Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -15409,7 +15409,10 @@
 
 ExprResult Sema::CheckBooleanCondition(SourceLocation Loc, Expr *E,
                                        bool IsConstexpr) {
-  DiagnoseAssignmentAsCondition(E);
+  // an assignment always produces an lvalue, and we now check this inside
+  // PerformImplicitConversion, as conditions will always be implicitly
+  // converted to an rvalue
+  // DiagnoseAssignmentAsCondition(E);
   if (ParenExpr *parenE = dyn_cast<ParenExpr>(E))
     DiagnoseEqualityWithExtraParens(parenE);
 
Index: lib/Sema/SemaExprCXX.cpp
===================================================================
--- lib/Sema/SemaExprCXX.cpp
+++ lib/Sema/SemaExprCXX.cpp
@@ -3860,6 +3860,10 @@
 
   case ICK_Lvalue_To_Rvalue: {
     assert(From->getObjectKind() != OK_ObjCProperty);
+    if (SCS.Second == ICK_Boolean_Conversion ||
+        From->getType() == Context.BoolTy) {
+      DiagnoseAssignmentAsCondition(From->IgnoreImpCasts());
+    }
     ExprResult FromRes = DefaultLvalueConversion(From);
     assert(!FromRes.isInvalid() && "Can't perform deduced conversion?!");
     From = FromRes.get();