From aec2ac67e7190bdb88abb1d427b82ae3284ea756 Mon Sep 17 00:00:00 2001
From: Kaelyn Uhrain <rikka@google.com>
Date: Thu, 26 Apr 2012 23:36:17 +0000
Subject: [PATCH] Add note to help explain why a tag such as 'struct' is needed
 to refer to a given type, when the reason is that there is a non-type decl
 with the same name.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@155677 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticCommonKinds.td |  2 ++
 lib/Parse/ParseDecl.cpp                      | 16 ++++++++++++++--
 lib/Sema/SemaDecl.cpp                        |  8 ++++++++
 test/FixIt/fixit.cpp                         |  2 +-
 test/Parser/cxx-using-declaration.cpp        | 16 ++++++++++++++++
 5 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/include/clang/Basic/DiagnosticCommonKinds.td b/include/clang/Basic/DiagnosticCommonKinds.td
index 103fc00b40..c1c933198d 100644
--- a/include/clang/Basic/DiagnosticCommonKinds.td
+++ b/include/clang/Basic/DiagnosticCommonKinds.td
@@ -74,6 +74,8 @@ def err_module_cycle : Error<"cyclic dependency in module '%0': %1">,
 def warn_module_build : Warning<"building module '%0' from source">, 
   InGroup<ModuleBuild>, DefaultIgnore;
 def note_pragma_entered_here : Note<"#pragma entered here">;  
+def note_decl_shadowing_tag_type : Note<
+  "non-type %0 shadowing %1 %0 declared here">;
 
 // Sema && Lex
 def ext_longlong : Extension<
diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index 4775798d62..134bc97a1b 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -14,6 +14,7 @@
 #include "clang/Parse/Parser.h"
 #include "clang/Parse/ParseDiagnostic.h"
 #include "clang/Basic/OpenCL.h"
+#include "clang/Sema/Lookup.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/ParsedTemplate.h"
 #include "clang/Sema/PrettyDeclStackTrace.h"
@@ -1671,9 +1672,20 @@ bool Parser::ParseImplicitInt(DeclSpec &DS, CXXScopeSpec *SS,
     }
 
     if (TagName) {
+      IdentifierInfo *TokenName = Tok.getIdentifierInfo();
+      LookupResult R(Actions, TokenName, SourceLocation(),
+                     Sema::LookupOrdinaryName);
+
       Diag(Loc, diag::err_use_of_tag_name_without_tag)
-        << Tok.getIdentifierInfo() << TagName << getLangOpts().CPlusPlus
-        << FixItHint::CreateInsertion(Tok.getLocation(),FixitTagName);
+        << TokenName << TagName << getLangOpts().CPlusPlus
+        << FixItHint::CreateInsertion(Tok.getLocation(), FixitTagName);
+
+      if (Actions.LookupParsedName(R, getCurScope(), SS)) {
+        for (LookupResult::iterator I = R.begin(), IEnd = R.end();
+             I != IEnd; ++I)
+          Diag((*I)->getLocation(), diag::note_decl_shadowing_tag_type)
+            << TokenName << TagName;
+      }
 
       // Parse this as a tag as if the missing tag were present.
       if (TagKind == tok::kw_enum)
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 38bb852fa2..ec950d1842 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -564,6 +564,14 @@ Corrected:
         Diag(NameLoc, diag::err_use_of_tag_name_without_tag)
           << Name << TagName << getLangOpts().CPlusPlus
           << FixItHint::CreateInsertion(NameLoc, FixItTagName);
+
+        LookupResult R(*this, Name, NameLoc, LookupOrdinaryName);
+        if (LookupParsedName(R, S, &SS)) {
+          for (LookupResult::iterator I = R.begin(), IEnd = R.end();
+               I != IEnd; ++I)
+            Diag((*I)->getLocation(), diag::note_decl_shadowing_tag_type)
+              << Name << TagName;
+        }
         break;
       }
       
diff --git a/test/FixIt/fixit.cpp b/test/FixIt/fixit.cpp
index e6609d8a6c..9a2acd33e0 100644
--- a/test/FixIt/fixit.cpp
+++ b/test/FixIt/fixit.cpp
@@ -211,7 +211,7 @@ class Foo {
  public:
   enum Bar { X, Y };
   void SetBar(Bar bar);
-  Bar Bar();
+  Bar Bar(); // expected-note 2 {{non-type 'Bar' shadowing enum 'Bar' declared here}}
  private:
   Bar bar_; // expected-error {{must use 'enum' tag to refer to type 'Bar' in this scope}}
 };
diff --git a/test/Parser/cxx-using-declaration.cpp b/test/Parser/cxx-using-declaration.cpp
index 2b2a69d1a4..8c60b9b7a2 100644
--- a/test/Parser/cxx-using-declaration.cpp
+++ b/test/Parser/cxx-using-declaration.cpp
@@ -43,3 +43,19 @@ using F::X;
 // Should have some errors here.  Waiting for implementation.
 void X(int);
 struct X *x;
+
+
+namespace ShadowedTagNotes {
+
+namespace foo {
+  class Bar {};
+}
+
+void Bar(int); // expected-note{{non-type 'Bar' shadowing class 'Bar' declared here}}
+using foo::Bar;
+
+void ambiguity() {
+   const Bar *x; // expected-error{{must use 'class' tag to refer to type 'Bar' in this scope}}
+}
+
+} // namespace ShadowedTagNotes
-- 
2.40.0