Use an artifical namespace so that member vars do not hide local vars.

Summary:
While evaluating expressions when stopped in a class method, there was a
problem of member variables hiding local variables. This was happening
because, in the context of a method, clang already knew about member
variables with their name and assumed that they were the only variables
with those names in scope. Consequently, clang never checks with LLDB
about the possibility of local variables with the same name and goes
wrong. This change addresses the problem by using an artificial
namespace "$__lldb_local_vars". All local variables in scope are
declared in the "$__lldb_expr" method as follows:

    using $__lldb_local_vars::<local var 1>;
    using $__lldb_local_vars::<local var 2>;
    ...

This hides the member variables with the same name and forces clang to
enquire about the variables which it thinks are declared in
$__lldb_local_vars. When LLDB notices that clang is enquiring about
variables in $__lldb_local_vars, it looks up local vars and conveys
their information if found. This way, member variables do not hide local
variables, leading to correct evaluation of expressions.

A point to keep in mind is that the above solution does not solve the
problem for one specific case:

    namespace N
    {
        int a;
    }

    class A
    {
    public:
        void Method();
        int a;
    };

    void
    A::Method()
    {
        using N::a;
        ...

        // Since the above solution only touches locals, it does not
        // force clang to enquire about "a" coming from namespace N.
    }

Reviewers: clayborg, spyffe

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D16746

llvm-svn: 259810

12 files changed, 409 insertions, 13 deletions

diff --git a/lldb/include/lldb/Symbol/ClangASTContext.h b/lldb/include/lldb/Symbol/ClangASTContext.h
index bd3a113e6cc..3eb7446f6d0 100644
--- a/lldb/include/lldb/Symbol/ClangASTContext.h
+++ b/lldb/include/lldb/Symbol/ClangASTContext.h
@@ -422,6 +422,11 @@ public:
     GetUniqueNamespaceDeclaration (const char *name,
                                    clang::DeclContext *decl_ctx);
 
+    static clang::NamespaceDecl *
+    GetUniqueNamespaceDeclaration (clang::ASTContext *ast,
+                                   const char *name,
+                                   clang::DeclContext *decl_ctx);
+
     //------------------------------------------------------------------
     // Function Types
     //------------------------------------------------------------------
@@ -565,7 +570,9 @@ public:
     //----------------------------------------------------------------------
     
     std::vector<CompilerDecl>
-    DeclContextFindDeclByName (void *opaque_decl_ctx, ConstString name) override;
+    DeclContextFindDeclByName (void *opaque_decl_ctx,
+                               ConstString name,
+                               const bool ignore_using_decls) override;
 
     bool
     DeclContextIsStructUnionOrClass (void *opaque_decl_ctx) override;
diff --git a/lldb/include/lldb/Symbol/CompilerDeclContext.h b/lldb/include/lldb/Symbol/CompilerDeclContext.h
index 9135b44323b..7432adac613 100644
--- a/lldb/include/lldb/Symbol/CompilerDeclContext.h
+++ b/lldb/include/lldb/Symbol/CompilerDeclContext.h
@@ -66,7 +66,7 @@ public:
     IsClang () const;
 
     std::vector<CompilerDecl>
-    FindDeclByName (ConstString name);
+    FindDeclByName (ConstString name, const bool ignore_using_decls);
 
     //----------------------------------------------------------------------
     /// Checks if this decl context represents a method of a class.
diff --git a/lldb/include/lldb/Symbol/TypeSystem.h b/lldb/include/lldb/Symbol/TypeSystem.h
index 9b43b9dec37..7df974fcd32 100644
--- a/lldb/include/lldb/Symbol/TypeSystem.h
+++ b/lldb/include/lldb/Symbol/TypeSystem.h
@@ -143,7 +143,9 @@ public:
     //----------------------------------------------------------------------
     
     virtual std::vector<CompilerDecl>
-    DeclContextFindDeclByName (void *opaque_decl_ctx, ConstString name);
+    DeclContextFindDeclByName (void *opaque_decl_ctx,
+                               ConstString name,
+                               const bool ignore_imported_decls);
 
     virtual bool
     DeclContextIsStructUnionOrClass (void *opaque_decl_ctx) = 0;
diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/Makefile b/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/Makefile
new file mode 100644
index 00000000000..35eb63f922f
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/Makefile
@@ -0,0 +1,5 @@
+LEVEL = ../../../make
+
+CXX_SOURCES = main.cpp
+
+include $(LEVEL)/Makefile.rules
diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/TestMembersAndLocalsWithSameName.py b/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/TestMembersAndLocalsWithSameName.py
new file mode 100644
index 00000000000..12fc4c23637
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/TestMembersAndLocalsWithSameName.py
@@ -0,0 +1,197 @@
+import lldb
+from lldbsuite.test.lldbtest import *
+import lldbsuite.test.lldbutil as lldbutil
+
+class TestMembersAndLocalsWithSameName(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test_when_stopped_in_method(self):
+        self._load_exe()
+
+        # Set breakpoints
+        bp1 = self.target.BreakpointCreateBySourceRegex("Break 1", self.src_file_spec)
+        self.assertTrue(bp1.IsValid() and bp1.GetNumLocations() >= 1, VALID_BREAKPOINT)
+        bp2 = self.target.BreakpointCreateBySourceRegex("Break 2", self.src_file_spec)
+        self.assertTrue(bp2.IsValid() and bp2.GetNumLocations() >= 1, VALID_BREAKPOINT)
+        bp3 = self.target.BreakpointCreateBySourceRegex("Break 3", self.src_file_spec)
+        self.assertTrue(bp3.IsValid() and bp3.GetNumLocations() >= 1, VALID_BREAKPOINT)
+        bp4 = self.target.BreakpointCreateBySourceRegex("Break 4", self.src_file_spec)
+        self.assertTrue(bp4.IsValid() and bp4.GetNumLocations() >= 1, VALID_BREAKPOINT)
+
+        # Launch the process
+        self.process = self.target.LaunchSimple(None, None, self.get_process_working_directory())
+        self.assertTrue(self.process.IsValid(), PROCESS_IS_VALID)
+
+        self.assertTrue(self.process.GetState() == lldb.eStateStopped, PROCESS_STOPPED)
+
+        self._test_globals()
+
+        self.process.Continue()
+        self.assertTrue(self.process.GetState() == lldb.eStateStopped, PROCESS_STOPPED)
+        thread = lldbutil.get_stopped_thread(self.process, lldb.eStopReasonBreakpoint)
+        self.assertTrue(thread.IsValid())
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame.IsValid())
+
+        val = frame.EvaluateExpression("a");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 12345)
+
+        val = frame.EvaluateExpression("b");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 54321)
+
+        val = frame.EvaluateExpression("c");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 34567)
+
+        self.process.Continue()
+        self.assertTrue(self.process.GetState() == lldb.eStateStopped, PROCESS_STOPPED)
+        thread = lldbutil.get_stopped_thread(self.process, lldb.eStopReasonBreakpoint)
+        self.assertTrue(thread.IsValid())
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame.IsValid())
+
+        val = frame.EvaluateExpression("a");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 10001)
+
+        val = frame.EvaluateExpression("b");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 10002)
+
+        val = frame.EvaluateExpression("c");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 10003)
+
+        self.process.Continue()
+        self.assertTrue(self.process.GetState() == lldb.eStateStopped, PROCESS_STOPPED)
+        thread = lldbutil.get_stopped_thread(self.process, lldb.eStopReasonBreakpoint)
+        self.assertTrue(thread.IsValid())
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame.IsValid())
+
+        val = frame.EvaluateExpression("a");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 1)
+
+        val = frame.EvaluateExpression("b");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 2)
+
+        val = frame.EvaluateExpression("c");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 778899)
+
+    def test_when_stopped_in_function(self):
+        self._load_exe()
+
+        # Set breakpoints
+        bp1 = self.target.BreakpointCreateBySourceRegex("Break 1", self.src_file_spec)
+        self.assertTrue(bp1.IsValid() and bp1.GetNumLocations() >= 1, VALID_BREAKPOINT)
+        bp5 = self.target.BreakpointCreateBySourceRegex("Break 5", self.src_file_spec)
+        self.assertTrue(bp5.IsValid() and bp5.GetNumLocations() >= 1, VALID_BREAKPOINT)
+        bp6 = self.target.BreakpointCreateBySourceRegex("Break 6", self.src_file_spec)
+        self.assertTrue(bp6.IsValid() and bp6.GetNumLocations() >= 1, VALID_BREAKPOINT)
+        bp7 = self.target.BreakpointCreateBySourceRegex("Break 7", self.src_file_spec)
+        self.assertTrue(bp7.IsValid() and bp7.GetNumLocations() >= 1, VALID_BREAKPOINT)
+
+        # Launch the process
+        self.process = self.target.LaunchSimple(None, None, self.get_process_working_directory())
+        self.assertTrue(self.process.IsValid(), PROCESS_IS_VALID)
+
+        self.assertTrue(self.process.GetState() == lldb.eStateStopped, PROCESS_STOPPED)
+
+        self._test_globals()
+
+        self.process.Continue()
+        self.assertTrue(self.process.GetState() == lldb.eStateStopped, PROCESS_STOPPED)
+        thread = lldbutil.get_stopped_thread(self.process, lldb.eStopReasonBreakpoint)
+        self.assertTrue(thread.IsValid())
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame.IsValid())
+
+        val = frame.EvaluateExpression("a");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 12345)
+
+        val = frame.EvaluateExpression("b");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 54321)
+
+        val = frame.EvaluateExpression("c");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 34567)
+
+        self.process.Continue()
+        self.assertTrue(self.process.GetState() == lldb.eStateStopped, PROCESS_STOPPED)
+        thread = lldbutil.get_stopped_thread(self.process, lldb.eStopReasonBreakpoint)
+        self.assertTrue(thread.IsValid())
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame.IsValid())
+
+        val = frame.EvaluateExpression("a");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 10001)
+
+        val = frame.EvaluateExpression("b");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 10002)
+
+        val = frame.EvaluateExpression("c");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 10003)
+
+        self.process.Continue()
+        self.assertTrue(self.process.GetState() == lldb.eStateStopped, PROCESS_STOPPED)
+        thread = lldbutil.get_stopped_thread(self.process, lldb.eStopReasonBreakpoint)
+        self.assertTrue(thread.IsValid())
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame.IsValid())
+
+        val = frame.EvaluateExpression("a");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 1)
+
+        val = frame.EvaluateExpression("b");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 2)
+
+        val = frame.EvaluateExpression("c");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 778899)
+
+    def _load_exe(self):
+        self.build()
+
+        cwd = os.getcwd()
+
+        src_file = os.path.join(cwd, "main.cpp")
+        self.src_file_spec = lldb.SBFileSpec(src_file)
+        self.assertTrue(self.src_file_spec.IsValid(), "breakpoint file")
+
+        # Get the path of the executable
+        exe_path  = os.path.join(cwd, 'a.out')
+
+        # Load the executable
+        self.target = self.dbg.CreateTarget(exe_path)
+        self.assertTrue(self.target.IsValid(), VALID_TARGET)
+
+    def _test_globals(self):
+        thread = lldbutil.get_stopped_thread(self.process, lldb.eStopReasonBreakpoint)
+        self.assertTrue(thread.IsValid())
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame.IsValid())
+
+        val = frame.EvaluateExpression("a");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 112233)
+
+        val = frame.EvaluateExpression("b");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 445566)
+
+        val = frame.EvaluateExpression("c");
+        self.assertTrue(val.IsValid())
+        self.assertEqual(val.GetValueAsUnsigned(), 778899)
diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/main.cpp b/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/main.cpp
new file mode 100644
index 00000000000..baf08f6a983
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/member-and-local-vars-with-same-name/main.cpp
@@ -0,0 +1,73 @@
+namespace NN
+{
+  int a = 778899;
+  int b = 665544;
+  int c = 445566;
+}
+
+class A
+{
+public:
+  A();
+  int Method(int a, int b);
+
+private:
+  int a, b;
+};
+
+A::A() : a(10), b(100) { }
+
+int a = 112233;
+int b = 445566;
+int c = 778899;
+
+int
+A::Method(int a, int b)
+{
+    {
+        int a = 12345;
+        int b = 54321;
+        int c = 34567;
+        this->a = a + b + this->b; // Break 2
+    }
+
+    {
+        using namespace NN;
+        int a = 10001;
+        int b = 10002;
+        int c = 10003;
+        this->a = a + b + this->b; // Break 3
+    }
+
+    return this->a + this->b + a + b; // Break 4
+}
+
+int
+Function(int a, int b)
+{
+    int A;
+
+    {
+        int a = 12345;
+        int b = 54321;
+        int c = 34567;
+        A = a + b + c; // Break 5
+    }
+
+    {
+        using namespace NN;
+        int a = 10001;
+        int b = 10002;
+        int c = 10003;
+        A = a + b + c; // Break 6
+    }
+
+    return A + a + b; // Break 7
+}
+
+int
+main()
+{
+    A obj;
+    return obj.Method(1, 2) + Function(1, 2); // Break 1
+}
diff --git a/lldb/source/Expression/ExpressionSourceCode.cpp b/lldb/source/Expression/ExpressionSourceCode.cpp
index 93bac62c43c..13fdaf8dfeb 100644
--- a/lldb/source/Expression/ExpressionSourceCode.cpp
+++ b/lldb/source/Expression/ExpressionSourceCode.cpp
@@ -16,7 +16,9 @@
 #include "lldb/Symbol/DebugMacros.h"
 #include "lldb/Symbol/Block.h"
 #include "lldb/Symbol/TypeSystem.h"
+#include "lldb/Symbol/VariableList.h"
 #include "lldb/Target/ExecutionContext.h"
+#include "lldb/Target/Language.h"
 #include "lldb/Target/Platform.h"
 #include "lldb/Target/StackFrame.h"
 #include "lldb/Target/Target.h"
@@ -175,6 +177,21 @@ AddMacros(const DebugMacros *dm, CompileUnit *comp_unit, AddMacroState &state, S
     }
 }
 
+static void
+AddLocalVariableDecls(const lldb::VariableListSP &var_list_sp, StreamString &stream)
+{
+    for (size_t i = 0; i < var_list_sp->GetSize(); i++)
+    {
+        lldb::VariableSP var_sp = var_list_sp->GetVariableAtIndex(i);
+
+        ConstString var_name = var_sp->GetName();
+        if (var_name == ConstString("this"))
+            continue;
+
+        stream.Printf("using $__lldb_local_vars::%s;\n", var_name.AsCString());
+    }
+}
+
 bool ExpressionSourceCode::GetText (std::string &text, lldb::LanguageType wrapping_language, bool const_object, bool static_method, ExecutionContext &exe_ctx) const
 {
     const char *target_specific_defines = "typedef signed char BOOL;\n";
@@ -239,6 +256,7 @@ bool ExpressionSourceCode::GetText (std::string &text, lldb::LanguageType wrappi
     }
 
     StreamString debug_macros_stream;
+    StreamString lldb_local_var_decls;
     if (StackFrame *frame = exe_ctx.GetFramePtr())
     {
         const SymbolContext &sc = frame->GetSymbolContext(
@@ -253,8 +271,15 @@ bool ExpressionSourceCode::GetText (std::string &text, lldb::LanguageType wrappi
                 AddMacros(dm, sc.comp_unit, state, debug_macros_stream);
             }
         }
+
+        ConstString object_name;
+        if (Language::LanguageIsCPlusPlus(frame->GetLanguage()))
+        {
+            lldb::VariableListSP var_list_sp = frame->GetInScopeVariableList(false);
+            AddLocalVariableDecls(var_list_sp, lldb_local_var_decls);
+        }
     }
-    
+
     if (m_wrap)
     {
         switch (wrapping_language) 
@@ -284,19 +309,23 @@ bool ExpressionSourceCode::GetText (std::string &text, lldb::LanguageType wrappi
             wrap_stream.Printf("void                           \n"
                                "%s(void *$__lldb_arg)          \n"
                                "{                              \n"
+                               "    %s;                        \n"
                                "    %s;                        \n" 
                                "}                              \n",
                                m_name.c_str(),
+                               lldb_local_var_decls.GetData(),
                                m_body.c_str());
             break;
         case lldb::eLanguageTypeC_plus_plus:
             wrap_stream.Printf("void                                   \n"
                                "$__lldb_class::%s(void *$__lldb_arg) %s\n"
                                "{                                      \n"
+                               "    %s;                                \n"
                                "    %s;                                \n" 
                                "}                                      \n",
                                m_name.c_str(),
                                (const_object ? "const" : ""),
+                               lldb_local_var_decls.GetData(),
                                m_body.c_str());
             break;
         case lldb::eLanguageTypeObjC:
@@ -339,6 +368,6 @@ bool ExpressionSourceCode::GetText (std::string &text, lldb::LanguageType wrappi
     {
         text.append(m_body);
     }
-    
+
     return true;
 }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
index f4d6b195c7f..6092efa484f 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
@@ -57,6 +57,11 @@ using namespace lldb;
 using namespace lldb_private;
 using namespace clang;
 
+namespace
+{
+    const char *g_lldb_local_vars_namespace_cstr = "$__lldb_local_vars";
+} // anonymous namespace
+
 ClangExpressionDeclMap::ClangExpressionDeclMap (bool keep_result_in_memory,
                                                 Materializer::PersistentVariableDelegate *result_delegate,
                                                 ExecutionContext &exe_ctx) :
@@ -1004,6 +1009,24 @@ ClangExpressionDeclMap::FindGlobalVariable
     return VariableSP();
 }
 
+ClangASTContext *
+ClangExpressionDeclMap::GetClangASTContext ()
+{
+    StackFrame *frame = m_parser_vars->m_exe_ctx.GetFramePtr();
+    if (frame == nullptr)
+        return nullptr;
+
+    SymbolContext sym_ctx = frame->GetSymbolContext(lldb::eSymbolContextFunction|lldb::eSymbolContextBlock);
+    if (sym_ctx.block == nullptr)
+        return nullptr;
+
+    CompilerDeclContext frame_decl_context = sym_ctx.block->GetDeclContext();
+    if (!frame_decl_context)
+        return nullptr;
+
+    return llvm::dyn_cast_or_null<ClangASTContext>(frame_decl_context.GetTypeSystem());
+}
+
 // Interface for ClangASTSource
 
 void
@@ -1039,6 +1062,13 @@ ClangExpressionDeclMap::FindExternalVisibleDecls (NameSearchContext &context)
 
     if (const NamespaceDecl *namespace_context = dyn_cast<NamespaceDecl>(context.m_decl_context))
     {
+        if (namespace_context->getName().str() == std::string(g_lldb_local_vars_namespace_cstr))
+        {
+            CompilerDeclContext compiler_decl_ctx(GetClangASTContext(), (void*)context.m_decl_context);
+            FindExternalVisibleDecls(context, lldb::ModuleSP(), compiler_decl_ctx, current_id);
+            return;
+        }
+
         ClangASTImporter::NamespaceMapSP namespace_map = m_ast_importer_sp->GetNamespaceMap(namespace_context);
 
         if (log && log->GetVerbose())
@@ -1335,6 +1365,32 @@ ClangExpressionDeclMap::FindExternalVisibleDecls (NameSearchContext &context,
             return;
         }
 
+        if (name == ConstString(g_lldb_local_vars_namespace_cstr))
+        {
+            CompilerDeclContext frame_decl_context = sym_ctx.block != nullptr ?
+                                                     sym_ctx.block->GetDeclContext() :
+                                                     CompilerDeclContext();
+
+            if (frame_decl_context)
+            {
+                ClangASTContext *ast = llvm::dyn_cast_or_null<ClangASTContext>(frame_decl_context.GetTypeSystem());
+
+                if (ast)
+                {
+                    clang::NamespaceDecl *namespace_decl = ClangASTContext::GetUniqueNamespaceDeclaration(
+                        m_ast_context, name_unique_cstr, nullptr);
+                    if (namespace_decl)
+                    {
+                        context.AddNamedDecl(namespace_decl);
+                        clang::DeclContext *clang_decl_ctx = clang::Decl::castToDeclContext(namespace_decl);
+                        clang_decl_ctx->setHasExternalVisibleStorage(true);
+                    }
+                }
+            }
+
+            return;
+        }
+
         // any other $__lldb names should be weeded out now
         if (!::strncmp(name_unique_cstr, "$__lldb", sizeof("$__lldb") - 1))
             return;
@@ -1403,19 +1459,23 @@ ClangExpressionDeclMap::FindExternalVisibleDecls (NameSearchContext &context,
         ValueObjectSP valobj;
         VariableSP var;
 
-        if (frame && !namespace_decl)
+        bool local_var_lookup = !namespace_decl ||
+                                (namespace_decl.GetName() == ConstString(g_lldb_local_vars_namespace_cstr));
+        if (frame && local_var_lookup)
         {
             CompilerDeclContext compiler_decl_context = sym_ctx.block != nullptr ? sym_ctx.block->GetDeclContext() : CompilerDeclContext();
 
             if (compiler_decl_context)
             {
-                // Make sure that the variables are parsed so that we have the declarations
+                // Make sure that the variables are parsed so that we have the declarations.
                 VariableListSP vars = frame->GetInScopeVariableList(true);
                 for (size_t i = 0; i < vars->GetSize(); i++)
                     vars->GetVariableAtIndex(i)->GetDecl();
 
-                // Search for declarations matching the name
-                std::vector<CompilerDecl> found_decls = compiler_decl_context.FindDeclByName(name);
+                // Search for declarations matching the name. Do not include imported decls
+                // in the search if we are looking for decls in the artificial namespace
+                // $__lldb_local_vars.
+                std::vector<CompilerDecl> found_decls = compiler_decl_context.FindDeclByName(name, namespace_decl.IsValid());
                 
                 bool variable_found = false;
                 for (CompilerDecl decl : found_decls)
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
index b3f890c7acc..35833e87558 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
@@ -707,6 +707,9 @@ private:
     AddThisType(NameSearchContext &context,
                 TypeFromUser &type,
                 unsigned int current_id);
+
+    ClangASTContext *
+    GetClangASTContext();
 };
     
 } // namespace lldb_private
diff --git a/lldb/source/Symbol/ClangASTContext.cpp b/lldb/source/Symbol/ClangASTContext.cpp
index 0fc1a94876b..f953ddb21e4 100644
--- a/lldb/source/Symbol/ClangASTContext.cpp
+++ b/lldb/source/Symbol/ClangASTContext.cpp
@@ -1885,6 +1885,17 @@ ClangASTContext::GetUniqueNamespaceDeclaration (const char *name, DeclContext *d
     return namespace_decl;
 }
 
+NamespaceDecl *
+ClangASTContext::GetUniqueNamespaceDeclaration (clang::ASTContext *ast,
+                                                const char *name,
+                                                clang::DeclContext *decl_ctx)
+{
+    ClangASTContext *ast_ctx = ClangASTContext::GetASTContext(ast);
+    if (ast_ctx == nullptr)
+        return nullptr;
+
+    return ast_ctx->GetUniqueNamespaceDeclaration(name, decl_ctx);
+}
 
 clang::BlockDecl *
 ClangASTContext::CreateBlockDeclaration (clang::DeclContext *ctx)
@@ -9781,7 +9792,9 @@ ClangASTContext::DeclGetFunctionArgumentType (void *opaque_decl, size_t idx)
 //----------------------------------------------------------------------
 
 std::vector<CompilerDecl>
-ClangASTContext::DeclContextFindDeclByName(void *opaque_decl_ctx, ConstString name)
+ClangASTContext::DeclContextFindDeclByName(void *opaque_decl_ctx,
+                                           ConstString name,
+                                           const bool ignore_using_decls)
 {
     std::vector<CompilerDecl> found_decls;
     if (opaque_decl_ctx)
@@ -9805,12 +9818,16 @@ ClangASTContext::DeclContextFindDeclByName(void *opaque_decl_ctx, ConstString na
                 {
                     if (clang::UsingDirectiveDecl *ud = llvm::dyn_cast<clang::UsingDirectiveDecl>(child))
                     {
+                        if (ignore_using_decls)
+                            continue;
                         clang::DeclContext *from = ud->getCommonAncestor();
                         if (searched.find(ud->getNominatedNamespace()) == searched.end())
                             search_queue.insert(std::make_pair(from, ud->getNominatedNamespace()));
                     }
                     else if (clang::UsingDecl *ud = llvm::dyn_cast<clang::UsingDecl>(child))
                     {
+                        if (ignore_using_decls)
+                            continue;
                         for (clang::UsingShadowDecl *usd : ud->shadows())
                         {
                             clang::Decl *target = usd->getTargetDecl();
diff --git a/lldb/source/Symbol/CompilerDeclContext.cpp b/lldb/source/Symbol/CompilerDeclContext.cpp
index 8bee1b48753..10a70d97f23 100644
--- a/lldb/source/Symbol/CompilerDeclContext.cpp
+++ b/lldb/source/Symbol/CompilerDeclContext.cpp
@@ -15,10 +15,11 @@
 using namespace lldb_private;
 
 std::vector<CompilerDecl>
-CompilerDeclContext::FindDeclByName (ConstString name)
+CompilerDeclContext::FindDeclByName (ConstString name, const bool ignore_using_decls)
 {
     if (IsValid())
-        return m_type_system->DeclContextFindDeclByName(m_opaque_decl_ctx, name);
+        return m_type_system->DeclContextFindDeclByName(
+            m_opaque_decl_ctx, name, ignore_using_decls);
     else
         return std::vector<CompilerDecl>();
 }
diff --git a/lldb/source/Symbol/TypeSystem.cpp b/lldb/source/Symbol/TypeSystem.cpp
index 5c2ab5cceab..5b8e935c71d 100644
--- a/lldb/source/Symbol/TypeSystem.cpp
+++ b/lldb/source/Symbol/TypeSystem.cpp
@@ -153,7 +153,9 @@ TypeSystem::DeclGetFunctionArgumentType (void *opaque_decl, size_t arg_idx)
 
 
 std::vector<CompilerDecl>
-TypeSystem::DeclContextFindDeclByName (void *opaque_decl_ctx, ConstString name)
+TypeSystem::DeclContextFindDeclByName (void *opaque_decl_ctx,
+                                       ConstString name,
+                                       bool ignore_imported_decls)
 {
     return std::vector<CompilerDecl>();
 }