[modules] Ensure we've imported all declarations of a template before
attempting to lazily deserialize its specializations; otherwise, there might be
pending specializations that we don't know about yet.
llvm-svn: 230301
diff --git a/clang/test/Modules/redecl-templates.cpp b/clang/test/Modules/redecl-templates.cpp
new file mode 100644
index 0000000..6bbec02
--- /dev/null
+++ b/clang/test/Modules/redecl-templates.cpp
@@ -0,0 +1,32 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -x c++ -I %S/Inputs/redecl-templates %s -verify -std=c++14
+// RUN: %clang_cc1 -x c++ -fmodules -fmodules-cache-path=%t -I %S/Inputs/redecl-templates %s -verify -std=c++14
+// expected-no-diagnostics
+
+template<int N> struct A {};
+template<int N> using X = A<N>;
+
+template<int N> constexpr void f() {}
+template<int N> constexpr void g() { f<N>(); }
+
+template<int N> extern int v;
+template<int N> int &w = v<N>;
+
+#include "a.h"
+
+// Be careful not to mention A here, that'll import the decls from "a.h".
+int g(X<1> *);
+X<1> *p = 0;
+
+// This will implicitly instantiate A<1> if we haven't imported the explicit
+// specialization declaration from "a.h".
+int k = g(p);
+// Likewise for f and v.
+void h() { g<1>(); }
+int &x = w<1>;
+
+// This is OK: we declared the explicit specialization before we triggered
+// instantiation of this specialization.
+template<> struct A<1> {};
+template<> constexpr void f<1>() {}
+template<> int v<1>;