Fixed placement of module level typeguard imports

Fixes #385.

Author: agronholm

docs/versionhistory.rst

@@ -9,6 +9,8 @@ This library adheres to `Semantic Versioning 2.0 <https://semver.org/#semantic-v
 - Fixed ``@typechecked`` optimization causing compilation of instrumented code to fail
   when any block was left empty by the AST transformer (eg `if` or `try` / `except` blocks)
   (`#352 <https://github.com/agronholm/typeguard/issues/352>`_)
+- Fixed placement of injected typeguard imports with respect to ``__future__`` imports and module
+  docstrings (`#385 <https://github.com/agronholm/typeguard/issues/385>`_)
 
 **4.1.2** (2023-08-18)
 

src/typeguard/_transformer.py

@@ -608,8 +608,9 @@ def visit_Name(self, node: Name) -> Name:
         return node
 
     def visit_Module(self, node: Module) -> Module:
+        self._module_memo = self._memo = TransformMemo(node, None, ())
         self.generic_visit(node)
-        self._memo.insert_imports(node)
+        self._module_memo.insert_imports(node)
 
         fix_missing_locations(node)
         return node

tests/test_transformer.py

@@ -1624,3 +1624,34 @@ def foo() -> int:
             '''
         ).strip()
     )
+
+
+def test_respect_future_import() -> None:
+    # Regression test for #385
+    node = parse(
+        dedent(
+            '''
+            """module docstring"""
+            from __future__ import annotations
+
+            def foo() -> int:
+                return 1
+            '''
+        )
+    )
+    TypeguardTransformer().visit(node)
+    assert (
+        unparse(node)
+        == dedent(
+            '''
+            """module docstring"""
+            from __future__ import annotations
+            from typeguard import TypeCheckMemo
+            from typeguard._functions import check_return_type
+
+            def foo() -> int:
+                memo = TypeCheckMemo(globals(), locals())
+                return check_return_type('foo', 1, int, memo)
+            '''
+        ).strip()
+    )