diff --git a/src/analyzer/code_analyzer.py b/src/analyzer/code_analyzer.py
index a0c49e4..c6ee048 100644
--- a/src/analyzer/code_analyzer.py
+++ b/src/analyzer/code_analyzer.py
@@ -119,10 +119,29 @@ def _analyze_hot_paths(self, tree: ast.AST) -> None:
     def _infer_expression_type(self, expr: ast.AST) -> str:
         """Backward compatibility method for tests."""
         return self.type_analyzer._infer_expression_type(expr) or 'auto'
-    
+
     def _get_type_name(self, node: ast.AST) -> str:
         """Backward compatibility method for tests."""
         return self.type_analyzer._annotation_to_cpp_type(node) or 'auto'
+
+    def _infer_variable_type(self, node: ast.Assign) -> None:
+        """Backward compatibility method for tests."""
+        self.type_analyzer._infer_variable_type(node)
+        # Update local type_info from the analyzer
+        for var_name, var_type in self.type_analyzer.type_info.items():
+            if isinstance(var_type, str):  # Only copy simple type strings
+                if not hasattr(self, 'type_info'):
+                    self.type_info = {}
+                self.type_info[var_name] = var_type
+
+    def _infer_function_types(self, node: ast.FunctionDef) -> None:
+        """Backward compatibility method for tests."""
+        self.type_analyzer._analyze_function_types(node)
+        # Update local type_info from the analyzer
+        for var_name, var_type in self.type_analyzer.type_info.items():
+            if not hasattr(self, 'type_info'):
+                self.type_info = {}
+            self.type_info[var_name] = var_type
     
     def _find_containing_function_or_class(self, target_node: ast.AST, tree: ast.AST) -> Optional[str]:
         """Find the function or class containing a given node."""
diff --git a/src/analyzer/performance_analyzer.py b/src/analyzer/performance_analyzer.py
index 13ecfcb..d77c726 100644
--- a/src/analyzer/performance_analyzer.py
+++ b/src/analyzer/performance_analyzer.py
@@ -74,10 +74,11 @@ def _analyze_loop_performance(self, node: ast.AST) -> None:
         if isinstance(node, (ast.For, ast.While)):
             # Check for nested loops
             nested_loops = self._count_nested_loops(node)
-            if nested_loops > 2:
+            if nested_loops > 1:  # Detect nested loops (2+ levels)
                 line = getattr(node, 'lineno', 0)
                 self.performance_bottlenecks.append({
                     'type': 'nested_loops',
+                    'description': f'Nested loop detected with {nested_loops} levels of nesting',
                     'nesting_level': nested_loops,
                     'line': line,
                     'suggestion': 'Consider algorithm optimization to reduce nesting'
@@ -87,12 +88,27 @@ def _analyze_loop_performance(self, node: ast.AST) -> None:
             expensive_ops = self._find_expensive_operations_in_loop(node)
             if expensive_ops:
                 line = getattr(node, 'lineno', 0)
-                self.performance_bottlenecks.append({
-                    'type': 'expensive_loop_operations',
-                    'operations': expensive_ops,
-                    'line': line,
-                    'suggestion': 'Move expensive operations outside the loop when possible'
-                })
+
+                # Check specifically for container modifications
+                container_ops = [op for op in expensive_ops if op in ['append', 'extend', 'insert']]
+                if container_ops:
+                    self.performance_bottlenecks.append({
+                        'type': 'container_modification',
+                        'description': f'Container modification in loop: {", ".join(container_ops)}',
+                        'operations': container_ops,
+                        'line': line,
+                        'suggestion': 'Consider pre-allocating containers or using list comprehensions'
+                    })
+
+                # Check for other expensive operations
+                other_ops = [op for op in expensive_ops if op not in ['append', 'extend', 'insert']]
+                if other_ops:
+                    self.performance_bottlenecks.append({
+                        'type': 'expensive_loop_operations',
+                        'operations': other_ops,
+                        'line': line,
+                        'suggestion': 'Move expensive operations outside the loop when possible'
+                    })
     
     def _analyze_comprehension_performance(self, node: ast.ListComp) -> None:
         """Analyze list comprehension performance."""
diff --git a/src/analyzer/type_inference.py b/src/analyzer/type_inference.py
index cb01a73..caf71ba 100644
--- a/src/analyzer/type_inference.py
+++ b/src/analyzer/type_inference.py
@@ -154,6 +154,8 @@ def _infer_expression_type(self, expr: ast.AST) -> Optional[str]:
                 result = 'double'
             elif isinstance(expr.value, str):
                 result = 'std::string'
+            elif expr.value is None:
+                result = 'std::nullptr_t'
         elif isinstance(expr, ast.List):
             if expr.elts:
                 element_type = self._infer_expression_type(expr.elts[0])
@@ -190,6 +192,12 @@ def _infer_expression_type(self, expr: ast.AST) -> Optional[str]:
                 result = 'int'
             else:
                 result = 'auto'
+        elif isinstance(expr, ast.Compare):
+            # Comparison operations always return bool
+            result = 'bool'
+        elif isinstance(expr, ast.BoolOp):
+            # Boolean operations (and, or) always return bool
+            result = 'bool'
         elif isinstance(expr, ast.ListComp):
             # List comprehension - infer from element type
             element_type = self._infer_expression_type(expr.elt)
@@ -231,5 +239,17 @@ def _analyze_function_types(self, node: ast.FunctionDef) -> None:
             return_type = self._annotation_to_cpp_type(node.returns)
             if return_type:
                 func_info['return_type'] = return_type
+        else:
+            # Try to infer return type from return statements
+            inferred_return_type = self._infer_return_type_from_body(node.body)
+            if inferred_return_type:
+                func_info['return_type'] = inferred_return_type
         
-        self.type_info[node.name] = func_info
\ No newline at end of file
+        self.type_info[node.name] = func_info
+
+    def _infer_return_type_from_body(self, body: List[ast.stmt]) -> Optional[str]:
+        """Infer return type by analyzing return statements in function body."""
+        for node in ast.walk(ast.Module(body=body, type_ignores=[])):
+            if isinstance(node, ast.Return) and node.value:
+                return self._infer_expression_type(node.value)
+        return None
\ No newline at end of file