<CXXThrowExpr>(OnlyStmt) && !(MD && MD->isVirtual());
 }
 
 void clang::inferNoReturnAttr(Sema &S, const Decl *D) {

clang/test/SemaCXX/wmissing-noreturn-suggestion.cpp

@@ -53,3 +53,12 @@ int gnu_throws() {
 int cxx11_throws() {
     throw 0;
 }
+
+namespace GH167247 {
+struct S {
+  virtual ~S() = default;
+  virtual void m() {
+    throw std::runtime_error("This method always throws");
+  }
+};
+}