Add co_names to BoxedCode object.

This field not used very often. So use this lazy way, just retrive
it from bytecode when needed. Add a field to BoxedCode will increase
 the memory usage.

src/runtime/code.cpp

@@ -16,6 +16,8 @@
 #include <sstream>
 
 #include "codegen/baseline_jit.h"
+#include "core/bst.h"
+#include "core/cfg.h"
 #include "runtime/objmodel.h"
 #include "runtime/set.h"
 
@@ -101,6 +103,43 @@ Box* BoxedCode::flags(Box* b, void*) noexcept {
     return boxInt(flags);
 }
 
+Box* BoxedCode::co_names(Box* b, void*) noexcept {
+    RELEASE_ASSERT(b->cls == code_cls, "");
+    BoxedCode* code = static_cast<BoxedCode*>(b);
+
+    BoxedSet* names = (BoxedSet*)createSet();
+    for (auto block : code->source->cfg->blocks) {
+        for (BST_stmt* stmt : *block) {
+            if (stmt->type() == BST_TYPE::LoadName && bst_cast<BST_LoadName>(stmt)->lookup_type != ScopeInfo::VarScopeType::FAST) {
+                PySet_Add(names, code->code_constants.getConstant(bst_cast<BST_LoadName>(stmt)->index_id));
+            }
+            else if (stmt->type() == BST_TYPE::StoreName && bst_cast<BST_StoreName>(stmt)->lookup_type != ScopeInfo::VarScopeType::FAST) {
+                PySet_Add(names, code->code_constants.getConstant(bst_cast<BST_StoreName>(stmt)->index_id));
+            }
+            else if (stmt->type() == BST_TYPE::DeleteName && bst_cast<BST_DeleteName>(stmt)->lookup_type != ScopeInfo::VarScopeType::FAST) {
+                PySet_Add(names, code->code_constants.getConstant(bst_cast<BST_DeleteName>(stmt)->index_id));
+            }
+            else if (stmt->type() == BST_TYPE::LoadAttr) {
+                PySet_Add(names, code->code_constants.getConstant(bst_cast<BST_LoadAttr>(stmt)->index_attr));
+            }
+            else if (stmt->type() == BST_TYPE::StoreAttr) {
+                PySet_Add(names, code->code_constants.getConstant(bst_cast<BST_StoreAttr>(stmt)->index_attr));
+            }
+            else if (stmt->type() == BST_TYPE::DeleteAttr) {
+                PySet_Add(names, code->code_constants.getConstant(bst_cast<BST_DeleteAttr>(stmt)->index_attr));
+            }
+            else if (stmt->type() == BST_TYPE::ImportFrom) {
+                PySet_Add(names, code->code_constants.getConstant(bst_cast<BST_ImportFrom>(stmt)->index_id));
+            }
+            else if (stmt->type() == BST_TYPE::ImportName) {
+                PySet_Add(names, code->code_constants.getConstant(bst_cast<BST_ImportName>(stmt)->index_id));
+            }
+        }
+    }
+
+    return PySequence_Tuple(names);
+}
+
 void BoxedCode::dealloc(Box* b) noexcept {
     BoxedCode* o = static_cast<BoxedCode*>(b);
 
@@ -260,6 +299,7 @@ void setupCode() {
     code_cls->giveAttrBorrowed("__new__", Py_None); // Hacky way of preventing users from instantiating this
 
     code_cls->giveAttrDescriptor("co_name", BoxedCode::co_name, NULL);
+    code_cls->giveAttrDescriptor("co_names", BoxedCode::co_names, NULL);
     code_cls->giveAttrDescriptor("co_filename", BoxedCode::co_filename, NULL);
     code_cls->giveAttrDescriptor("co_firstlineno", BoxedCode::co_firstlineno, NULL);
     code_cls->giveAttrDescriptor("co_argcount", BoxedCode::argcount, NULL);

src/runtime/types.h

@@ -1195,6 +1195,7 @@ public:
     // static BORROWED(Box*) name(Box* b, void*) noexcept;
     // static BORROWED(Box*) filename(Box* b, void*) noexcept;
     static Box* co_name(Box* b, void*) noexcept;
+    static Box* co_names(Box* b, void*) noexcept;
     static Box* co_filename(Box* b, void*) noexcept;
     static Box* co_firstlineno(Box* b, void*) noexcept;
     static Box* argcount(Box* b, void*) noexcept;