skip expression statements that are constant strings (docstrings)

src/codegen/ast_interpreter.cpp

@@ -611,7 +611,11 @@ Value ASTInterpreter::visit_stmt(AST_stmt* node) {
         case AST_TYPE::Delete:
             return visit_delete((AST_Delete*)node);
         case AST_TYPE::Expr:
-            return visit_expr((AST_Expr*)node);
+            // docstrings are str constant expression statements.
+            // ignore those while interpreting.
+            if ((((AST_Expr*)node)->value)->type != AST_TYPE::Str)
+                return visit_expr((AST_Expr*)node);
+            break;
         case AST_TYPE::FunctionDef:
             return visit_functionDef((AST_FunctionDef*)node);
         case AST_TYPE::Pass:

src/codegen/irgen/irgenerator.cpp

@@ -1991,7 +1991,8 @@ private:
                 doDelete(ast_cast<AST_Delete>(node), unw_info);
                 break;
             case AST_TYPE::Expr:
-                doExpr(ast_cast<AST_Expr>(node), unw_info);
+                if ((((AST_Expr*)node)->value)->type != AST_TYPE::Str)
+                    doExpr(ast_cast<AST_Expr>(node), unw_info);
                 break;
             case AST_TYPE::FunctionDef:
                 doFunctionDef(ast_cast<AST_FunctionDef>(node), unw_info);