Switch the semantic DeclContext for a block-scope declaration of a function or

variable from being the function to being the enclosing namespace scope (in
C++) or the TU (in C). This allows us to fix a selection of related issues
where we would build incorrect redeclaration chains for such declarations, and
fail to notice type mismatches.

Such declarations are put into a new IdentifierNamespace, IDNS_LocalExtern,
which is only found when searching scopes, and not found when searching
DeclContexts. Such a declaration is only made visible in its DeclContext if
there are no non-LocalExtern declarations.

llvm-svn: 191064

1 files changed, 73 insertions, 0 deletions

diff --git a/clang/test/CXX/basic/basic.link/p7.cpp b/clang/test/CXX/basic/basic.link/p7.cpp
new file mode 100644
index 00000000000..9a85eacdda4
--- /dev/null
+++ b/clang/test/CXX/basic/basic.link/p7.cpp
@@ -0,0 +1,73 @@
+// RUN: %clang_cc1 -verify -std=c++1y %s
+
+// Example from the standard.
+namespace X {
+  void p() {
+    q(); // expected-error {{undeclared}}
+    extern void q();
+  }
+  void middle() {
+    q(); // expected-error {{undeclared}}
+  }
+  void q() { /*...*/ }
+  void bottom() {
+    q();
+  }
+}
+int q();
+
+namespace Test1 {
+  void f() {
+    extern int a; // expected-note {{previous}}
+    int g(void); // expected-note {{previous}}
+  }
+  double a; // expected-error {{different type: 'double' vs 'int'}}
+  double g(); // expected-error {{differ only in their return type}}
+}
+
+namespace Test2 {
+  void f() {
+    extern int a; // expected-note {{previous}}
+    int g(void); // expected-note {{previous}}
+  }
+  void h() {
+    extern double a; // expected-error {{different type: 'double' vs 'int'}}
+    double g(void); // expected-error {{differ only in their return type}}
+  }
+}
+
+namespace Test3 {
+  constexpr void (*f())() {
+    void h();
+    return &h;
+  }
+  constexpr void (*g())() {
+    void h();
+    return &h;
+  }
+  static_assert(f() == g(), "");
+}
+
+namespace Test4 {
+  template<typename T>
+  constexpr void (*f())() {
+    void h();
+    return &h;
+  }
+  static_assert(f<int>() == f<char>(), "");
+  void h();
+  static_assert(f<int>() == &h, "");
+}
+
+namespace Test5 {
+  constexpr auto f() -> void (*)() {
+    void g();
+    struct X {
+      friend void g();
+      static constexpr auto h() -> void (*)() { return g; }
+    };
+    return X::h();
+  }
+  void g();
+  static_assert(f() == g, "");
+}