[clang] Warn const integer-overflow of member in temporary struct bound to rvalue reference

Fixes #46755

Author: JOE1994

clang/docs/ReleaseNotes.rst

@@ -578,6 +578,9 @@ Improvements to Clang's diagnostics
 
 - Clang now omits shadowing warnings for parameter names in explicit object member functions (#GH95707).
 
+- For an rvalue reference bound to a temporary struct with an integer member, Clang will detect constant integer overflow
+  in the initializer for the integer member (#GH46755).
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/lib/Sema/SemaChecking.cpp

@@ -12048,7 +12048,8 @@ void Sema::CheckForIntOverflow (const Expr *E) {
              New && New->isArray()) {
       if (auto ArraySize = New->getArraySize())
         Exprs.push_back(*ArraySize);
-    }
+    } else if (const auto *Mte = dyn_cast<MaterializeTemporaryExpr>(OriginalE))
+      Exprs.push_back(Mte->getSubExpr());
   } while (!Exprs.empty());
 }
 

clang/test/SemaCXX/integer-overflow.cpp

@@ -246,4 +246,10 @@ int m() {
     return 0;
 }
 }
+
+namespace GH46755 {
+void f() {
+    struct { int v; } &&r = {512 * 1024 * 1024 * 1024}; // expected-warning {{overflow in expression; result is 0 with type 'int'}}
+}
+}
 #endif