It's an error to use a function declared in a class definition as a default argument before the function has been declared.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@73234 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 1abd5fb..c01c812 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -2484,9 +2484,19 @@
       // Pass the argument.
       if (PerformCopyInitialization(Arg, ProtoArgType, "passing"))
         return true;
-    } else
+    } else {
+      if (FDecl->getParamDecl(i)->hasUnparsedDefaultArg()) {
+        Diag (Call->getSourceRange().getBegin(),
+              diag::err_use_of_default_argument_to_function_declared_later) <<
+        FDecl << cast<CXXRecordDecl>(FDecl->getDeclContext())->getDeclName();
+        Diag(UnparsedDefaultArgLocs[FDecl->getParamDecl(i)], 
+              diag::note_default_argument_declared_here);
+      }
+      
       // We already type-checked the argument, so we know it works.
       Arg = new (Context) CXXDefaultArgExpr(FDecl->getParamDecl(i));
+    }
+    
     QualType ArgType = Arg->getType();
 
     Call->setArg(i, Arg);