An auto variable can't appear in its own initializer.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74312 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 62e0eb3..aa8b240 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -398,6 +398,10 @@
 def note_uninit_reference_member : Note<
   "uninitialized reference member is here">;
 
+// C++0x auto
+def err_auto_variable_cannot_appear_in_own_initializer : Error<
+  "variable %0 declared with 'auto' type cannot appear in its own initializer">;
+  
 // Objective-C++
 def err_objc_decls_may_only_appear_in_global_scope : Error<
   "Objective-C declarations may only appear in global scope">;
diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
index d76cd24..4153661 100644
--- a/lib/AST/Type.cpp
+++ b/lib/AST/Type.cpp
@@ -964,6 +964,7 @@
   case NullPtr:           return "nullptr_t";
   case Overload:          return "<overloaded function type>";
   case Dependent:         return "<dependent type>";
+  case UndeducedAuto:     return "<undeduced auto type>";
   }
 }
 
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 3d22321..2f84306 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -627,6 +627,12 @@
 Sema::BuildDeclRefExpr(NamedDecl *D, QualType Ty, SourceLocation Loc,
                        bool TypeDependent, bool ValueDependent,
                        const CXXScopeSpec *SS) {
+  if (Context.getCanonicalType(Ty) == Context.UndeducedAutoTy) {
+    Diag(Loc,
+         diag::err_auto_variable_cannot_appear_in_own_initializer) 
+      << D->getDeclName();
+    return ExprError();
+  }
   
   if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
     if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(CurContext)) {
diff --git a/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p2.cpp b/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p2.cpp
new file mode 100644
index 0000000..8f5058e
--- /dev/null
+++ b/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p2.cpp
@@ -0,0 +1,4 @@
+// RUN: clang-cc -fsyntax-only -verify %s -std=c++0x
+void f() {
+  auto a = a; // expected-error{{variable 'a' declared with 'auto' type cannot appear in its own initializer}}
+}