[clang-tidy] Added a check for forward declaration in the potentially wrong namespace

Adds a new check "misc-forward-declaration-namespace".
In check, A forward declaration is considerred in a potentially wrong namespace
if there is any definition/declaration with the same name exists in a different
namespace.

Reviewers: akuegel, hokein, alexfh

Patch by Eric Liu!

Differential Revision: http://reviews.llvm.org/D17195

llvm-svn: 261737

1 files changed, 163 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/misc-forward-declaration-namespace.cpp b/clang-tools-extra/test/clang-tidy/misc-forward-declaration-namespace.cpp
new file mode 100644
index 00000000000..b427a185f6c
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/misc-forward-declaration-namespace.cpp
@@ -0,0 +1,163 @@
+// RUN: %check_clang_tidy %s misc-forward-declaration-namespace %t 
+
+namespace {
+// This is a declaration in a wrong namespace.
+class T_A;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration 'T_A' is never referenced, but a declaration with the same name found in another namespace 'na' [misc-forward-declaration-namespace]
+// CHECK-MESSAGES: note: a declaration of 'T_A' is found here
+// CHECK-MESSAGES: :[[@LINE-3]]:7: warning: no definition found for 'T_A', but a definition with the same name 'T_A' found in another namespace '(global)' [misc-forward-declaration-namespace]
+// CHECK-MESSAGES: note: a definition of 'T_A' is found here
+}
+
+namespace na {
+// This is a declaration in a wrong namespace.
+class T_A;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration 'T_A' is never referenced, but a declaration with the same name found in another namespace '(anonymous)'
+// CHECK-MESSAGES: note: a declaration of 'T_A' is found here
+// CHECK-MESSAGES: :[[@LINE-3]]:7: warning: no definition found for 'T_A', but a definition with the same name 'T_A' found in another namespace '(global)'
+// CHECK-MESSAGES: note: a definition of 'T_A' is found here
+}
+
+class T_A;
+
+class T_A {
+  int x;
+};
+
+class NESTED;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: no definition found for 'NESTED', but a definition with the same name 'NESTED' found in another namespace '(anonymous namespace)::nq::(anonymous)'
+// CHECK-MESSAGES: note: a definition of 'NESTED' is found here
+
+namespace {
+namespace nq {
+namespace {
+class NESTED {};
+}
+}
+}
+
+namespace na {
+class T_B;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration 'T_B' is never referenced, but a declaration with the same name found in another namespace 'nb'
+// CHECK-MESSAGES: note: a declaration of 'T_B' is found here
+// CHECK-MESSAGES: :[[@LINE-3]]:7: warning: no definition found for 'T_B', but a definition with the same name 'T_B' found in another namespace 'nb'
+// CHECK-MESSAGES: note: a definition of 'T_B' is found here
+}
+
+namespace nb {
+class T_B;
+}
+
+namespace nb {
+class T_B {
+  int x;
+};
+}
+
+namespace na {
+class T_B;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration 'T_B' is never referenced, but a declaration with the same name found in another namespace 'nb'
+// CHECK-MESSAGES: note: a declaration of 'T_B' is found here
+// CHECK-MESSAGES: :[[@LINE-3]]:7: warning: no definition found for 'T_B', but a definition with the same name 'T_B' found in another namespace 'nb'
+// CHECK-MESSAGES: note: a definition of 'T_B' is found here
+}
+
+// A simple forward declaration. Although it is never used, but no declaration
+// with the same name is found in other namespace.
+class OUTSIDER;
+
+namespace na {
+// This class is referenced declaration, we don't generate warning.
+class OUTSIDER_1;
+}
+
+void f(na::OUTSIDER_1);
+
+namespace nc {
+// This class is referenced as friend in OOP.
+class OUTSIDER_1;
+
+class OOP {
+  friend struct OUTSIDER_1;
+};
+}
+
+namespace nd {
+class OUTSIDER_1;
+void f(OUTSIDER_1 *);
+}
+
+namespace nb {
+class OUTSIDER_1;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration 'OUTSIDER_1' is never referenced, but a declaration with the same name found in another namespace 'na'
+// CHECK-MESSAGES: note: a declaration of 'OUTSIDER_1' is found here
+}
+
+
+namespace na {
+template<typename T>
+class T_C;
+}
+
+namespace nb {
+// FIXME: this is an error, but we don't consider template class declaration
+// now.
+template<typename T>
+class T_C;
+}
+
+namespace na {
+template<typename T>
+class T_C {
+  int x;
+};
+}
+
+namespace na {
+
+template <typename T>
+class T_TEMP {
+  template <typename _Tp1>
+  struct rebind { typedef T_TEMP<_Tp1> other; };
+};
+
+// We ignore class template specialization.
+template class T_TEMP<char>;
+}
+
+namespace nb {
+
+template <typename T>
+class T_TEMP_1 {
+  template <typename _Tp1>
+  struct rebind { typedef T_TEMP_1<_Tp1> other; };
+};
+
+// We ignore class template specialization.
+extern template class T_TEMP_1<char>;
+}
+
+namespace nd {
+class D;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration 'D' is never referenced, but a declaration with the same name found in another namespace 'nd::ne'
+// CHECK-MESSAGES: note: a declaration of 'D' is found here
+}
+
+namespace nd {
+namespace ne {
+class D;
+}
+}
+
+int f(nd::ne::D &d);
+
+
+// This should be ignored by the check.
+template <typename... Args>
+class Observer {
+  class Impl;
+};
+
+template <typename... Args>
+class Observer<Args...>::Impl {
+};