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diff --git a/mesonbuild/_typing.py b/mesonbuild/_typing.py
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+# SPDX-License-Identifer: Apache-2.0
+# Copyright 2020 The Meson development team
+# Copyright © 2020-2021 Intel Corporation
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Meson specific typing helpers.
+
+Holds typing helper classes, such as the ImmutableProtocol classes
+"""
+
+__all__ = [
+    'Protocol',
+    'ImmutableListProtocol'
+]
+
+import typing
+
+# We can change this to typing when we require python 3.8
+from typing_extensions import Protocol
+
+
+T = typing.TypeVar('T')
+
+
+class StringProtocol(Protocol):
+    def __str__(self) -> str: ...
+
+class SizedStringProtocol(Protocol, StringProtocol, typing.Sized):
+    pass
+
+class ImmutableListProtocol(Protocol[T]):
+
+    """A protocol used in cases where a list is returned, but should not be
+    mutated.
+
+    This provides all of the methods of a Sequence, as well as copy(). copy()
+    returns a list, which allows mutation as it's a copy and that's (hopefully)
+    safe.
+
+    One particular case this is important is for cached values, since python is
+    a pass-by-reference language.
+    """
+
+    def __iter__(self) -> typing.Iterator[T]: ...
+
+    @typing.overload
+    def __getitem__(self, index: int) -> T: ...
+    @typing.overload
+    def __getitem__(self, index: slice) -> typing.List[T]: ...
+
+    def __contains__(self, item: T) -> bool: ...
+
+    def __reversed__(self) -> typing.Iterator[T]: ...
+
+    def __len__(self) -> int: ...
+
+    def __add__(self, other: typing.List[T]) -> typing.List[T]: ...
+
+    def __eq__(self, other: typing.Any) -> bool: ...
+    def __ne__(self, other: typing.Any) -> bool: ...
+    def __le__(self, other: typing.Any) -> bool: ...
+    def __lt__(self, other: typing.Any) -> bool: ...
+    def __gt__(self, other: typing.Any) -> bool: ...
+    def __ge__(self, other: typing.Any) -> bool: ...
+
+    def count(self, item: T) -> int: ...
+
+    def index(self, item: T) -> int: ...
+
+    def copy(self) -> typing.List[T]: ...