# Buggy code
def execute_touch(path, follow):
    b_path = to_bytes(path, errors="surrogate_or_strict")
    prev_state = get_state(b_path)

    if not module.check_mode:
        if prev_state == "absent":
            # Create an empty file if the filename did not already exist
            try:
                open(b_path, "wb").close()
            except (OSError, IOError) as e:
                raise AnsibleModuleError(
                    results={
                        "msg": "Error, could not touch target: %s"
                        % to_native(e, nonstring="simplerepr"),
                        "path": path,
                    }
                )

        elif prev_state in ("file", "directory", "hard"):
            # Update the timestamp if the file already existed
            try:
                os.utime(b_path, None)
            except OSError as e:
                raise AnsibleModuleError(
                    results={
                        "msg": "Error while touching existing target: %s"
                        % to_native(e, nonstring="simplerepr"),
                        "path": path,
                    }
                )

        elif prev_state == "link" and follow:
            # Update the timestamp of the pointed to file
            b_link_target = os.readlink(b_path)
            try:
                os.utime(b_link_target, None)
            except OSError as e:
                raise AnsibleModuleError(
                    results={
                        "msg": "Error while touching existing target: %s"
                        % to_native(e, nonstring="simplerepr"),
                        "path": path,
                    }
                )

        else:
            raise AnsibleModuleError(
                results={
                    "msg": "Can only touch files, directories, and"
                    " hardlinks (%s is %s)" % (path, prev_state)
                }
            )

        # Update the attributes on the file
        diff = initial_diff(path, "touch", prev_state)
        file_args = module.load_file_common_arguments(module.params)
        try:
            module.set_fs_attributes_if_different(file_args, True, diff, expand=False)
        except SystemExit as e:
            if e.code:
                # We take this to mean that fail_json() was called from
                # somewhere in basic.py
                if prev_state == "absent":
                    # If we just created the file we can safely remove it
                    os.remove(b_path)
            raise

    # Unfortunately, touch always changes the file because it updates file's timestamp
    return {"dest": path, "changed": True, "diff": diff}


# Traceback (UnboundLocalError)
The full traceback is:
Traceback (most recent call last):
File "/tmp/ansible_mz6qwS/ansible_module_file.py", line 739, in <module>
main()
File "/tmp/ansible_mz6qwS/ansible_module_file.py", line 731, in main
result = execute_touch(path, follow)
File "/tmp/ansible_mz6qwS/ansible_module_file.py", line 373, in execute_touch
return {'dest': path, 'changed': True, 'diff': diff}
UnboundLocalError: local variable 'diff' referenced before assignment

# Fixed code
def execute_touch(path, follow):
    b_path = to_bytes(path, errors="surrogate_or_strict")
    prev_state = get_state(b_path)

    # Unfortunately, touch always changes the file because it updates file's timestamp
    result = {"dest": path, "changed": True}

    if not module.check_mode:
        if prev_state == "absent":
            # Create an empty file if the filename did not already exist
            try:
                open(b_path, "wb").close()
            except (OSError, IOError) as e:
                raise AnsibleModuleError(
                    results={
                        "msg": "Error, could not touch target: %s"
                        % to_native(e, nonstring="simplerepr"),
                        "path": path,
                    }
                )

        elif prev_state in ("file", "directory", "hard"):
            # Update the timestamp if the file already existed
            try:
                os.utime(b_path, None)
            except OSError as e:
                raise AnsibleModuleError(
                    results={
                        "msg": "Error while touching existing target: %s"
                        % to_native(e, nonstring="simplerepr"),
                        "path": path,
                    }
                )

        elif prev_state == "link" and follow:
            # Update the timestamp of the pointed to file
            b_link_target = os.readlink(b_path)
            try:
                os.utime(b_link_target, None)
            except OSError as e:
                raise AnsibleModuleError(
                    results={
                        "msg": "Error while touching existing target: %s"
                        % to_native(e, nonstring="simplerepr"),
                        "path": path,
                    }
                )

        else:
            raise AnsibleModuleError(
                results={
                    "msg": "Can only touch files, directories, and"
                    " hardlinks (%s is %s)" % (path, prev_state)
                }
            )

        # Update the attributes on the file
        diff = initial_diff(path, "touch", prev_state)
        file_args = module.load_file_common_arguments(module.params)
        try:
            module.set_fs_attributes_if_different(file_args, True, diff, expand=False)
        except SystemExit as e:
            if e.code:
                # We take this to mean that fail_json() was called from
                # somewhere in basic.py
                if prev_state == "absent":
                    # If we just created the file we can safely remove it
                    os.remove(b_path)
            raise

        result["diff"] = diff
    return result