Modules: Search for a visible definition of the decl context when computing visibility of a default template parameter

The code is/was already correct for the case where a parameter is a
parameter of its enclosing lexical DeclContext (functions and classes).
But for other templates (alias and variable templates) they don't create
their own scope to be members of - in those cases, they parameter should
be considered visible if any definition of the lexical decl context is
visible.

[this should cleanup the failure on the libstdc++ modules buildbot]
[this doesn't actually fix the variable template case for a
secondary/compounding reason (its lexical decl context is incorrectly
considered to be the translation unit)]

Test covers all 4 kinds of templates with default args, including a
regression test for the still broken variable template case.

Reviewers: rsmith

Differential Revision: https://reviews.llvm.org/D60892

llvm-svn: 358795
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias.h
new file mode 100644
index 0000000..cff3329
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias.h
@@ -0,0 +1,7 @@
+#ifndef ALIAS_H
+#define ALIAS_H
+struct alias_outer {
+  template <typename = int>
+  using alias = int;
+};
+#endif
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias1.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias1.h
new file mode 100644
index 0000000..736abcb
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias1.h
@@ -0,0 +1 @@
+#include "alias.h"
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias2.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias2.h
new file mode 100644
index 0000000..736abcb
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/alias2.h
@@ -0,0 +1 @@
+#include "alias.h"
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func.h
new file mode 100644
index 0000000..7a15c69
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func.h
@@ -0,0 +1,7 @@
+#ifndef FUNC_H
+#define FUNC_H
+struct func_outer {
+  template <typename = int>
+  void func();
+};
+#endif
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func1.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func1.h
new file mode 100644
index 0000000..940d767
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func1.h
@@ -0,0 +1 @@
+#include "func.h"
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func2.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func2.h
new file mode 100644
index 0000000..940d767
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/func2.h
@@ -0,0 +1 @@
+#include "func.h"
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/module.modulemap b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/module.modulemap
new file mode 100644
index 0000000..a0071fd
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/module.modulemap
@@ -0,0 +1,24 @@
+module ALIAS1 {
+  header "alias1.h"
+  module ALIAS2 {
+    header "alias2.h"
+  }
+}
+module VAR1 {
+  header "var1.h"
+  module VAR2 {
+    header "var2.h"
+  }
+}
+module FUNC1 {
+  header "func1.h"
+  module FUNC2 {
+    header "func2.h"
+  }
+}
+module STRCT1 {
+  header "strct1.h"
+  module STRCT2 {
+    header "strct2.h"
+  }
+}
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct.h
new file mode 100644
index 0000000..04d1244
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct.h
@@ -0,0 +1,7 @@
+#ifndef STRCT_H
+#define STRCT_H
+struct strct_outer {
+  template <typename = int>
+  struct strct;
+};
+#endif
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct1.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct1.h
new file mode 100644
index 0000000..5c29b94
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct1.h
@@ -0,0 +1 @@
+#include "strct.h"
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct2.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct2.h
new file mode 100644
index 0000000..5c29b94
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/strct2.h
@@ -0,0 +1 @@
+#include "strct.h"
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var.h
new file mode 100644
index 0000000..3c3584d
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var.h
@@ -0,0 +1,9 @@
+#ifndef VAR_H
+#define VAR_H
+struct var_outer {
+  template <typename = int>
+  static int var;
+};
+#endif
+
+
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var1.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var1.h
new file mode 100644
index 0000000..89cee81
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var1.h
@@ -0,0 +1 @@
+#include "var.h"
diff --git a/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var2.h b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var2.h
new file mode 100644
index 0000000..89cee81
--- /dev/null
+++ b/clang/test/Modules/Inputs/nested-template-default-arg-redecl/var2.h
@@ -0,0 +1 @@
+#include "var.h"
diff --git a/clang/test/Modules/nested-template-default-arg-redecl.cpp b/clang/test/Modules/nested-template-default-arg-redecl.cpp
new file mode 100644
index 0000000..3baa202
--- /dev/null
+++ b/clang/test/Modules/nested-template-default-arg-redecl.cpp
@@ -0,0 +1,18 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -x c++ -fmodules -fimplicit-module-maps -fmodules-cache-path=%t \
+// RUN:     -I %S/Inputs/nested-template-default-arg-redecl -std=c++14 \
+// RUN:     -fmodules-local-submodule-visibility -verify %s
+#include "alias2.h"
+#include "var2.h"
+#include "strct2.h"
+#include "func2.h"
+
+// FIXME: Variable templates lexical decl context appears to be the translation
+// unit, which is incorrect. Fixing this will hopefully address the following
+// error/bug:
+
+// expected-note@Inputs/nested-template-default-arg-redecl/var.h:4 {{default argument declared here}}
+auto var = &var_outer::var<>; // expected-error {{default argument of 'var' must be imported from module 'VAR1' before it is required}}
+auto func = &func_outer::func<>;
+strct_outer::strct<> *strct;
+alias_outer::alias<> *alias;