From 0fc3a001682c0bd076a329024192e57b3bc950fd Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Wed, 3 Feb 2016 19:13:08 +0000
Subject: [PATCH] [Sema debugger support] Require non-void types to be complete
 in unknown-anytype casts.

When performing a cast from an __unknown_anytype function call to a
non-void type, we need to make sure that type is complete. Fixes
rdar://problem/23959960.

llvm-svn: 259681
---
 clang/lib/Sema/SemaExpr.cpp            |  6 ++++++
 clang/test/SemaCXX/unknown-anytype.cpp | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index b7d494fa..dc63879 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -14478,6 +14478,12 @@ ExprResult RebuildUnknownAnyExpr::resolveDecl(Expr *E, ValueDecl *VD) {
 ExprResult Sema::checkUnknownAnyCast(SourceRange TypeRange, QualType CastType,
                                      Expr *CastExpr, CastKind &CastKind,
                                      ExprValueKind &VK, CXXCastPath &Path) {
+  // The type we're casting to must be either void or complete.
+  if (!CastType->isVoidType() &&
+      RequireCompleteType(TypeRange.getBegin(), CastType,
+                          diag::err_typecheck_cast_to_incomplete))
+    return ExprError();
+
   // Rewrite the casted expression from scratch.
   ExprResult result = RebuildUnknownAnyExpr(*this, CastType).Visit(CastExpr);
   if (!result.isUsable()) return ExprError();
diff --git a/clang/test/SemaCXX/unknown-anytype.cpp b/clang/test/SemaCXX/unknown-anytype.cpp
index a07ec83..95ad040 100644
--- a/clang/test/SemaCXX/unknown-anytype.cpp
+++ b/clang/test/SemaCXX/unknown-anytype.cpp
@@ -45,3 +45,14 @@ namespace test4 {
     int x = (int) test1; // expected-error {{function 'test1' with unknown type must be given a function type}}
   }
 }
+
+// rdar://problem/23959960
+namespace test5 {
+  template<typename T> struct X; // expected-note{{template is declared here}}
+
+  extern __unknown_anytype test0(...);
+
+  void test() {
+    (X<int>)test0(); // expected-error{{implicit instantiation of undefined template 'test5::X<int>'}}
+  }
+}
-- 
2.7.4