[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, 19 insertions, 0 deletions

diff --git a/clang-tools-extra/docs/clang-tidy/checks/misc-forward-declaration-namespace.rst b/clang-tools-extra/docs/clang-tidy/checks/misc-forward-declaration-namespace.rst
new file mode 100644
index 00000000000..c8527b09fcd
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/misc-forward-declaration-namespace.rst
@@ -0,0 +1,19 @@
+.. title:: clang-tidy - misc-forward-declaration-namespace
+
+misc-forward-declaration-namespace
+==================================
+
+Checks if an unused forward declaration is in a wrong namespace.
+
+The check inspects all unused forward declarations and checks if there is any
+declaration/definition with the same name existing, which could indicate that
+the forward declaration is in a potentially wrong namespace.
+
+.. code:: c++
+  namespace na { struct A; }
+  namespace nb { struct A {}; }
+  nb::A a;
+  // warning : no definition found for 'A', but a definition with the same name
+  // 'A' found in another namespace 'nb::'
+
+This check can only generate warnings, but it can't suggest a fix at this point.