7 files changed, 131 insertions, 6 deletions
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 04a39c07aaf..94eead8641f 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -5708,8 +5708,6 @@ void ASTWriter::CompletedTagDefinition(const TagDecl *D) {
 }
 
 void ASTWriter::AddedVisibleDecl(const DeclContext *DC, const Decl *D) {
-  assert(!WritingAST && "Already writing the AST!");
-
   // TU and namespaces are handled elsewhere.
   if (isa<TranslationUnitDecl>(DC) || isa<NamespaceDecl>(DC))
     return;
@@ -5718,12 +5716,12 @@ void ASTWriter::AddedVisibleDecl(const DeclContext *DC, const Decl *D) {
     return; // Not a source decl added to a DeclContext from PCH.
 
   assert(!getDefinitiveDeclContext(DC) && "DeclContext not definitive!");
+  assert(!WritingAST && "Already writing the AST!");
   AddUpdatedDeclContext(DC);
   UpdatingVisibleDecls.push_back(D);
 }
 
 void ASTWriter::AddedCXXImplicitMember(const CXXRecordDecl *RD, const Decl *D) {
-  assert(!WritingAST && "Already writing the AST!");
   assert(D->isImplicit());
   if (!(!D->isFromASTFile() && RD->isFromASTFile()))
     return; // Not a source member added to a class from PCH.
@@ -5732,17 +5730,18 @@ void ASTWriter::AddedCXXImplicitMember(const CXXRecordDecl *RD, const Decl *D) {
 
   // A decl coming from PCH was modified.
   assert(RD->isCompleteDefinition());
+  assert(!WritingAST && "Already writing the AST!");
   DeclUpdates[RD].push_back(DeclUpdate(UPD_CXX_ADDED_IMPLICIT_MEMBER, D));
 }
 
 void ASTWriter::AddedCXXTemplateSpecialization(const ClassTemplateDecl *TD,
                                      const ClassTemplateSpecializationDecl *D) {
   // The specializations set is kept in the canonical template.
-  assert(!WritingAST && "Already writing the AST!");
   TD = TD->getCanonicalDecl();
   if (!(!D->isFromASTFile() && TD->isFromASTFile()))
     return; // Not a source specialization added to a template from PCH.
 
+  assert(!WritingAST && "Already writing the AST!");
   DeclUpdates[TD].push_back(DeclUpdate(UPD_CXX_ADDED_TEMPLATE_SPECIALIZATION,
                                        D));
 }
@@ -5750,11 +5749,11 @@ void ASTWriter::AddedCXXTemplateSpecialization(const ClassTemplateDecl *TD,
 void ASTWriter::AddedCXXTemplateSpecialization(
     const VarTemplateDecl *TD, const VarTemplateSpecializationDecl *D) {
   // The specializations set is kept in the canonical template.
-  assert(!WritingAST && "Already writing the AST!");
   TD = TD->getCanonicalDecl();
   if (!(!D->isFromASTFile() && TD->isFromASTFile()))
     return; // Not a source specialization added to a template from PCH.
 
+  assert(!WritingAST && "Already writing the AST!");
   DeclUpdates[TD].push_back(DeclUpdate(UPD_CXX_ADDED_TEMPLATE_SPECIALIZATION,
                                        D));
 }
@@ -5762,11 +5761,11 @@ void ASTWriter::AddedCXXTemplateSpecialization(
 void ASTWriter::AddedCXXTemplateSpecialization(const FunctionTemplateDecl *TD,
                                                const FunctionDecl *D) {
   // The specializations set is kept in the canonical template.
-  assert(!WritingAST && "Already writing the AST!");
   TD = TD->getCanonicalDecl();
   if (!(!D->isFromASTFile() && TD->isFromASTFile()))
     return; // Not a source specialization added to a template from PCH.
 
+  assert(!WritingAST && "Already writing the AST!");
   DeclUpdates[TD].push_back(DeclUpdate(UPD_CXX_ADDED_TEMPLATE_SPECIALIZATION,
                                        D));
 }
diff --git a/clang/test/Modules/Inputs/PR20399/FirstHeader.h b/clang/test/Modules/Inputs/PR20399/FirstHeader.h
new file mode 100644
index 00000000000..c8005227b35
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR20399/FirstHeader.h
@@ -0,0 +1,17 @@
+#ifndef FIRSTHEADER
+#define FIRSTHEADER
+
+#include "SecondHeader.h" // Just a class which gets in the lazy deserialization chain
+
+#include "stl_map.h"
+#include "vector"
+struct A {
+   typedef std::map<int, int*>::iterator el;
+};
+
+struct B {
+  ~B() {}
+  std::vector<int> fvec; // Cannot replace with simple mockup
+};
+
+#endif
diff --git a/clang/test/Modules/Inputs/PR20399/SecondHeader.h b/clang/test/Modules/Inputs/PR20399/SecondHeader.h
new file mode 100644
index 00000000000..8548cc563ab
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR20399/SecondHeader.h
@@ -0,0 +1,13 @@
+#ifndef SECONDHEADER
+#define SECONDHEADER
+
+#include "vector"
+
+class Collection {
+  template <class T> struct Address { };
+};
+
+template <> struct Collection::Address<std::vector<bool> >
+   : public Collection::Address<std::vector<bool>::iterator> { };
+
+#endif
diff --git a/clang/test/Modules/Inputs/PR20399/module.modulemap b/clang/test/Modules/Inputs/PR20399/module.modulemap
new file mode 100644
index 00000000000..223434adba1
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR20399/module.modulemap
@@ -0,0 +1,18 @@
+module stdlib [system] {
+    header "stl_map.h"
+    header "vector"
+ }
+
+module libCore {
+  header "SecondHeader.h"
+    use stdlib
+  export *
+}
+
+module libGdml {
+  header "FirstHeader.h"
+  use libCore
+    use stdlib
+  export *
+}
+
diff --git a/clang/test/Modules/Inputs/PR20399/stl_map.h b/clang/test/Modules/Inputs/PR20399/stl_map.h
new file mode 100644
index 00000000000..11da0425348
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR20399/stl_map.h
@@ -0,0 +1,25 @@
+namespace std
+{
+  template<typename _Iterator>
+  class reverse_iterator {};
+
+  template<typename _Iterator>
+  inline int*
+  operator-(const int& __x, const reverse_iterator<_Iterator>& __y) {};
+
+  template<typename _Tp>
+  struct _Rb_tree_iterator
+  {
+    typedef _Rb_tree_iterator<_Tp>        _Self;
+  };
+
+  template <typename _Key, typename _Tp >
+  class map
+  {
+  public:
+    typedef _Rb_tree_iterator<int>        iterator;
+
+    template<typename _K1, typename _T1>
+    friend bool operator<(const map<_K1, _T1>&, const map<_K1, _T1>&);
+  };
+} // namespace std
diff --git a/clang/test/Modules/Inputs/PR20399/vector b/clang/test/Modules/Inputs/PR20399/vector
new file mode 100644
index 00000000000..379e4661d35
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR20399/vector
@@ -0,0 +1,51 @@
+namespace std
+{
+  template<typename _Tp, typename _Alloc = int>
+  class vector
+  {
+  public:
+    int* _M_start;
+    int* _M_end_of_storage;
+
+    ~vector()
+    { this->_M_end_of_storage - this->_M_start; }
+  };
+
+  struct _Bit_iterator {};
+
+  inline int* operator-(const _Bit_iterator& __x, const _Bit_iterator& __y)
+  {
+    return 0;
+  }
+
+  struct _Bvector_base
+  {
+    struct _Bvector_impl
+    {
+      _Bit_iterator     _M_start;
+
+      _Bvector_impl() { }
+    };
+
+    public:
+    ~_Bvector_base()
+    { this->_M_deallocate(); }
+
+  protected:
+    _Bvector_impl _M_impl;
+
+    void _M_deallocate() {}
+  };
+
+  template<typename _Alloc>
+  class vector<bool, _Alloc> : protected _Bvector_base
+  {
+    typedef _Bvector_base                      _Base;
+  public:
+    typedef _Bit_iterator          iterator;
+
+    vector()
+      : _Base() { }
+  };
+
+} // namespace std
diff --git a/clang/test/Modules/pr20399.cpp b/clang/test/Modules/pr20399.cpp
new file mode 100644
index 00000000000..4f4a02561fc
--- /dev/null
+++ b/clang/test/Modules/pr20399.cpp
@@ -0,0 +1,2 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fmodule-name=libGdml -emit-module -x c++ -std=c++11 %S/Inputs/PR20399/module.modulemap